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MG Midget and Sprite Technical - New V3 carb needles

I know Laurent from France has asked this question before, but I donīt think he got any answers. So I try again:

I am rebuilding a pair of original, very little worn SU HS2s for my Mk 1 midget. The new spindles are a really tight fit in the carburetter body. Nice!

I thought it was a good idea to replace the original V3 needles, just as a rebuild routine. But just like Laurent, I notice that the new V3 needles are at least 5 mm shorter than the originals. Why?

I also notice that the new, blue dashpot damper springs are quite a bit shorter than the originals, with fewer coils.

I am now inclined to re-use the old parts. What would you do?

Tore
Tore

5mm...Gez, (I mean JEES...LOL)

Ive heard of fileing the tip of the needle to make the carb run more rich, but 5mm thats just hairy

Im JUST purly guessing, and most likely wrong... but here is my 2 cents worth

My thinking for a really short needle and shorter spring is to make the carberation much more responsive, No doulbt the needle has been completely re-profiled so the needle and piston dont have to move as much up and down to create a richer running carb...with a shorter spring the piston can move further up the range thus giving more air. intresting thought, but Id have to think that the wear on the needle and jet esp. in the mid range would have to be substancial at best.

An Idea I have been kicking around for the past 6 months to accomplish the samething which I have never heard of anyone mentioning before, so probably wont work is this....

Agian this is on a HS4 so not sure if the HS2 has the same thing but Im asumming it does....but on the carb piston there are 2 holes in the center of the piston these 2 holes run vertical, and ("Help") to determine the amount of ease of rise and fall of the piston ("along with the spring and oil"), Put blocking those holes severly limits how fast the pistons rise and fall inside the dashpots, my guess is by "EN-LARGING those 2 holes and filing the tip of the needle off for richer A/F ratio along with a cutting down the dash pot spring and REducing the vent hole diameter on top of the fuel bowl a small amount would make the carb much more responsive, meaning the fuel is much more imediate with alittle more force going into the intake...then agian you could probably get a fuel regulator and bump up the fuel pump pressure and shoot for the top end of the 2-5 psi....granted you dont want to pump the fuel PSI beyound the top end of the 5 PSi, but hey why not shoot for a the higher end instead of settle with the lower end.

Agin this is just My personal idea, and in no way should be considard a workable nor easy modifcation, it probably wont even work and even then the math involved is going to be astounding, because this mod will utilise extremely small filing/metering adjustments...but something I want to play with (way down the road) agian, Id only do try this on junk carbs 1st

Prop
Prop

As to what you should do aka...try the new V3 carb needles or/VS. stay with the standard tried and true set up???

I think that depends on why you drive a midget!

If you want a good running midget, and hate the constant fiddling, and perfer gas,oil, and drive midget ownership instead of constant fiddling, always thinking about your next modification, then Id say stay with the tried and true standard set-up, and wait 30,xxx miles when agian you need a new set of needles.....then look at the V3 needles agian to see how they faired

But If you have that "I wonder how it works inside" mentality, and enjoy seeing the hood in the open position more then you do driving, then yeah definatly try the V3 needles.

Prop
Prop

Hmmm... Very complex theory, Prop. I will have to think about it. But these carbs will be rebuilt to standard spec, just like the rest of this car.

I have a dream that may be once I will get a second Spridget and do a lot of modifications to it. Then I will first have to sell the very sad and rusty MGA coupe project I have in a barn...

Tore
Tore

Tore-As long as the needle isn't completely out of the jet when the piston is at maximum lift, I don't think the shorter length is a problem. Also, the spring wire size and number of coils shouldn't matter as long as it produces the same weight as the spec. To put your mind at rest, you might try contacting Burlen Fuel, as they probably produced the items.
Berry Price
BTP Price

This thread was discussed on 04/05/2009

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