I've had the 450 for 6 weeks now but haven't riden it much as too much rain in Houston area and I knew that the key issue wasn't sorted plus a bunch of MX by my son - so only 31 miles. Pushing 5 miles with my leg isn't an option... Been starting it with the kick - but yeaterday hit the button and it started and then backfired/died. Hit the button again and just spinning at the starter - but not turning over the engine. After 31 years on Yamaha I might be sorry that I didn't just keep the 426 or go to KTM on this one! Is this the way yours was or sounds like the starter isn't engaging. I really like my dealer - Texas Yamaha - and it kept me from going the Orange - but when I tool it in they didn't want to work on lapping the crank/key as no gaskets. etc were available - and probably still aren't. My frame is 00755. Will be at Yamaha tomorrow.