I just got a '71 A65 Lightning running after replacing the wiring harnesses. All the electrics work great, got a new battery, bike started on the third kick. But, it only runs with the choke on full. I thought I knew these Amals pretty well, I moved the needle up from top notch to middle to bottom, almost no difference. I have the idle screws out 1.1/4 turns. As soon as the choke is pulled up beyond the slide, it dies. It has new main jets and needles, 200 mains and the needles have the two lines on top.
Check for air leaks at the carb and the inlet balance pipe. With the bike running spray some carb cleaner or WD40 (even easy start if you have it) at the point where the carb meets the head. WD40 will cause he engine to stumble, easy start or carb cleaner will cause the revs to pick up momenterally.
If thereâ€™s no leak then nothing should happen.
Needle position and main jets have little to no effect at idle.
The only effective way to clean the pilot jets is with a #78 drill. solvents and air wont do.
You do know that choke is off with a tight wire, so it is most likely the pilot jets or the pilot jet delivery holes in the venturi are blocked.
Yes. If the pilot is blocked it will have an effect well beyond idle. The pilot circuit provides base line fuel for a wider part of the amalâ€™s operation than just idle.
Choking the carb reduces air flow so more fuel is ingested. Ergo, you have a shortage of fuel before the choke slide( or an excess of air after the choke slide).
Both posts above are on the money.
as a temporary solution the pilot jets can be poked clear with a 0.016 "guitar string , B, , however this moves the dirt back into the fuel passage , it will probably re block at some time, the # 78 drill removes the dirt when spun in the fingers, Google" Amal pilot jet cleaning #78 drill", to see the full method.
Don't forget to clean those 2 tiny holes under a slide and check the mixture / air has unblocked pathway from mixing chamber to them, without it cleaning only pilot jet won't be enough.
You might find #78 bits at a hobby store. Easy enough to order a bunch from the interweb.
When you get one push it into one of those tubes that come with carb cleaner or WD40 and secure it with epoxy.
Thanks for all this, bought #78 bits and will check all these soon as the work week lets up.
be gentle, they are no fun to remove when they break
Follow-up - the drill thing worked, took 'em apart, reamed out all the passages I could find and blew 'em clear, runs like a champ now. Thanks for all the feedback.