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MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG Midget and Sprite Technical - Setting up Su carbs

I've done this lots of times before, but as I am starting out with a brand new set of HS2 carbs I thought I would do it 'by the book', from scratch. I have detailed instructions that were included in the official Burlen parts catalogue from 1994, but immediately these give rise to questions:

1. Checking float height : measurement is given for the clearance between the float top and the chamber lid (inverted). Illustration shows this being checked with a 0.125 twist drill, but doing it that way would give a measure between the lip of the lid that sits inside the fuel reservoir, rather than the lid top above the float. So which is it?

2. For the start point in setting the jets it says to turn them up until they are flush with the bridge, and then wind down by 12 flats. I assume the bridge is the horizontal bar of the carb body. Fully raised, the jet doesn't reach to the level of the alloy bar. - Or do they mean until the jet is flush with the top of the brass piece that is set into the bridge. That brass piece is recessed a bit below the level of the alloy bar.
GuyW

Guy,

I assume you have the modern all nylon floats,
page 18 of the SU manual notes :-

'For the float chamber with the delrin needle and the later all nylon float assembly, the gap should be between 0.062" and 0.187" with the float arm resting on the needle plunger but not depressing it.
This type is not adjustable.'
(the pic shows the lid /float inverted.

The drill stuff was for the older adjustable floats.

I think all the manuals are on line at Burlens site.
The jet part (page 38) notes :-
'Turn the jet adjusting nut/screw up/anticlockwise,
until flush with the bridge or as high as possible without exceeding the bridge height.
Ensure that the jets on multi- carbs are in the same relative position to the bridge of their respective carbs.'
HTH
richard b

Yes Richard, I have that precise wording from Burlen. I do realise the illustration with the twist drill shown is for the earlier type. My floats are the later delrin type, but I was simply using a twist drill as a handy gauge. The illustrations all show the same side on view of a lid so appear to measure the gap from the lid lip rather than invert of the lid. But that is then at odds with the text, though I find it slightly ambiguous.

For Q2, is the bridge level measured as the alloy part, or the brass insert, which on mine is recessed, maybe by about 10 thou.

It perhaps doesn't matter as it's only to get that 12 flats start position, from where they will be adjusted anyway. They just need to be the same.
GuyW

Guy

Swap then for a single carb! HIF44 perhaps? Far easier set up and far smoother running.
Oggers

Oggers, that's what I have on the other car. But I don't want them to be both the same! The idea is to keep this one rather more "period", traditional '50s engineering. So, dynamo, not alternator, points not electronic, positive, not negative earth, etc. And twin HS carbs, not single HIF (it does have disc brakes and a 1098 engine, but shh - don't tell anyone)
GuyW

Do you have the "insubmersible" black float, or the classic yellow-ish transparent-ish ?
Suprisingly, the new insubmersible are adjustable again !
CH Hamon

Cedric, they are white, or almost white. They are either a brand new set of carbs, or if not, then fully refurbished by Burlen. They look new, but there are slight tell tale marks unless they come from the factory like that. Things like the floats should be correct, but I was wanting to check.
GuyW

Guy

I was jesting of course.....Jets, personally I think there are far too many variables to set them by the book. Would it be a question of balancing... perhaps using two interconnecting jam jars full of fluid as a simple manometer and adjust carbs accordingly so the levels in each jar are the same?
Oggers

Even if they are not the adjustable ones, it still worth to check them before they are full of petrol and you see an issue... If I were you, i would still make sure they are closing at the same height between each other...
I read that some people adjust them so that the petrol is just flush with the bridge... Does make sense to me, but no idea how they do it...sorry.
CH Hamon

Ha, Oggers! I do have a home made manometer for when I get to that step. I made it for setting twin Sus before I saw the light and upgraded to a Titan and HIF on te other one. I also rather liked the idea recently explained on here (by Chris wasn't it?) of using a pair of bent wires slotted down into the dashpot pistons. A pair of very neat little divining rods!
GuyW

I usually set the petrol height by removing the pistons and seeing how far down the petrol is in the jet. You want to aim for 3-4 mm down from the top of the bridge. Much higher than that and the petrol is likely to creep up and spill over the bridge, giving you a cycling rich idle and bore wash. If you have an electric pump the ignition wants to be turned on so you have a real time measurement. Also check how often the the pump clicks. Once every 30 seconds is plenty enough. Any more and it's probably drawing air from somewhere. Obviously wipe the pistons down and do a drop test when you screw down the dashpots. They must do a full drop and hit the bridge at the same time. If one is stickier than the other wiggle it left and right as you tighten the screws to find the sweet spot.
f pollock

Guy
Best way to set your jet height is to measure down from the bridge (aluminium bit) and set them both at .055"
If you get one that will actually screw up far enough to be level with the bridge and then by screwing them down 2 turns from the bridge usually gives .060"-.065" but that's usually a touch rich
.055" will be very very close to spot on

With the float height , it's measured from the raised part of the lid that pokes through the gasket into the float bowl, not from the gasket sealing face----If you have the early nylon floats with the metal arm you can 'gently' bend them, but with the later one piece ones the only way is to get into selecting different thickness washers for under the seat where it screws into the lid

willy
William Revit

As I've been having great 'fun' with carbs at the moment I've been following the thread with interest.

In one attempt I used the drop bar part (no idea what it's proper name is) part of a borrowed electronic Vernier to drop the jets to, as previously suggested by Chris (possibly for a B) 0.50" (well 1.27mm as that was easier to read off the gauge) but I'm on rich needles.

For the float height, and other stuff, there are John Twist videos.

