Engine Revving Issue After Rebuild – Possible Auto Advance Problem?

[7iain7]

Before rebuilding the engine, I had an issue where the revs would either hang or drop very slowly. At the time, I tried fitting a Chinese copy of a Mikuni carb to see if it would help.

Fast forward to today: I’ve rebuilt the engine and installed a brand new Wassell carb. The engine starts up fine and idles beautifully. However, when I give it some throttle, the revs hang at a high RPM and only slowly return to idle. The slide in the carb is fully closing, and the throttle snaps back as it should.
Also there does not seem to be any obvious air leak.

Given that the carb seems to be functioning correctly, I’m starting to wonder if the problem lies with the automatic advance unit. Has anyone experienced something similar or have any insight?

[muskrat]

G'day Iain.
Sounds like an air leak or lean mixture to me. With the motor warmed up and running spray copious amounts of WD or similar around the carb flange and top of carb where the cables go in. If 100% sure of no air leaks and the plugs look a good colour move on to the timing. Eliminate the easy things first.
Cheers 

[KiwiGF]

Has the Wassel carb got a choke cable arrangement and if so either is it blocked off or a cable fitted? I recently encountered a guy who was having issues with his bike running lean and overheating, and his new amal did not have the choke cable fitted hence air could get in, solved by taping it up until he could fix it properly.

Before rebuilding the engine, I had an issue where the revs would either hang or drop very slowly. At the time, I tried fitting a Chinese copy of a Mikuni carb to see if it would help.

Fast forward to today: I’ve rebuilt the engine and installed a brand new Wassell carb. The engine starts up fine and idles beautifully. However, when I give it some throttle, the revs hang at a high RPM and only slowly return to idle. The slide in the carb is fully closing, and the throttle snaps back as it should.
Also there does not seem to be any obvious air leak.

Given that the carb seems to be functioning correctly, I’m starting to wonder if the problem lies with the automatic advance unit. Has anyone experienced something similar or have any insight?

[berger]

i put a small fag filter in my choke cable fastener works a treat on betsy and betsy 2

[BagONails]

Kiwi, I literally just saw a video from Paul Henshaw where he mentions this and shows us a great idea to cap off the redundant cable abutment.  He uses a plastic valve cap, fits perfectly apparently. I can't find it now unfortunately but you get the idea.  Pretty sure it was an Amal but the Wassell carby's are pretty well a carbon copy and share all the same parts I believe.