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MG Midget and Sprite Technical - 1500 lacks power

I just rebuilt my 75 -1500 midget. It was running like a dream. I ran it through a break in period in my drive and the took it for a short spin. First time around the block no major issues. A few days later around the block it lost most of its power and I could barely get it up the drive only by reving the %^&* out of it. Now it idles extremely rough almost like it is out of balance. Timing is tough to keep and my dwell is set at .015 with a feeler. Do you think i should replace the points, condensor and coil or should I pack it all in and also renew the distributor. Or... do you think this could be fuel side?
T Leach

I guess this could be just about anything :-(

Start with some basic checks and build up as you confirm things are as expected.
I would do the following..
1, Compression check to check for HGF
2, fuel delivery to carbs ie is there enough
3, check for a spark at each plug, any plugs showing signs of fouling?
4, Bypass the ballast in the loom for a short time to eliminate it.
5, check there is a good eartn from the coil -ve to the battery when the points are closed
6, replace points/condenser with electronic unit (or try replacing the condenser if you have one).
Only after this would I consider replacing a coil

Best of...
MGmike
M McAndrew

Depending how long it has been laid up, the fuel system could be at fault too.

Perished rubber on the inside of fuel pipes, rust in the tank getting into carbs, pump not delivering sufficient etc.

As well as ignition as said above.
JB Anderson

2 checks you can do without even getting out of the drivers seat.
When it is spluttering, does the rev counter needle thrash around in jerky movements? - indicates a fault in the LT side if the ignition system - wiring,points,capacitor,ignition switch. Not fuel related unless of course you have more than one unrelated problems!

Second check is to pull choke out about half way. If it momentarily runs better it suggests a low fuel level in the carbs and likely to be a fuel delivery problem. Blockage, faulty pump or just a nearly empty tank!

Neither check tells you exactly what the problem is, but may point you in the right direction and avoids the worst thing which is to start to alter and adjust things at random.

The next check l would do is take the rad expansion bottle off and look for rising air bubbles which could indicate a head gasket failure. Look also inside the oil filler cap for white "Mayo"

So far you haven't altered anything, not needed any tools, spent no money and probably wasted no more than 5 mins tops but could well be narrowing down to an accurate diagnosis already.
Guy W

Sounds like.a.classic case of a blown bead gasket

Did you get the correct HG ?, 2 differant hg for the 1500.. the differance is in the firing rings

Prop
Prop and the Blackhole Midget

Thank you all for your advice. I will go through this systematically. Gas quality and gas lines is not an issue. I am concerned about the head gasket because I just replaced old with new and I had no idea there are two choices. I hope like heck I did not get the wrong one. I did think that I may have installed the new one upsise down and backward.
T Leach

If you bought a HG for a 1500 Midget, then you are fine. Any 1500 gasket should work. It was Spitfire 1300 and 1500 that were slightly different.

Also, it is impossible to get the HG on the wrong way round due to stud hole locations etc.

That said, it might just not have taken correctly. It happens.

Malcolm
M Le Chevalier

Thanks for the clarity malcom

Prop and the Blackhole Midget

Just commenting on Guy's point about pulling the choke out a little to see if that improves things. It did in my case (in a pevious post).

But surely, if there is an inadequate supply of fuel to the float chambers, pulling the choke out would make even greater demands on the fuel suppy.

Dave.


D MATTHEWS

Dave, on the SU carb pulling the choke cable lowers the jet. If fuel level is a bit low in the float chamber it allows fuel to reach the lowered jet and be drawn through by the air stream. For a moment, it reinstates the fuel supply and the engine will pick up again for a fewm moments.
Guy W

I did a compression check and got zero (0) on 1 and 2 and 180 on 3 and 4. I pulled the head and confirmed a blown head gasket between 1 and 2. This was a brand new gasket. I have uploaded two pictures. Is it possible it was in upside down and backward. I am at a total loss as to why it blew out again??? I was just breaking things in. I know I keep on about upside down and backward but have a look at the burn hole beside #1 in the pics.#1 blew out at that point. I am confused.

T Leach

I tried twice with the basic gasket like the one you have in the picture and failed each time between 1 and 2. In the end for the third time I sourced a Payen gasket from Rimmers. No problems since.

:-)

Good luck, Dave
Dave Squire

Ouch!

OK... I am doubting what I said about it being impossible to put a 1500 HG on the wrong way.

Those two cylinders should be 3 & 4, the tab on the gasket indicates the back of the engine.

Malcolm
M Le Chevalier

Here's one I blew earlier! (Due to my own stupidity when filling the coolant).

M Le Chevalier

And a link to a discussion on 1500 head gaskets we had in April of this year, some useful general advice/things to know.

http://www.mg-cars.net/mg-midget-sprite-technical-bbs/midget-head-gasket-help-replacedblew-same-day-2015042315154618084.htm

Malcolm
M Le Chevalier

Malcolm is rigt. And the indicator is that the tab on the gasket matches the little shelf on the back end of the block.

But in addition, that blown gasket appears to have 2 extra holes next to both #1 and #4, that are not in the photo of Malcolm's gasket.
Guy W

Am I completely great or what ?

I seriously doulbt this place could even exist without me

Remember... to worship me is to love me

Haha

Prop
Prop and the Blackhole Midget

Thanks for all the input, it was very helpful. Those two holes in the top of the block serve no purpose and I think they contribute to blow outs at 1 and 4. I will make sure they are dry. I am also going to go to a payen hg.
T Leach

This thread was discussed between 08/09/2015 and 17/09/2015

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