I will try Fergus's idea of wiggle (if I understand it correctly) but I've no idea how he can see petrol 3-4mm down but I'm not taking the dashpot and pistons off again to see.

I've become a dabhand at removing the dashpots and pistons complete by using the lift pin to raise the piston enough to get my finger under to lift the whole assembly out being careful of the angle not to catch the end of the needle (too much).

I then place them on marked (F, R) open glass jars that support the piston (and dashpot) circumference and allows the needle to hang safely. Originally I I unscrewed the plastic damper rod cap but didn't bother later, there's a hole in the cap anyway.

Now Guy you might not want to hear this, and it might affect you less in the frozen north, but it's hard to go from total base set up to fine tuning, especially in one go, without a 3-phase cooling fan as the time between the engine being warmed enough to too warm is quite short. You might not want to bother with fine tuning, or only want reasonable running for now and you'll need road testing anyway.

I've only previously had to have a quick fiddle with the carb settings then road testing but going from scratch has confirmed how much warm weather and sunshine we actually get (despite forecasts of cool and very overcast), well in the warm and dry East Midlands anyway. I'm on the BBS now as it's sunny, and warmer than forecast - long road test this afternoon.
Nigel Atkins

Nigel
It 'shouldn't' make any diff. to the idle mixture by having 'rich' needles--Most SU needles in a similar bracket have the first couple of steps the same size--As long as the needles are fitted correctly, flush to the bottom of the piston you should be able to swap needles around without having to screw with the idle mixture

Measuring/balancing/checking fuel levels is easy down the hole---dashpots/pistons out, pull the choke right on, turn the key on to operate the pump and then measure from the bridge down to the fuel level with the end probe of your caliper, if you look real hard at it with the caliper in there as you extend the probe you will see the fuel change shape as it touches---if you're fussy--but with the choke pulled on you can see by eye near enough that they are equal or not--if the float levels have been previously set mechanically and "IF" both floats are the same matched weight all should be well by rights
Remember--to have fun
willy
William Revit

Another hour or so on these carbs and I have to admit I am struggling. To recap: they are a fully refurbished set (they look new) from Burlen. They were shrink wrapped and boxed together with their invoice (£385) which came with the boxes of bits which was my Frogeye when I bought it as an abandoned project. Bought by the previous owner they alone represented 3/4 of the total I paid for the heap of bits at the time.

Fast (actually prety slow) forward to now and although the car has run with these carbs, they clearly are not set right so I am attempting a step by step set up from square 1.

First I had been setting the jet height but then realised that the fuel levels need to be checked first. The floats are the later syle Delrin ones with a spring loaded needle valve.

Following Fergus' guidance on fuel level that it should be 3-4mm below the bridge (the alloy bit, not brass jet guide piece which is slightly lower) mine are no where near. Measuring isn't easy but the front one(photo 2)is around 2mm down at the shallow side (i.e. engine side as the carbs tilt that way). But the rear one is level with the top, (photo 1) visibly spilling down the throttle body a bit. This is with ignition on to prime the electric Su pump. It clicks just occasionally maybe ever 30-40 seconds.






GuyW

What is puzzling is that the rear float clearance looks to be more than the specified 0.062" - 0.187" from the lid top, and yet the fuel level is high. I guess the valve must be sticking?

These floats are non adjustable. I presume the valves would need an extra fibre washer to lower them, and this will then lower the fuel level.


Addendum: That float clearance is 0.125" from rim of the lid that fits down inside the bowl (as Willy advised) so is in spec. It must be a sticking/ leaking valve then




GuyW

Nesxt step, remove and check the needle valve. Nothing amiss there. No dirt, moves freely. I added a fibre washer so the float now is efectively lower - and actually out of spec.

I then emptied carb with a syringe, refitted the top, switched on and waited. Rapid clicks, then a very slow repeating click as the fuel level rose up the jet tube and spilled down the carb inlet! So dispite the lower float it is still overfilling and it seems the valve itself isn't sealing.

Too much pump pressure? Its an Su AUF 214 which should be right for a 1098. Maybe I will need to add a pressure regulater?
GuyW

Yes, your levels look too high, but this in itself wouldn't account for rough running off idle, as the engine's demand for fuel would be exceeded once over 1000 rpm or so. But if your photos accurately represent the fuel levels in the 'primed' condition adding washers would be a quick and easy way to drop the fuel height to the correct level. But your account contains an inconsistency as fuel spilling over the bridge would almost certainly cause the pump to glug more often than once every 30 - 40 seconds.
I would think you have either have contaminated or water in the fuel, or an air leak or unbalanced carbs, so one is leading the other. But
adding a fuel filter before the carbs will help stop a sticking needle valve.
f pollock

I would check the needle valve. I have non adjustable floats and the pump is a Facet regulated down to 2.5. However they do not flood even when I adjust the pressure back up to 5! You mentioned these were recon carbs but some deteriation may have occured over time.
Bob Beaumont

Maybe the pump is going faster then, I didn't actually time it and am pretty deaf so its not a loud noise anyway. I can try that again and time it.
When I watched, the fuel rose up the jet tube quite slowly and steadily until it spilled out the top. And that was after fitting a fibre washer under the jet.
Fuel is about 2 weeks old, and then another gallon added yesterday.
Unbalanced carbs is likely as I haven't got to the stage of getting it to run well enough to adjust them yet!
GuyW

Bob,the needle valves look pristine. I was hoping to find a speck of dirt but nothing. And as they are new they clearly haven't got wear ridges. Floats are also new and pivot freely. If there's a fault it would have to be a manufacturing one so I will go and dismantle and check for casting burrs on the nylon.
GuyW

Do you have the valve with the nylon tip ?

