Series ‘A’ Twin Carburetion

[greg brillus]

I'm not sure how that relates to a pre war twin issue, but if that is the case, it is enriching the mixture by leaning the bike. If the idle speed is too fast you will need to adjust both the mixture and idle speeds to get it lower. Apart from a sticking ATD the issue with a bike that idles too fast once you back off the throttle can be that the idle mixture is too lean. Best to set up on a warm not hot engine, if necessary run a fan across the engine so it does not get too hot, and make adjustment quickly. It is a lot of "Back and forth" until you get a result. The issue we are having with the new "A"'s is that we have no reference to go off, as none of the bikes are running original carb's.

 

[billirwinnz]

Hi Bruce

Leaning your bike is raising the float level and richening the idle mixture. Screwing the pilot screw in a little (to reduce air flow) will have the same effect. With the bike level and hot, adjust the air screw for maximum idle speed and then screw it in just a little to give a slightly slower and more reliable idle. Adjust the slide stop to set the correct idle speed. You may need to repeat this a few times as the two adjustments interact. On a twin I remove one plug at a time and adjust each for a slow reliable idle. When both plugs are firing the idle speed increases and I back off both slide stops equally to obtain the right speed. You should first have made sure that both slides have cable slack and lift simultaneously.

Cheers Bill