My 400ex smokes blue when i let off the throttle and then punch it again hard, what could this be? i think i might be burning oil, and how do i fix it??

 

i no from my zippers(2strokes) a lean fuel mixture will do that. but dont no if your quad is a 2 stroke. if a 4 most likely oil.

 

but what do i do to fix it?

 

if its burning oil your gona need some piston rings

 

First determine for sure how much oil it is burning. If using too much oil then you need a full top end including bore, piston, rings, and more than likely valve work and valve guides. Make sure you check the oil level after getting the motor up to full operating temp and then shutting off and don't screw the dip stick into the stick threads but just sit on top of threads.

 

almost all sport quads smoke when they are first started. once they warm up it goes away. this is due to the piston needing time to warm up and expand. if it goes away after 5 mins or so i wouldnt worry about it. if it is a constant problem i would say its bad rings. especially if its a stock bore. have it bored get a new piston, rings, wrist pin, and bearing, and dont skimp there. you really get what you pay for. while you got it apart go for an 11:1 comp piston for a little extra power.

 

when you let off the throttle at high rpm and let the engine braking slow you down and smokes when you punch it again, it's worn valve seals and/or guides. the vacuum in the intake manifold from the engine braking sucks the oil down the intake valve sem into the intake, and when you punch it, the air that comes back in picks up the oil and pulls it into the combustion chamber. I'm 100% positive that's what it is. I'm an auto technician, i've seen it hundreds of times.

probably not a big deal if you dont have the money, a little oil wont hurt too much i dont think. just make sure you oil level stays full. You probably DO NOT need piston rings if that's what it is, despite what the other posts say, but that is just my 2 cents based on what you said.

 

yah, it sounds like quick has it right on, how much would it cost to fix this?

 

its real cheap and easy if you have a service manuel, some basic hand tools and some slight mechanical knoladage........the guides are around 15 bucks and the seales are 7