Hey fellas I’m looking for some help I was handed down a bear tracker 250 from my father and I have had some issues that are mostly fixed but I have a reoccurring problem with what I’m guessing is the carburetor. When I crank the four wheeler it will start up perfect BUT I cannot rev it until it warms up 4-5 mins later sometimes longer. I’ve been told in the past to put a fuel filter on after I finished rebuilding the carburetor which actually seemed to improve the problem a bit. I have also noticed I cannot pull the choke out at all or it will die. So I believe that it is to rich. Would anyone know what I need to do to fix issue I am having.

 

Check your inlet manifold for cracks and that the flange seals are OK. Not being able to rev up is a sign of a weak mixture, stalling if you try to use choke is a sign of a rich mixture, so the opposite. May be an idea to look at the plug nose colour after it has been idling for those few minutes, black and sooty = rich, white and clean = weak. I would clean out the carb again, and double check you got every part the right way the first time you rebuilt it. So easy to put something in upside down or back in the wrong order. These days, it is often easiest to just buy a Chinese Cheapo carb and hope it is set right to be "plug and play" but sometimes they give problems too.

 

So it’s definitely a rich mixture the plug was black after idle. I can rev after letting it sits for a few minutes. I rode it around everything seems to work after warming it up. Could it be possible that I’m flooding the engine?

Also I replaced the inlet manifold a while ago due to it having a huge crack in it. I bought a Oem inlet off partzilla to replace it

 

Seems strange it runs better when warm as a rich mixture causes worse running when hot, If you leave the choke on with a correctly set bike, it will start to run badly as the engine warms. Some sort of strange electrical problem is just possible, though again, failing coils usually cause worse running when warm. Try a fresh plug, even if the one now fitted is newish. A new plug doesn't automatically mean a good plug.

 

I've had issues with a 2003 Yamaha Wolverine where the parking brake sensor makes it unable to rev up. It sounds like it is bouncing off the throttle like a rev limiter, I just shook around the parking brake and it worked. I don't know if that is your problem but it is worth a try.