I've put a new kit into this Amal 620. Got prelim idle set, got it up to op temp and the air mixture screw at 1 and 3/8 turns. Trying to fine tune this machine and the air screw has no effect on tuning at all. Does not run terrible as is.
Reviewed the carb and seems is it assembled correctly. I cannot determine if the carb has been modified or damaged.
Any guesses on my situation here?
Hi,
Is the carb only a 20mm as the A50 has a 26mm specified. The ineffective air screw could indicate a blockage in the jet. Carb cleaner and air line may clear it.
What revs needed to get it to 'idle'?
Dave.
Check the mixture screw hole hasnt gone tapered with years of use.
The slide screw is possibly lifting the slide too far above where the idle mixture has any effect. But more likely would be the little mixing chamber (that silver disc in the carb body) is blocked up, as would be the transfer holes into the carb.
If yours is the original carb with screw in pilot jet, do your self a huge favour and buy a new premier carb. Amal carbs, especially concentrics are considered consumable items. They weren't meant to still work well after nearly 60 years.