[spottie]

Can anyone tell me what the idle jet size should be for a 33 1.7QV running 40IDF carbs? Cheers John.

 

[evilgidget]

Idle jets - 50
Main jets - 140

 

[spottie]

Just checked

the carb, it's running a 50 idle, 140 main, 200 air correction.

 

[spottie]

Idle jet size

Should I go to 55's on the idle jet, or 52's as the next step up from the 50's?
Some Weber sites only carry the 55 as the next step up, but I noticed that 52 is available as well.
The reason I am changing is because I can't get the adjustable fuel mixture jet to run at the 2 1/2 turns out, it won't run at less than 3 1/2 turns. The Weber help sites suggest increasing the idle jet, but how far?.

 

[77SudTi]

I feel your pain. I have never got my idle circuit to run well with the 2 1/2 turns out, mine is more like you said at 3 1/2 turns actually more like 4. I thought it was just me, but good to know someone else has the same issue.
Has anyone got an idea as to why this may be?

 

[spottie]

Idle jets to small

cause this apparently. By richening the needle this compensates for the lean idle jet, but this also makes you have to increase the idle stop to make it idle at anything like the right speed. So fuel consumption suffers as you are running a slightly open throttle over what would normally be the case. Also the engine hesitates just above idle speed on take off as it overcomes the leaness, or something like that. Of course I stand to be corrected.

 

[77SudTi]

yup, I get the stutter just off idle too, all I can do is shift it up and down the revs, right now its at 2000rpm as I tried closing the plug gap a bit which I read somewhere may help, it seriously drives me nuts!!! I have been trying for so long to get a smooth running engine, but I can only get about 97% there!
A lean idle jetting would help to explain this...let me know what happens if you go about changing yours.