Hey all, I am working on selling my 1990 LT250s, but it smokes for like 5 mins before stopping. I'm thinking whats happening is that the carb is washing gas past the rings, and its getting into the oil. I put my finger into the oil hole and pulled it out and it smelled like a mixture of oil and gas. Its a four-stroke so that means it takes straight gas. no mixing involved. anyways, I was just really trying to get oppinions on whats going on with my four-wheeler before i sell it. I've already had the whole engine rebuilt. had it bored .60 over and put racing valves, springs, piston, rings, etc.. into it. Hopefully I wont have to take the engine apart again. thanks, Brandon

 

I think it could be your carb. When carbs get old, they tend to once in a while to put more gas with air then they are suspost to and it burns too much gas causing white smoke. Just take your carb somewhere to get it cleaned or just clean it your self. EASY [img]i/expressions/face-icon-small-smile.gif[/img]

 

how do you clean it .. It burns a light blue smoke for like 3 mins then stops.

 

Usually rich exhaust is white. Blue is almost always excessive oil. Have you broken the engine in yet? My first guess would be that the valves aren't sealing until they heat up. I assume you had new valve seats in when the head was rebuilt?

 

I reseated both new valves with the seating compound.. I just drained the oil out totally .. havent ran it yet. Could the valves just be out of adjustment? .. They were adjusted properly i think. Could gas be leaking out of the carb and running past the rings into the oil cause it to blow blue smoke. and if the valves arent sealing until the engine gets hot, will the engine be O.K if it is ran like that, and what would I have to do to fix it ?

 

I don't think that that you'd get blue smoke from oil wash in the cylinder. How much oil came out? If you are getting that much wash out on the cylinder the new rings would likely be damaged in a short amount of time. You have a pretty short window to seat the rings well. My guesss is that it is more likely related to the valve train. Valves that leak probably wouldn't hurt the motor.

 

I reseated the valves, and they seemed to seat properly. I used the seating compound. I dont think the rings would be ruined because it would be smoking all the time, right? Do you think the intake valve is working properly, but the exhaust valve isnt opening enough and its keeping the exhaust smoke inside the cylinder? That would cause it to blow a lot of smoke on startup, correct?

 

I would assume it's the exhaust valve. Wouldn't a non sealing intake valve blow back into the carb?

 

that still doesnt tell me why its burning blue smoke. Blue indicates oil. If it were the carb, then it would be white. how do i find out where the oil is coming from, assuming its the exhaust valve

 

I understand that blue smoke is excessive oil. It is either leaking past the valve, or somewhere in the piston, maybe too large a ring end gap, wrong bore size for the type of piston, bad hone, messed up rings. Most likely it's the valve seal. I'd go ahead and pull the head off it and have the exhaust valve redone. That is if everything else looks good.