03 YZ450 _ New Top End - Can't Start

I'm glad I could help...although I can't take full credit. I discovered this problem in another post on TT from 2002! After my bike gave me fits for an entire afternoon and evening, I spent less than an hour researching on TT...problem solved! I've actually been using the resources on TT for a long time...I'm glad I finally joined the fray.

On a side note, there's an article in the March '05 issue of DirtBike (106) that shows a great photo of what this problem looks like. Even though the bike in question is a CRF450, the article still shows a very clear picture of a shim sliding to rest against the side of the bucket.

Hey, I'm thrilled my first post on TT was a good one...guess I better get back to work now.

Mint! :):):p But....you didn't mention lack of compression in your post. Was there a noticeable loss or could you not really tell from kicking? Maybe with the auto decomp it's hard to tell.

I really didn't notice the loss of compression and I thought it was because of the auto decomp. Even after reading the posts, I went to the bike to check to see how the compression and thought it was ok. I was wrong.

After the problem was solved, I immediately noticed a substantial increase in the compression even with the auto decomp.

Now keep in mind that this substantial increase was not just an increase during the "no start" time after the rebuild. It was also a substantial increase over the compression that it had prior to the rebuild. The motor had alot of hard hours on it and it was tired and due for a rebuild.

So, for me it was hard to tell.

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