There is also different version...do you know if you have the correct one for your car (should be as you have the good bowl height) ?

Are your jet new ? If no, fuel lines could be perished from inside...

http://sucarb.co.uk/float-chambers-spares/needle-valve-kits/standard-needle-valves.html
CH Hamon

What is strange to me is that you don't have the same fuel level for the carbs...The two float height are the same ?
If yes, are you confident in the condition of your fuel lines and no obstruction for fuel to navigate to one carb and between the carbs ?

Might be one of those small problem not so obvious and not repetitive but annoying to find :/
CH Hamon

One last idea... Please guys stop me if i am not smart (at all)...
Wouldn't be an idea to just remove the two lids, fuel the two chambers until the same height of fuel in the two chambers, and see if it is the same height in the two jets ? Then you will know if your issue is more around jet/carbs or float/incoming fuel....
CH Hamon

Have you got another set of needle valves/seats - I have problems with them not seating/sealing on more than one occasion.

Try blowing down the feed pipe into the float chamber when inverted and see if it seals.
richard b

Cedric the carbs, pump, tank and all fuel lines are new though that doesnt mean there isn't a problem!

I suspect these spring loaded valves. If I take the lid off and invert it and then switch on the pump, the weight of the float itself isnt enough to completely stop the fuel flow. If I then press down on the float it eventually stops flowing but only after the sprung part of the valve movement is fully used up and I am directly pressing the valve shut. That doesn't seem right.
GuyW

What is Archimede saying ? :)

Do you have the nylon tip on the seat ? As said by the others, i had issues too, and new valves with nylon tip (sold by Burlen) solved all of it.
CH Hamon

Richard, yes I think I have some spare valve pairs and I have probably got some of the normal floats with the metal bit that one can bend to adjust. I may have to start mixing parts tomorrow though it seems wrong when these are refurbished direct from Burlen.
GuyW

Cedric, no these valves have a steel pointy end. It doesnt match onto a conical surface though, but goes into a circular hole in the brass piece. In theory, if the hole is accurately round, the valve point should automatically self centre on the hole and seal all the way round. If its machined accurately.
GuyW

I am surprised Burlen doesn't refurbish them with nylon tip, as it is what they are selling on their website...

I do agree that it had - and will - work for decades, but to my mind, it is a nice upgrade as nylon is soft enought to compensate some light deformation, and "should" last longer...
CH Hamon

Aha when I refurbished the HS4's on the Frog I purchased the non sprung type. I think I recall reading they were more reliable but don't quote me!
Bob Beaumont

An aberration then perhaps, by Burlen, around 12 years ago. I think that is when they were bought. I may have some spares to try. If not then I will see what Burlen can currently supply.
GuyW

Guy,
my carbs are (supposed to have been) new 10 years ago so (about) same as yours, £350.73 excluding (17.5%) VAT from B&G.

Quick points -
. are you sure the jets are fully screwed up into the carb body as they look a lot lower than both of mine
. you do not need a fuel pressure regulator (advice I've been given, more than once, for about 30 years)
. the floats should not need any adjustment, I read somewhere someone never found one to be wrong from SU
. are you going to trust that braided fuel hose?
. you've probably already seen this but as a reminder of the types of needles and seats - http://www.youtube.com/watch?v=v9QI3NlvwiY
and wrong size - http://www.youtube.com/watch?v=pVX_JClyeDQ

Nigel Atkins

Willy,
thanks for info, never thought of the pulling the choke right down. If you could see through my eyes you'd realise that you can't really see that well through my eyes (but they're still up for donation).

I've never, ever, had fun working on my cars, I'm not sure anyone else has either judging by the quality of some of their work, at least I balls it up at very little labour cost.
Nigel Atkins

Thanks for suggestions Nigel.
I guess my jets look lower than yours as the photo is taken with the choke fully out - to make it easier to measure fuel level.
My floats are the non adjustable type, unless one started adding fibre washers to pack them out. They should be correct ex Burlen, but they are not the same. I don't know if this is a problem.

First I need to get the valves to seal properly. I have established that they are not sealing even with the floats fully up. Its not clear to me why as the valves are new.
Burlen now only list the Vitron tipped versions, but are out of stock of the spring loaded variety. Are they interchangeable?

I've no idea if the braided hose will last. How could I tell in advance?
GuyW

Guy

I have Vitron tipped and they behave ok.

I did worry about the Braided hose failing internally as there is no way I could see of easily testing. I had a NOS one and it looked the part but given all the comment about fire in the classic car press, I decided to replace it with hose which would cope with ethanol.
Bob Beaumont

This hose came with the carbs so from Burlen one would expect quality. But then ethanol wasn't such a problem 12 years ago. The compromise answer would be to get a new ethanol resistant hose and slip the braiding over it.

Why don't people use that clear plastic pipe with the criss cross mesh walls? Looks crappy I know, but that is what we used to use.

I think I will buy some Vitron tipped valves. But I am not over confident that this will solve the problem. I imagine the steel tipped ones were abandoned because of leakage from wear ridges, but mine are brand new. Why would theyleak?
GuyW

Possibly a bit of corrosion around the seat??
Bob Beaumont

- Do you have the same issue with the two float chamber ?
- Does the valve seat close when you blow through them inverted ? (I was doing the same in my kitchen Richard :D)
- On the same concept, I also tried to blow through them, and at the same time, dive the float in a glass full of water to see if it seals... (You should see the look my girlfriend throw at me...)
- Don't you have a 1275cc too ? Can you change parts ? I know it is not proper way of doing, but...

