CARRY ON CARBS
Robert Allsop has just fitted new Wassell ‘Evolution’ Concentric-type carbs to his ’72 Bonnie. It now ticks over nicely and runs well, but he says: “With the throttle just off the stop when pulling away, the engine gets very lumpy and the plugs are sooty. Is it worth trying a smaller needle jet or is it something else?”
Well I’d say we’re back to last month’s suggestion of marking the throttle grip so you can see exactly where the problem occurs. As you open the throttle, the slide cutaway first comes into play followed by the fit of the needle in the jet. Pulling away usually takes more than ‘just off the stop’, so it would be worth finding out exactly where the trouble occurs. Then you can work out the most likely setting. I’d try dropping the needle by one notch first. Then maybe try the smaller needle jets, saving the weaker slides till last. Slides are numbered with their cutaways; the higher the number the weaker the slide so a 3½ might be better than a 3.