I have a 1986 LT 125 that is in great condition that I'm having some minor running issues with.

The problem is very inconsistent, no pattern really except for when its cold. Basically, it runs at its best when its cold. It'll really wind up in high RPM's and has a lot of "get up and go". Then out of nowhere, it'll seem to bog down and lose power. Sometimes while driving down the road it'll all of the sudden get a surge of power and take off but then minutes later bog down again.

I recently tore the carb apart and re-built the carb. I've tried adjusting the needle, adjusting the air/fuel mixture, new spark plug and air filter all with no luck.

Please help!

 

Well...given the symptoms you described I'd check:


1) Make sure the gas tank vent line is not being partially obstructed


2) overheating? - when an air cooled thumper gets too hot they loose power...but I wouldn't think that would be the issue (unless your cooling fins are all caked up with crud)


3) electrical - this is the tough one, but electronics do funny things when hot or if connections start going bad...take a good look at them all and apply dielectric grease after inspection/cleaning

 

As far as the electrical, any specific connection/system that I need to focus on?

Thanks!

 

Well...I'd start by yanking the plastics and inspect all you can see (lets face it...it's 30 years old now)...hopefully you find something obvious. Otherwise you might need a manual and ohms meter to start test resistance on the more critical items...


I'm also reading that you have a fuel pump that is vacuum operated...that might be another item to look at if true...check the hoses for cracks and the fuel filter/connections...


If I were you...the next time it bogs...I'd shut it down immediately and see how much fuel is in the bowl...if full, then I'm back to electrical, if not full, then it's a fuel delivery issue...