I agree with your view of "why new ones leak"... So if in fact, your seats work properly, then I would bet on Nigel and the fuel pressure: too high pressure for the seats to work would make a lot of sense...if you have a more powerful pump than the standard SU
CH Hamon

I hope the braided ones are still ok if marked 'petrolflex' as I recently bought some from B&G for a 'B' as they have threaded ends and normal tubing cannot be connected without chopping off the fittings.

Yes Guy some of the piping I'm replacing on the B is the clear braded type (was clear 20 yesrs ago and now rock hard'

The leakage could well be the seats - mass produced and only need a slight burr/raised bit and hard needles not seating.

Could try 'bedding the needles' in onto the seats or if you are changing them any way a light tap.

With clack valves on steam engines using ball bearings its not unheard of giving them a light tap onto the seats with a soft drift - some now run hard rubber - its a long time since I built one.
richard b

Guy,
it might be my poor memory, or even perhaps my carbs but I meant the outer part of the jet, rather than the part that moves (and can stick!) is seated higher on mine, mine almost look above the body bridge but aren't.

The needles seemed to change with time (and fashions?), hence my JT vid link and be interchangeable, but I'm no expert.

I thought about renewing my needles and seats (and jets and piston needles) but Burlen were out of stock, for sometime now as Cedric reported this a while before. They may be in stock with other suppliers but when I looked at the viton tipped needles and seats on mine to me they looked fine after 50+k-miles.

I, and at least one other person I know so not just me, found Burlen less than helpful to deal with, I got a chap from 'sales' that was miserable, bored, and with no initiative I had to tactfully suggest possible actions.

Andrew Turner is the person I've heard recommended a few times, he also sells SU parts (easier to deal with than Burlen I was told) and on his website Home page offers - "We are happy to offer technical advice both at the shows and over the phone." so you could him for advice and parts. - http://www.su-carbs.co.uk/

AFAIK if your petrol pump is an SU AUF214 and is working correct you'd have no problems with pressure.

I use the smaller clear plastic petrol filter in the engine bay to see how much petrol reaches that point, and as a filter.
Nigel Atkins

Guy,

Currently on E bay the 'Bhive' have one set only of Viton tipped needle/jet.

R.


Also Minor suppliers

https://bullmotifminispares.com/1839/su_needle_valve_and_seat_wzx1100_vzx1100_ca90_gsu101_aud9096_wzx1100a
richard b

Guy
With the metal needles ,as mentioned by Richard, I'd give the needle a light tap or two into the seat to bed it in--The Grose ball bearing needle/seat sets suffer from weepage like yours when they're new and a little tap,tap sorts them out
It sounds like a leaking needle and seat to me

You could check it by swapping the seat assembly over into the other carb. and see if the fault follows, I reckon there's a little dag on the edge of the sealing seat, maybe if you have some 2nd hand seats ,try them with your new needles if the little tap doesn't doit

willy
William Revit

Thanks, more useful advice to try. Slightly annoying is that the float pivot pin on these is a burred/ interference fit that needs to be pulled out and in again with long nosed pliers, needing a fair bit of force to do so. Unlike all the others I have had with a brass pin that just drops out on the floor if you are not careful. But once the lid is on neither sort would come out anyway so I don't know why they have made them harder to remove. Tiresome as any attention to the valve needs r & r of the float. So I will try tapping and swapping etc but it all takes time!
GuyW

Float pin could be storage/age minor surface corrosion (or whatever the correct term is) as I've also got some old unused for very many years carbs I was given and the pins came out same as with the newer ones on my car by a squirt of PlusGas and a few very gentle taps with small light hammer (I made in metal work when at school).

I was given the carbs as I wanted one lid screw that another mate lost.
Nigel Atkins

Yes the float pin comes out with pliers or gentle tapping with a pin drift. But it's a faff when trying multiple combinations all of which need the float to be removed and replaced for each test.

Anyway, I have finally got the valves to close. I still have my twin S.U s from the 1275 although unused for 20 years or so. Plundered various bits but the thing that made the difference was the float. It looks the same as the new ones except the platform that operates the valve needle is nearer horizontal at the close point. I think the new ones were putting a lateral load on the pin causing it to lean slightly as it entered the valve orifice. Pump pulse interval now timed at 2.41'mins for 1 pulse, 11.10' for 4. Fuel level around 3mm down on each and jets both set at 0.057" down which was about 10 flats.

And battery arrived too! And Nigel, you will be thrilled to hear that it is fully charged! What a day, even the sun has appeared at long last. 😁
GuyW

Conversely it could be the valve needle sitting at the wrong angle or height - get the pliers out and try various needles against that float.

Of course being independent "precision instruments" their components don't need to match each other.

Good news about the battery arriving and being fully charged, best get it out of the sun then, and you'll now be able to find how intermittent, or not, the proper operation of your timing gun is. Take you back to the days of going to "the flicks" to see the latest Charlie Chaplin film.
Nigel Atkins

Nigel

Nothing in the good book on carbs?

I do hope you are not tinkering or upgrading rather than carrying out regular servicing!

Cheers
Mike
M Wood

Tried 3 different needles, 3 valve seats and 2 floats and most permutations of those. Best one was old float, old valve brass body and new spring type steel tipped needle. Only it's leaking again. I've ordered some Vitron tipped ones.

Strobe is in bits, awaiting delivery of new condenser as that seemed the likely culprit.
GuyW

Grrr!
I ordered a pair of Viton tipped valves from Bullmotiff mini spares, in the hope that these would cure my float chamber flooding problems.

