I have a 1990 Polaris Trail Boss 250cc Two Stroke 4x4 that has the following issue. After starting up it will idle fine and run fine for a few minutes, then it will backfire while riding it. This usually occurs when going down a hill. After which, the engine will bog down and stall out. It will then not start again until it cools off. I know that the previous owner had some work done to it. I think that he had the top end rebuilt and had a new piston installed. Does anyone have any suggestions as to what may be wrong and how I can fix it?? Thanks in advance for any help that anyone can provide.

 

May have had top end as you said BUT if bogging down and dies,wont start until cool sounds like loosing compression when hot, could be that,crank seal leakage(usually erratic idle and dies) COULD BE just carb problem also if only boggs going down hills,could be loading up with fuel? CHECK compression first,should be at least 100' minimum,if ok,check carb and air filter,check/replace plug. Backfiring could be compression related,fuel or even elecrical! Process of elimination,you will probably find problem fairly easy! Good luck

 

sounds to me like it has a leaky exhaust valve.or burnt, pull the pipe off for inspection.with valve closed use solvent or gas to determine if the valves is seated properly.try that

 

<div class="FTQUOTE"><begin quote>Originally posted by: ricishear

sounds to me like it has a leaky exhaust valve.or burnt, pull the pipe off for inspection.with valve closed use solvent or gas to determine if the valves is seated properly.try that</end quote></div>

[img]i/expressions/face-icon-small-happy.gif[/img] 250 traiboss is a 2-stroke,no valves. At least none that I've ever seen,maybe hiding from me! Have a good day!

 

LOL. Valves in a 2-smoke 250. [img]i/expressions/face-icon-small-smile.gif[/img] Where have they been hiding them all these years?