question about an older motorcycle

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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?

Sep 11th, 2013
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.

Source
http://www.dirtrider.net/forums3/showthread.php?t=121267
Sep 11th, 2013

whenever you suck on that hose though im guessing your taking air out of the carb and it runs just fine so it could be the air intake but we cant find a way to adjust that and we gotta check the valve now cause it might have a hole in it and need replaced

 

Sep 11th, 2013

found out the problem was the seat was wrapped in ducttape and being sucked down into the air box blocking off airflow we cut the tape off and now its running great was such a simple problem we felt so stupid wasted a week trying to figure it out

Sep 20th, 2013

That sounds great!! Sometimes a small problem makes you worry so much but I am glad you were able to figure out the problem and rectify it on time.

Sep 20th, 2013

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Sep 11th, 2013
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Sep 11th, 2013
Dec 10th, 2016
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