Last Tuesday I got an order notice email saying they had been dispatched on a 48hr delivery, so I had been looking forward to getting the carbs sorted. But the order hadn't arrived so I emailed them. Today I got a lengthy detailed excuse of why they are currently out of stock, conveniently ignoring the fact that last week they told me they had already been sent.

Grrr!

GuyW

Guy

How frustrating, both the fault and the quest for sourcing replacement parts.

Have you seen this uprated Minispares product?
https://www.minispares.com/product/classic/CA90.aspx

(And: https://www.minispares.com/product/Classic/Fuel/Carburetors/Spares/WZX1100A.aspx?130203&ReturnUrl=/product/classic/CA90.aspxBack%20to & https://www.minispares.com/product/Classic/Fuel/Carburetors/Spares/AUE266.aspx?130203&ReturnUrl=/shop/classic/Fuel/Carburettors.aspxBack%20to%20shop)

Cheers
Mike
M Wood

No Mike, I hadn't seen that modified valve, but had ordered the WZX1100A version which is what that minispares site recommends for when there is ethanol in the fuel.

I was just annoyed that the bullmotiff company should accept my order, take my money, say they were despatched, and then a week later give me a long spiel about how they were struggling with suppliers because of some virus or other.

They have belatedly offered to refund.
GuyW

Hi Mike,
sorry I missed your post.

I've done so much that without looking I can't remember what the good book says, but I've done it at least twice on that method this time round.

Unfortunately I made the stupid mistake this time of thinking I'd improve things but fitting the standard parts that weren't on my car whilst I cleaned and sorted my carbs as - once again - the carbs had to come off for unexpected distress work.

What really, really, no really, pisses me off is that the car was going so well from service setting of carbs just before everything went mammary glands skyward with ancient technology assembly in engine.
Nigel Atkins

Guy,
I thought about renewing the seats and needles on mine but saw they were still out of stock with the manufacturer and was unsure of supplies elsewhere. But good job I didn't as they looked fine when I inspected and seem to work fine.

I also thought about replacing the piston needles and jets but again they were out of stock with the manufacturer, and again I was concerned about supplies from elsewhere. whilst I think at least one set might need replacing the carbs aint coming off again I'll just drive though it unless it gets bad.

SU Berlen did supply some parts but you wouldn't believe me if I told you about them.

I wish I'd contacted Andrew Turner as a friend in the club told me about him years ago but I didn't realise he also sold parts until another mate told me his company buy through Andrew Turner as he gives discount for trade volume unlike SU for them (lots of part over a year).

Stock levels, what the computer or sales/storeman tells you can be three different things at once, more so with some companies than others.
Nigel Atkins

Nigel, I can well understand there may be discrepancies between stock level records, web site offers and what someone might say over the phone. It's easy for such systems to get out of sync and that can be forgiven.

My gripe was about being sent a despatch confirmation message saying that the items had been sent, when they hadn't even though they have drawn the payment. Even that could be excused but not then concocting a tale and hiding behind coronovirus issues to cover what was clearly either a mistake or a lie
GuyW

Guy,
I totally agree, perhaps sometimes some systems give a dispatch notice as the dispatch is in preparation, for the picker to get to the parts location to find it ain't not there. Then an immediate notification of the out-of-stock should be sent to you.

Being cynical, perhaps it helps with charging for the part for it to be possibly in stock and in preparation of dispatch for as long as possible before finding it's not. But never ever underestimate the potential for mistakes and inefficiency in the company, its systems, personnel and particularly managers/owners.

Nigel Atkins

Well I tried the minispares site but that came up with a low stock alert so I rang them. Apparently "Low Stock" actually means No stock, with the items on back order. He offered their other special high- flow valve but agreed that if I am having problems with flooding float chambers then it is the Vitron tipped ones I need.

Frustrating, but as I am not using the car it doesn't really matter. Its not as if it's my only car and daily driver
GuyW

You checked, I didn't but I got got the impression from looking on a few sites and the fact that they were stock from when Cedric enquired with the manufacturer that other stocks elsewhere might be 'low'.

Others might have stock of course.

I'll remind you that Andrew Turner sells parts and offers advice, I'd suggest you ring him. (I've never dealt with just going on what others have recommended.) - http://www.su-carbs.co.uk/
Nigel Atkins

Nigel, I hadn't heard of Andrew Turner before you mentioned him. He doesn't seem to have an on-line shop, but I have emailed to see if he has any of these valves in stock.
GuyW

Guy, if you can then phone him, more info and communication from ringing than email I find - but then I am a very charming person.
Nigel Atkins

And presumably not deaf?
GuyW

Guy

Looks like there may be a delay in getting these needles.

I will have a rummage, as I renewed the float needles as a matter of course and I recall I kept the old ones (why do we do this??). They were working fine when I removed them.
Bob Beaumont

Guy

Some standard needle valves for sale, looks like two in stock: https://classiccarbs.co.uk/product/vzx1100-needle-valve-kit

Cheers
Mike
M Wood

Thanks Mike, you are trying hard for me! It is appreciated but I am specifically after the Viton tipped ones rather than standard. The illustration does look like they are tipped, but the part number is missing the A off the end which I had previously thought was the identifier. I will need to ring them tomorrow to check if they haven't already gone by then!

Thanks for your offer Bob. It would make me feel guilty taking your stock spares. You never know when you might need them.
GuyW

Guy,
I knew you had issues with your hearing but thought you could use the phone.

