Problem idling

dennis d

dennis d

120cc
I have a 71 ct70hko that i can't get the bugs out of.I had cleaned the original carb and it would run great at top speeds(45mph),but i could'nt get it to idle.I took 3 more carbs off of other bikes and off one that ran great and it does the same thing.I have adjusted the valves also.I also have a ko model that starts first kick but only idles after warmed up.Any help would be appreciated. Thanx Dennis
 
K

K4orza

Member
Have you adjusted the pilot circuit at all (air and throttle screw)? Im not sure what the factory set adjustments are, but im sure someone could tell you.
 
M

mtkawboy

Member
I would try cleaning the pilot jet with some carb cleaner and one wire off a wire brush. The pilot jet is so small that gas over a month old is so crappy that it will clog them up. Ive fixed 2 trail 90,s this week with the same problem
 
H

Hondax

Member
Well then, I see you have eliminated carburation which basically leaves air leaks and possible a weak spark.

Valves that are excessively worn, i.e., leaky will prevent the bike from idling good. A "leak down test" is the only way I know to easily check that, but then you need a leak down tester. Often these older bikes that don't visably burn oil have compressions much less than needed for optimum performance. This can really drive you crazy.
A weak spark can affect the idle also but this is easy to diagnose. Air leaks affect idle, which is partially what worn valves do. Also make sure you have no leak where the manifold attaches to the motor. We haven't even talked about warped motor parts.....Yikes!!!
 
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M

mtkawboy

Member
Try squirting some Wd40 around the carb mounting area and see if the idle speed picks up, a sign of a vacuum leak. Have you done what I said with the pilot jet?. Its a tiny hole and plugs real easy with dead gas which takes about a month now. I always run mine dry when I shut them off
 
dennis d

dennis d

120cc
Got it solved,it was a air leak where the intake manifold bolts to the head.I never took that apart when i changed the carbs,Live and Learn.Thanx for all the help guys. Dennis
 
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