high rpm

[spink813]

I have a 1980 xs400 special . Runs and idles good seems to drive well also. Heres my problem sometimes when you twist throttle it takes a longer than normal amount of time for it to return to idle. Give it a quick twist and seems like still holding throttle but cable has def fully returned. Any help would be great thanks.

 

[motoTrooper]

I think your situation is called a 'hanging idle' due to a 'rich' fuel/air mixture. I believe turning the air screws (located on top of the carbs on the filter side) out a half turn or so will settle it down. I am just getting into my own carb adjustments on mine so perhaps someone else will have a better take.

 

[CDNTX650]

hanging idle is usually "lean" from either, air leaks, or modified exhaust or intake. It can also be cause by a sticky timing advance or worn out return springs.

Signs of rich idle are idle that hunts a bit, or dips below set point with small throttle blips.

 

[xschris]

Carbs out of sync or carbs with a bad diaphragm will do this also.