Vanginkel
06-02-2011, 07:24 PM
Hi guys, just bought a 2004 YFZ 450. Bike won't start, the timing is right on, set the bike at tdc which is at "I" and lined the marks up on the cams with the head. Motor is getting fuel, getting spark, motor is brand new and has lots of compression, I just took everything apart. No bent valves or anything. Valves are adjusted properly. I switched cdi boxes, stators, ignition coil, batteries, the only thing left is the flywheel. Maybe the guy dropped the flywheel when he took the motor apart and the magnets inside maybe have broken and are throwing off the spark. So basically the quad is firing too soon I believe. It makes a small backfire out of the intake, so i thought the spark timing was off making it spark too early when the intake valves are open. I have tried everything but the flywheel, which i am going to try tomorrow. If anybody thought it could be something else, that would be great. Thanks.