question about an older motorcycle

Question Description

I’m stuck on a question and need an explanation.

I just got a 1981 Honda xl 500 and it wont rev out when we rev it up all the way it crackles and boggs out but when we suck on one of the hoses itll rev out with no problem what could be causing this?

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Final Answer

The main jet was way too rich. We`d already done the basics: clean filter, new plug, valve lash adjustment, cleaned the carb with compressed air/carb cleaner and set the float height.

Amazingly enough the main jet on this bike interchanges with just about any Keihin motorcycle carb made around this time (70`s and 80`s)...maybe even later model Keihin carbs. I took a #115 main out of a spare set of carbs I bought for my old CB750 and tried it just for the hell of it and it threaded right in. Bike is definately too lean now (pops on decelaration) but revs out nicely and pulls like a raped ape. We ordered a bunch of main jets to try in the bike from #125 - #150 so we will get it dialed in correctly for sure.


Smartbrains (326)
Boston College

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