I don't think you need put any significance to an 'A' on the end of the part number as SU only list VZX 1100 - http://sucarb.co.uk/needle-seat-kit-viton-tip-0-070in-now-vzx-1100.html
Nigel Atkins

Well to be honest, Nigel, I can use the phone but really struggle these days so I prefer not to.

I wonder then, why some suppliers add an A to that part number.
GuyW

Try following SU Burlens numbers on their website and the Search facility, to be completed later it seems to me.
Nigel Atkins

In light of the earlier travails highlighted in this thread, perhaps A stands for 'available' or quality that is 'acceptable' (hopefully not 'atrocious')!

I had looked to see if other suppliers such as Somerford Mini stocked needle valves, but they only listed as part of a rebuild kit (may be worth a ring to ask?). The HS2 carb (and HS4) has to be one of the most common SUs around, so parts availability is odd and a concern, as well as quality.

I was a bit startled to hear of quality issues with Burlen parts as this would be OE now. Which parts? New carbs? Have we now entered the realm of rebuilding old carbs the best and only thing to do, and to try to identify and source good parts to do so? I have found old SUs capable of being revived and rebuilt from being poorly serviced, incorrect parts and even damaged. Are old SUs now like 'Italian Webers' in being the ones to go for?

What needle valves are being made/sourced in N America, Australia and New Zealand I wonder?

Cheers
Mike
M Wood

Postie has been and it looks like we are back in business!
Fingers crossed 🤞 that these solve the flooding problem and I can then get on with setting it up properly.


GuyW

Magnifying glass out to check finish quality then.

I've just looked, I think it's a 1BA socket you need for the seat, but an AF will fit well enough, I forget the size now.
Nigel Atkins

Mike, We have a mob called Fuelmizer here that sell fairly good quality stuff, one being good quality vented ignition points
Their SU needle and seats are also good but a bit(lot) overpriced at $44 each

Midel sell 'genuine' SU parts-

http://www.sumidel.com/shop/category/su-carburettor-needle-seats
William Revit

Frustrating 3 hours, and still having problems.
Initially with the viton tipped valves fitted I got an even worse session of flooding. This time petrol was coming up out of the carb jet like a fountain! A bit of jiggling and that subsided and they both then seemed to seal ok although I am still getting a very strong smell of petrol and I am not certain how reliably they are closing.

Anyway, that was behaving itself sufficiently enough to get it running but it is still misfiring and farting and needs me to continually pull on throttle cable to keep it running at all. So I spent the next two hours checking and where necessary changing electrical stuff. I have through this followed the golden rule of only changing one thing at a time before a retest but so far nothing has improved it at all.

Things I have swapped out:
Rotor
Dizzy cap
Plug leads
Coil
Low tension coil to points wire
HT coil to dizzy cap
Plugs
Plug connectors

There are a few more things I can try tomorrow, but so far I am no further forward.
GuyW

Guy, does more or less choke make a difference?
Just wondering if its fuel rather than spark related.

Trev
T Mason

To complete the electrical condenser and points - possibly then try a jury rigged supply of new petrol (Prop would be saying gas is rubbish these days !)

R.
richard b

What's the condition and operation oof your fuel pump, lines and filter?
M Wood

Guy
If it's continually missing and farting and you have to keep pulling throttle on it 'might' have a major vac. leak somewhere
Is the manifold gasket ok ,and tight, any vac hoses off--?
William Revit

Morning all,
Trev it's really not running well enough to determine that yet, it's all I can do to keep it turning over.

Richard, they are new points and condenser so should be ok. But I have a spare complete dizzy to try today. Fuel is fresh but a jury rig might be one way of eliminating possible high fuel pressure.

Mike, it's all new, tank fuel lines and fuel. Pump is as a reconditioned electric S.U but the problems I have had with leaking fuel valves does make me wonder if the pressure is correct.

Willy that's sideways thinking - I haven't checked but will today.

The odd thing is when I first ran it it was passably ok. Not set right but certainly good enough to drive up the road 50 yds and back. It then sat on the driveway and ran for 20 minutes on its own whilst I checked it over for leaks, oil pressure and that the guages worked.
GuyW

I feel re-inspired with your various suggestions to have another go this morning. Just a couple of domestic chores to see to first today.

One other thing - I ran it in the dark last night to look for sparks. Nothing, except if I poked at the coil LT Spade connector I could induce a spark between the spade and it's rivet. I don't think that is my running problem as it ran badly on a spare coil too - unless that one is also faulty . . . .
GuyW

It is starting to sound like it might be an induction or head gasket leak. It's been through at least one heat cycle and may need nipping up. Whizz it round with the plugs out and check the bores are dry.
f pollock

Compression test is one of the things on the list to do. I did one before its first start and they were all 4 at 155. Consistent, but possibly a bit low but it is a basic 1098 and has been standing for 10 years since its rebuild so I wasn't worried by that.
GuyW

Compression test: 168,160,164,164 Slightly up from before it ran at all which is what one might expect
Carbs not flooding today
Plugs very sooty
Changed the rotor arm again
None of this improved running

Next was to swap the dizzy. It has been on the original Austin Sprite 25D one as I dont know what my other spare dizzy is off. Its a DM2. But I realised that is what it ran with briefly a couple of weeks ago, so I fitted that back. i just turned it so the rotor arm was at #1 lead as I could feel compression building on no 1 cylinder so not accurately timed.

And ... ( drum roll) it works! Ran well, even the timing seems just about right. Running well enough to then set carb balance and adjust tickover. Just need to set the mixture strength, doing the carb lifting pin thing though I presume the air filters really need to go on first for that.

