I need a little help i have a 91 polaris 250 trailboss 4x4 i just got a couple weeks ago it floods out after running just a few minutes plug keeps fouling and has lots of spark i started to pull the carb and when i opened the air filter it had fuel sitting in it and every time i crank it over gas runs in the filter housing so i pulled the carb the needle and seat seal float level is good does anyone have any ideas.
Thanks for the help

 

Welcome to the forum! If you're SURE the carb isn't the problem(needle and seat have been replaced,float level ok) then do a compression check. If it's around a 100 pounds compression or less,this could be the reason. Wouldn't be able to take the fuel and would just flood the engine and back into the carb. You can try to drain the crank case(10 mm bolt at the bottom of the engine) to remove any gas in case the crank is flooded. Then try to crank with the throttle wide open which would force the rest of the fuel out. Have had a bunch of em brought in in flooded conditions. Also worn crank seals could be the problem by not compressing the fuel mixture and leaking air. You may need to check into at least a top end rebuild and crank seals if compression is the problem. You would be taking a chance on just a partial rebuild though on a 21 year old atv. OPT

 

Thanks old polaris tech
I will check that today i did have another problem with it when i first got it i didn't think to mention because i just figured it was from the flooding the starter was full of oil, is there a seal on the crank that would allow that under normal running that maybe bad as well?

 

Starter can get full of gas/oil because of bad crank seal behind the stator plate.Also the crank seal behind the drive clutch is prone to usually go out first,but on a 20 + year old machine anything can happen. When you get this atv running(after what needs to be repaired) always turn the fuel valve off when not in use. Saves from having the carb dump a load of gas into the crank case destroying seals. OPT

 

well you hit the nail on the head only has 92 psi comp after pulling the head and seen how bad that cylinder was worn i cant believe it was able to run at all I guess its time to rebuild it

 

Be sure to check the rod for any up and down play(side to side play ok) plus any crank bearing roughness or noise as you turn the crank over after you pull the top end! After 21 years wouldn't trust just a top end rebuild only! Worn bottom end can take out a new top end if it starts spitting bearings either from the crank or rod,etc. Have seen good money go down the drain when people have done this. OPT

 

Thanks for the info i figured as old as it is and lack of repairs on it that i should go through the whole thing and replace all the bearing and seals along with a new top end

 

Best to take the crank and have a new rod kit installed,plus you have to have a bearing separator and heat to remove the oil pump drive gear to get to the magneto side bearing on the crank! Best to let a machine shop do this and true the crank up. Check prices on rod kits,about the cheapest I've found and used quite a bit was Hot Rods. Any good machine shop or dealership should be able to use your rod kit and do it for you. Good luck OPT

 

Thank you very much for all the info

 

old polaris tech

I want to write and thank you once again i finally got time to get that trailboss together after rebuilding the motor you were right that thing runs great now. I do have one more question for you that you or someone else may have the answer to i have gotten a 2000 polaris scrambler 500 that i need to find a break down for the carb someone has had it apart and either it was put together wrong or there are some parts missing it doesnt look right i have rebuilt many carbs but this one doesnt look right inside

Thanks Riccoman