Got an 86 Trailboss 250, she misses from about mid to full throttle. Otherwise it runs great, starts very easy, idles great, plenty of power from idle to mid throttle - then slightly misses - never gets up to full speed. Change the plug already. Took the carb apart and gave it a good bath in carb cleaner. What would you guys think the problem might be?

 

what kind of compression you got on it? May be goin bad on top end. Fuel filter been changed lately? Are you gettin good fuel flow? Is the fuel petcock filter plugged in the tank? Just some ideas of stuff to check.

 

Sounds like the reverse limiter - don't have my book handy or I would tell you how to "bypass" to verify. I'll try to remember it this evening.

 

Check the main jet. I bet its to big. That old of a quad maybe the reverse limiter.

 

Sounds like it's jetted too rich.Try a clean air filter or remove it for just a bit and see if it staightens out.

 

You need to find out what main jet you have in it. This will absoluitly make it miss from mid-top because of it being too rich. Are there any other mods done to it? Is it all stock? It is very possable that a previouse owner jetted it for winter and never changed it back. Going up 1 full size on the main in a stock machine will make it miss.

 

On those old TB's the reverse limiter is located on the front part of frame, in front of / underneath the gas tank (you should be able to get to it without tank removal), it is kind of square box looking.
There is a 2 pin plug with a green and black wire - if you disconnect the black wire going to the box, the reverse limiter will be taken out of the loop. If you decide to leave it this way, just remember that reverse will be just as fast as forward speeds.

I've seen numerous old TB's that had this problem, besides it's a lot easier to address first before tearing into the carb and rejetting.