I rebuilt the carb on my sons 83 LT 125. Now the idle won't come down after I give it some gas for about 5-6 seconds. Float was set to spec, all new jets, throttle cable not sticking and in adjustment, anybody got any ideas. Mikuni VM 20 carb.

Thanks,
Gary

 

Gary,I'm no expert,but maybe I can help,If not there are some ppl in here that can.Did you check the air fuel mixture setting,I'm not sure that's the cure but it worth a try and it won't cost ya nothing.I had that problem and I did what you did,did not cure it though,now I did some reading of my repair manual and there's screen's in the petcock,atleast in an lt500,I took the petcock off the gas tank and there they were,full of crud,cleaned them out and away I went.So hope that helped....Zilla

 

Thanks for the reply Zilla. The air/fuel screw is set to spec at 1 3/4 turns out. There is no petcock on this old quad, straight from the fuel pump to the carb. I did put a small inline filter in though. One thing I forgot to mention, I've got the e-clip on the needle jet set on the 3rd position from the top, factory sets it at 2nd position but it runs too lean there and I can't keep it running. I'm wondering if the needle seat may be shot, just an idea. I've rebuilt quite a few carbs in my time but this ones got me stumped. Maybe I just need a new one, but these things are so ancient I wouldn't know where to find one.

Gary

 

Can it be that the vacuum slide is sticking in the carb with the needle way out of the main jet? The slide spring may be busted allowing this to happen. This would explain the high rpm.

Mark

 

I think markd is right...it sounds like an intake problem...check for intake leaks, also a leakdown test on the motor itself would be a great idea



BRAAAAP

 

Mark led me on the right track alright, the problem was the e clip on the needle jet slipped past the retainig clip, I replaced the retaining clip. Now this 20 year old quad runs like new!Thanks to everyone who replied.

Gary