Hi, i have a 1999 Kawaski praire 400. I rebuilt the top end of the engine for a school project, we put a new piston, rings, camshaft, and new valves and lapped them in so it basically has a fresh top end. Once we got it running i went out and drove it around for a little while and when i came back into the shop there was mixutre of oil and gas leaking out of the bottom of the air box. We looked around and found a vent that comes from the crankcase that vents into air box and thats where we think the oil is coming from cause there is air pushing out of that vent.
Would this all have to do with the carburation? cause the four wheeler only runs good when it is on choke. we took the carborator off about three times to clean it and most of the jets were all plugged. If not the carborator what else would be causing the crankcase pressure and blowing the oil out?

 

Welcome to the forum!If you have mixture of oil and gas in the air box it's usually carb related flooding the crank case. Probably the needle and seat if you haven't replaced it or the float level.If the engine only runs good with the choke on sounds like you need to go back through the carb and check it out,plus blow out the jets to where you can see through them! Not a bad idea to change the oil if it smells like gas also! OPT

 

Ya we havent replaced any of the jets or anything in the carborator yet, we cleaned it twice and blew out the jets. The four wheeler sat about four or five years with gas in it and the carb was pretty gummed up. I think i am going to order a carboartor rebuild kit and try putting that in it and hopefully that will help solve the problem.