Carburetor Black smoke

[Iron Andy]

Hi all,

took my bike out for a test ride to check the new clutch I'd just fitted.

When the bike is stood ticking over there is black smoke coming out of both exhausts. Bendix carb fitted, the pilot screw is 1 & 1/2 turns out from being seated. There is also an adj. jet.

I have set this to the same position as it was before I cleaned the carb. How does this adj. jet affect the performance of the carb?

My bike is not legal so it's a little difficult to take out for long test rides as I live in the middle of a city.

Many thanks,

Andy.

[the_french_owl]

Hi Andy,

Iddle a bit rich most likely.

Set the throttle stop screw to get about 1500rpm with throttle closed, warm engine. Then slowly screw in iddle screw until engine start to miss out (1/16th turn at a time and let engine settle). Back off about 1/8th turn. Readjust throttle to bring iddle down to 1000 rpm. redo a few times and test on the road. Best iddle screw/throttle stop screw compromise is when you can accelerate sharply without any hicups from the engine.

Always leave the iddle screw ever so slightly rich, it helps starting. Don't aim for too low iddle revs. If difficulty in starting, too lean an iddle. As a rule, iddle screw is around one turn out from seated when set proper.

Patrick