I need to investigate the 25D dizzy to at least satisfy myself what the fault was.
GuyW

Advance springs broken / advance seized ?
richard b

Quite likely. It had new points and condenser, but you can never be sure.
I will look later
GuyW

Bob weights and springs look fine on the bad-running dizzy. Little earthing wire to the base plate is very floppy but checks out OK for continuity with a meter. All looks ok and as it should be.
Got to suspect the new condenser I suppose.

Anyone know what my DM2 dizzy might be off?
GuyW

Guy, I only trust the Bosch condenser, they are reliable in the heat and resistant against vibrations. It is bigger and not easy to install in the DM2.
Flip
Flip Brühl

Guy

DM2 distibutor's are used on A series 948cc engines amongst others. It was standard on the frogeye(DM2 PH4)The lucas part number is 40561 . Also fitted to A30/35/40 Morris Minor.
Bob Beaumont

That makes sense, it will have been in one of the boxes of bits, even though the proper 948 engine wasn't with it.
GuyW

Given that I don't want to buy a new dizzy and am not going electronic, would I then be better to use the DM2 designed for a 948cc, or fix the 25D which was off my 1275. This car is a 1098.

The advance weight arm on the 25D is marked 11 (degs of advance, I presume).
How much does the vacuum advance add to this?
GuyW

Lured from hibernation by the sunshine, you know!





GuyW

Looking like a showroom new car.

Note that dis' degrees are times two for engine degrees. So dis' cam at 11deg is 22 crank degrees. Then add in the static.
anamnesis

Ah, thanks. I had forgotten that.

What about the vacuum advance? Does that get added on top, or is it effectively 'engulfed' at higher revs by the dizzy bob weight advance?
GuyW

Really nice.

Without what goes behind the rad grille for a start I thought it was a more modern replacement one, so clean looking.

Loads in the Archives here and in Bs about dissy curves, I've no idea which matches to which engine but from JT IIRC the later dissys (for Bs at least?) got to deal more with emissions than performance outright. Of course the B engine remained the same capacity but did change similarly in line with Spridgets.

You'd probably want the dissy with the most performance development to match your engine period as the 1098 were before much emissions and economy of the 70s.

According to the leaflet with my 123 fully electronic (no farting about) dissy the 40561 midget MK I, 1961, 948 cc, Engine no. 9CG ; distributor-type DM2P4 has a entirely different settings curve than the 1098 and 1275 but I'd guess the DM2 or 25D could be adapted to suit(?).
Nigel Atkins

I'm becoming more interested in this as I move towards getting the engine running. I always wondered if vacuum advance had much effect but, reading about it, it certainly seems to especially at lower revs and when initially accelerating (due to higher manifold vacuum I presume). AIUI the centrifugal advance takes over more at higher revs, especially initially as a (designed) weaker spring leads to increasing advance but then is restrained more by a (designed) stronger spring which takes over.

So it seems the vacuum and centrifugal advance add together. However, as has been documented, modern fuels are different and it could be that an older "stock" distributor won't necessarily produce the ideal advance anyway. Combine that with worn centrifugal springs and leaky/ sticking vacuum units and it all becomes a tad unpredictable. I suppose that is why people go all electronic.
Still, if an engine achieves reasonable performance with no or minimal pinking, I'd be happy as I'm sure you would be Guy.
Bill Bretherton

This is as good a description as any I think.

--------

Vacuum Advance.
Vacuum advance has absolutely nothing to do with total timing or performance, as when the throttle is opened, manifold vacuum drops essentially to zero. At idle, the engine needs additional spark advance in order to fire that lean, diluted mixture earlier in order to develop maximum cylinder pressure at the proper point, so the vacuum advance can (connected to manifold vacuum, not "ported" vacuum) is activated by the high manifold vacuum, and adds spark advance, on top of the initial static timing setting. The same thing occurs at cruise, the mixture is lean, takes longer to burn, the load on the engine is low, the manifold vacuum is high, so the vacuum advance is again deployed.

When you accelerate, the mixture is instantly enriched by the accelerator pump, burns faster, doesn't need the additional spark advance, and when the throttle plates open, manifold vacuum drops, and the vacuum advance can return to zero, retarding the spark timing back to what is provided by the initial static timing plus the centrifugal advance provided by the distributor at that engine rpm; the vacuum advance doesn't come back into play until you back off and manifold vacuum increases again as you return to steady-state cruise, when the mixture again becomes lean.

Vacuum advance, responds to engine load and rapidly-changing operating conditions, providing the correct degree of spark advance at any point in time based on engine load, to deal with both lean and rich mixture conditions.

This all holds true for modern cars, too, but in their case, the timing is normally monitored by a position sensor on the crank pulley or flywheel that let's the ECU know where the piston is at in terms of ° BTDC. It also uses Manifold Absolute Pressure (MAP) and a Throttle Position Sensor (TPS) to look at load/fuelling needs, and with this can then set up the advance electronically with much more resolution, resulting in improved tick-over and cleaner, more efficient burn of the fuel.

https://www.mginfo.co.uk/upgrades4mgs/Engines/ignition_explained.html
anamnesis

But that queues the debate ported vs manifold vacuum, because most a series Spridgets run ported vacuum.
anamnesis

Guy, if it runs well with the DM2 I would go with that. I have a 1098 and when I bought the car it had a late Morris 1000 engine in it which I changed to a Midget one but used the dissy from the 1000. The body is marked 25D but when I installed electronic ignition I discovered the guts, or at least the base plate was a DM2. I have not checked what advance mechanism it has but would think it's a fair bet it's a DM2 and the car runs really well up the entire range so I have left it alone.

