A few weeks ago I was riding with some friends at the dunes and they were saying my 440 was blowing white smoke at full throttle and when I let off the gas, I thaught they were full of **** until I looked at it today and it actually was doing that. What could be wrong with it? I just installed a new piston and had it bored but it was doing it before that too. My other 440EX motor did the same thing, even after I replaced the valve seals, what in the hell is wrong with this thing?

 

piston rings might be bad, or it could be running rich, but when its rich its usually darker smoke i think

 

i think this is somewhat normal for the 400ex's. they all seem to use a little oil when ran really hard. when i made the switch to mobil 1 15w-50, the problem greatly diminished.

 

it's running a little rich yes but thats not the cause of the smoke, this is definitly oil burning smoke. the rings and bore are brand new so that cant be it. I might try running 20w 50 but im not sure if that would be such a good idea as it may cause my clutch to slip. I used to run 20w 50 last summer with my old motor but that was because it knocked and smoked but I dont think the clutch slipped, I'll try running it again and see if that solves my problem. thanks for the help.

 

Now what did i tell you?????? Damn right it does burn oil... looks like your full of **** this time bud[img]i/expressions/face-icon-small-wink.gif[/img]

 

i dont know alot about atv motors but when you rebuild a car motor depending on the type of rings you put in it might take some time for the rings to seat.

 

i don't have any clutch problems with full synthetic mobil 1 15w-50. i do believe the other oils offered by mobil 1 are certified and aren't recommended for wet clutches.