For the past few months this thing would smoke a bit w/ higher rpm's. After upending it to retap the drain plug hole, the carb was dirty, ran a small amount of Sea Foam directly through the carb and seemed to clean it out good enough. I then poured about 1/2 the bottle in the gas tank, on the way out for the weekend it topped of the tank w/ 93 octane. For the first 30 min or so, that thing smoked like crazy! Guess that's a good thing. Now the valves are knocking again, guess it cleaned up the valves a bit, I'll re adjust them later.
Question is why does it smoke after it sets for a while, and then clear up after a few mins of riding? I'm probably still burning some sea foam, but I thought it was odd that it didn't smoke continuously. After about 2 hrs of riding, the exhaust was clean and dry. What causes it to burn oil? Why does it seem to stop after the eng warms up? Any quick fixes?

 

maybe runnin rich..makin your plug dirty.. when 1st started it burns the gunk off. what color ish tha smoke??

Old rings maker smoke..valve guide seals maker smoke

 

Most likely the valve guides/seals are worn. While it sits, the remaining oil on the valve gear drains down the stems and ends up in the combustion chamber. You start it cold, and it burns off , but after it burns off, the leakage isnt that great, to make smoke once its running.
There really isnt a quick fix, and if the performance is still ok, id just keep an eye on the spark plug, and if it starts to oil foul, go to a hotter plug, and just drive it.
You could do a compression test, and see how far the compression is down, but if it starts and runs, it cant be too bad.

 

it is good to smoke at first start up, but not if you been riding for a while and engine is already hot and still smoking !
it just the rings are cold (not warm) and little oil slips by and burns up, after they warm up the rings tighten and seal up and the smoking goes way. could also be valve/guides seal as hondabuster said!

 

I just purchased a used 95 foreman 400 and when I loaded it, unloaded it and ran about 100 feet I did not notice any smoke, pulled it in the shop, looked everything over and poured about 1/4-1/2 can seafoam in gas tank and all of a sudden I have white smoke and smells like oil. Can the rings or seals be bad or is the seafoam causing the smoke. I use it on vehicles and when it gets sucked in thru a vacuum line the vehicle will smoke like a tar pit. The 4 wheeler was advertised as good shape and it was raining like a dog when I picked it up and I will be pi??ed if it needs a top end. I do know it needs a valve adjustment.
Thanks,