Need help with SU needles and rolling road tuning places.

saitrix

saitrix

saitrix

Soldato
Joined
2 Jun 2003
Posts
8,950
Location
Nottingham
Hi,

I had my Dolomite rolling roaded tuned which I found that my AFR is out on it. So he had to slacken the timings on my cam. As you can guess I would like to get the correct needles for it, I am already running the richest of the 3 needles the Sprint came with, 0.1" BBT needles. The AFR shows up it is running lean at all revs, especially higher up, except at 2500rpm which is it about correct.

I have tried contacting Burlen but they said they arn't able to help me on what needles I need to swap to, and the rolling road place I went didn't keep stock in of needles so couldn't try different ones.

Does anyone know of places I could go for a rolling road tune, or know how to work out what needles to use? Anyone have WinSU by anychance? Really I am after any help on this one.
 
It's a bit of a bodge, but you can actually file a flat onto the needles to richen up the mixture. One of the local rolling road operators was infamous for this :D Of course knowing where to file and how much to take off is the difficult bit...

WinSU is only a tenner to register, and the free version is still useful for comparing different needles.
 
Dogbreath said:
It's a bit of a bodge, but you can actually file a flat onto the needles to richen up the mixture. One of the local rolling road operators was infamous for this :D Of course knowing where to file and how much to take off is the difficult bit...
Click to expand...

No way is that a bodge, its a well known method for perfecting your fuel mixture because no standard SU needle is perfect for your engine. To be honest Satrix, i would just use the WinSU program too find a needle, i did for my mini and it seems to go pretty well.
 
[huzeeee];10972938 said:
No way is that a bodge, its a well known method for perfecting your fuel mixture because no standard SU needle is perfect for your engine.
Click to expand...

It is a bit of a bodge as you tend to get poorer fuel atomisation, which was never a strong point of the SU anyway. It's worse on the HIF carbs where the needle is free to turn, so the flat could be behind, to the side or in front of the needle, and as the needle is biased it can cause excessive wear to the main jet. A better option is to thin the needles using (idealy) a watchmakers lathe, or for DIY sticking it in a drill and using a fine file to machine down the needle. This also means you can quite easily get a matched pair of needles by using a vernier calliper to measure the diameter, and you can then match your modified needle against a proper one using e.g. WinSU.

BTW, no carbs give you perfect fueling, that's why fuel injection was invented :D
 
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