Help! big motor problems with 02 400EX

[DaddiosRacin111]

I was riding my quad this winter and I noticed the vlaves were ticking rather loudly. I put my head down next to the motor and cranked it to 3/4 throttle to listen to the motor. Then it went way high up in the rpms and shut off. All the way down through the rpms while I was rolling to a stop, it sounded like I broke the connecting rod because something was slapping around in the motor. I waited 15 minutes and went back outside and it started right back up but it burned oil really bad. I mean like 2 cycle bad. It smokes worse than my 2 cycle 250. It will empty the oil tank if you ride for 2 hours it burns so much. The valve are also making a ton of slapping noise now. I tried to adjust the valve clearance but it did nothing. Does any one have any idea what happened?

[bigkahoonaburger]

Unlike a 2 stroke, in a 4 stroke, oil is really not supposed to be able to get around the piston rings to be burnt. as far as the valves clattering a lot i have had experience with the piston being so worn down on the sides that they started to make what is called piston slap. and in my case, the longer i ran the bike the louder the noise that i thought was valve clatter got. it was not valve clatter, it was a severely loosend piston in the cylinder wich caused it to flop around (piston slap). it also burnt more and more oil and became harder and harder to start due to low compression.
I don't know if this is what is happening to your 400 but i had to have mine bored and put a new piston. I have also heard that if you got the quad hot enough the lower rod bearing on the crankshaft will go bad due to extreme heat so be careful if this is actually the problem and you decide to do the engine work yourself.
Good luck.