I just bought a DVX 400 two weeks ago and was eager to get it broke in, so I took it to the club that I belong to and rode it lightly on the motorcross track for a couple days until it was ready for the first break-in tune-up. I took it to my quad mechanic and handed it over to him with a UNI air filter that I purchased last week. He completed the tune-up (nothing worng with her) and oiled and installed the UNI for me. He said that I shouldn't have to rejet with the filter, but if it cut out at high reving, then maybe I would need to do something to it. Well, I rode it yesterday and rode it for about 10 minutes total before it died on me. When I wrapped the throttle in any gear, it would stall for a second and then have a good amount of power. It did this until it finally just stopped working all together. Now it is turning over but nothing happens. Could there have been too much oil on the filter, making it run rich? COuld it have been running to lean with the new filter? Is the problem a spark plug issue at all? Any help would be greatly appreciated!
Thanks

 

When they stumble like that it is usually means the emgine is to lean, what color is the tip of the spark plug? If it is white or has metal on it you may have damaged the piston. If there is metal on the spark plug you melted the top of the piston. Was the engine frozen at first, then when it cooled down would turn over? If so you surely stuck the piston and probaly have metal on the plug. Change the plug and if it starts, you burnt up your motor. Any intake or exhaust change needs to be checked for leaning the motor out, always and everytime regardless of what anybody thinks or says. It get expensive it you don't.