Trev
T Mason

OK, I will probably stick with the DM2 for now, at least until I have been able to run it for a bit to assess.

That description 'anemnesis' copied of the operation of the vacuum advance fits with my thought that this advance moves timing forward from the static/ tickover setting, but then as revs increase this is overtaken by the centrifugal advance. So unlikely that you would add all of all the 3 together at any one time (static + vacuum + centrifugal) There might be some oberlap, but generally it would be static plus either one of the other two. Is that correct?

Nigel, there is nothing missing from behind that grill. That is how they are, so for cars with lighter coloured paintwork you get that effect of seeing parts of the background of the grill - especially in direct sunshine. I think some owners paint those areas in black, but that's not how they came from the factory.
GuyW

This is the info off my 123 dissy list of curves. I don't know if it's strict original curves or updated to allow for modern changes though but it should give an idea of the differences.

DM2P4 (40561) – Engine no. 9CG
Advance 500-1000 rpm* 10.0
Advance @ 2000 rpm* 23.95
maximum @ 5000 rpm* 34.0

25D4 (41270) – 1275 cc, Engine no. from 12CC/Da/H11639 on; 12CE & 12V
Advance 500-1000 rpm* 10.0
Advance @ 2000 rpm* 14.5
maximum @ 5000 rpm* 28.0

* degrees advance and engine speed both relate to the crankshaft

ETA: Guy, it's probably just the photo angle of the grille in the sun and everything being so new and shiny, plus I'm not used to seeing the higher end of the Spridget range - or being allowed near them, a surprising amount of light can be lost through binocular lenses.
Nigel Atkins

Vacuum advance adds to both static and centrifugal. That sounds like too much advance, but it only happens when the engine isn't under load, such as at idle or when cruising at higher revs but with the throttles only slightly open.

When the throttles open more, vacuum drops off, and timing retards. --- As I understand it.
anamnesis

From the horses mouth.

http://sucarb.co.uk/technical-su-carburetters

Scroll down to "The H type carburetter".

"On many cars it is found desirable to use vacuum operated ignition advance to obtain optimum part throttle consumption figures. The take-off point for this vacuum is arranged slightly to the air intake side of the butterfly, and in such a position that opening the butterfly allows the throttle disc to pass over the vacuum take-off point so that it then communicates with the manifold depression. By this means the vacuum is small at the distributor during idling and full throttle conditions, and is large at part throttle, being at a maximum when the throttle is open a few degrees."

anamnesis

Trev, that would be my approach- if it runs Ok, leave it alone.

I now see that the vacuum and centrifugal advance only add together sometimes. It's complicated, isn't it.

Incidentally, what is the difference between ported and manifold vacuum?
Bill Bretherton

Amen, I think that's my point, though I am only speculating. At mid engine speeds, on light throttle, the vacuum provides its max advance plus maybe a bit of centrifugal advance ( the light spring). On full throttle the vacuum drops off but the centrifugal takes over as revs rise. It's actually a very clever mechanical balancing act, well before fancy electronic programming.
GuyW

Ported vacuum is taken from the throttle body of the carb, just where the butterfly crosses the hole for the vacuum pipe. Manifold vacuum is taken from the inlet manifold.

See this.
https://www.britishvacuumunit.com/ported-vacuum.html
anamnesis

Anam keeps getting changed to Amen ! Predictive text, rather than meaning I am agreeing, or venerating for that matter!
GuyW

Anamnesis, thanks. I suppose it's rather obvious when thought through but I wanted to be sure!
Bill Bretherton

There's a very big difference between manifold and ported vacuum when it comes to oil breather problems but I wouldn't mention it here in case it sets someone off.
GuyW

Bless you my son; --- for not pouring oil on troubled waters. 😉
anamnesis

It is well worth the time to get the advance curve matching that specified for the engine. While sometimes there is little to be gained, at others the difference in performance can be major - or worse,
if seriously over advancing it can shorten engine life too.

In principle it is simple to do.
Get the centrifugal advance figures from the workshop manual.
Check whether crank degrees or distributor degrees. If the latter, double them.
Add to each the static timing figure.

Plot them on a graph and run a line or lines through the points.
Discinnectvthe vac advance and with the aid of a helper on the accelerator pedal measure and note the total advance every 1000 rpm until it stops advancing or you reach 5000.

Plot the results on your graph and draw lines through them. Usually 2 lines one for each spring.
While this can be done by just comparing the figures, plotting a graph is very useful. The slope of the graph lines are determined by the springs, the start and finish points are determined by where the springs start and stop acting, including when the limit stop kicks in.

From this you can determine whether the springs need changing or not, and whether their length needs adjusting do they kick in at the right point. And whether the limit stop needs adjustment.

If you don't fancy doing the adjustments yourself you can of course get it done for you. We have found the variation from spec to be more than 10 deg on a significant number of occasions, with the record being about 20 deg. All this while the distributor was set at the right static or idle timing. We all know how much difference timing out by 10 deg makes. So a well worthwhile exercise.

A couple of points to finish with:
DM2 has a different set-up from 25D which is a bit more complex to compare to spec as mech geometry has an effect on advance rate.
And it's useful to measure the total advance with the distributor in the car (compared to on the bench) as drive train wear can alter the total advance recorded. Paradoxically this seems to add advance, I have some theories but no definite explanation. But it is certainly a real effect.

Paul Walbran

This thread was discussed between 11/09/2020 and 29/09/2020

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