OK first off, this question is about my LT250r. I figure I would ask it in here since a lot more of us Polaris owners have a 2 stroke, and know a lot about jetting. On a freshly built motor with new everything, and a squeaky clean carb, it starts and idles great. From idle to a little over half throttle it runs great, and seems it could run all day that way. But as soon as I open it up, it seems to start to bog a sputter, is I keep it there for about 3 seconds, it will die and not start. I must clean the plug to get the spark back.

The plug looks almost fine, just a little wet, and looks to be the typical oil burn that is on a two stroke, but nothign exseccive. My Polaris has ran with a much worst looking plug. I even went to a hotter plug, and that changed nothing. The only thing I know is the Main jet controls the upper part of the jetting, but I shouldn't be fouling out that fast even though it may be a little rich. (Stock carb and jetting by the way) The only things that I've done to the motor is an FMF pipe and silencer, FMF Ram Valve, K&N open box, and a .010 over Wiseco. Any ideas????

 

maybe your mainjet vibrated loose?

 

Is your filter clean and did you ever figure out the problem?

http://justkdx.dirtrider.net/printcarbtuning.html

 

Hey FN Sport
You say a squeaky clean carb... may be while cleaning the float you bent the tang one way or the other. Did you measure the float level for whatever the specification is for the carb? Its gotta be something simple thats being missed.
Was the FMF pipe, Ram Valve and K & N filter on it before the rebuild? I really dont think the stock jetting would work 100% with those mods. Get in touch with FMF cause I think you have to increase your jet size with that pipe and filter modification. More air and better breathing means bigger jets, what size I could'nt tell you.
Good luck its in the carb.( Unbiased and Non-Professional Opinion ).....DUG

 

Measure the float level.If that doesn't do it lean it out a little with clip position.Also,while you're there make sure the rubber on the float needle isn't hard that will do it too.

 

thats weird that with stock jetting and those mods its running rich! you would think it would lean right out..
i dont know much bout jetting so i dont know..

 

Well since you say that you pull the plug out wet, I would have to assume that you are getting the fuel you need. I would double check your K&N air filter. Even if it doesn't look dirty, wash it out really well. If it runs good till half throttle then bogs, you are most likely not getting any air if you are pulling out a wet plug. Good luck in finding the lost horsepower!!