Jump to content
Sign in to follow this  

03 450R won't start after rebuild

Recommended Posts

OK, a friend of mine has an 03 CRF450R that had a rattle in the bottom end so he decided to rebuild the whole motor. We replaced every bearing in the motor, and after re-assembly she won't fire up. After several kicks we get a single fire through the exhaust. We have been over the timing at least 4 times and it appears to be timed properly. All timing marks on both sides of the engine and the cam gear line up with their marks and the intake lobes are facing the rear of the motor. Is there something that we may be missing? Any suggestions would be welcome at this point. Thank you,

Josh

Share this post


Link to post
Share on other sites

First things first, did you test for spark. Also check you kill switch I have seen many people go thru everything and it was kill switch.

Share this post


Link to post
Share on other sites

Yes, there is spark, thus the backfire. No, it is not the kill switch. We have been over that. The fire reliable as well. Any other suggestions?

Share this post


Link to post
Share on other sites

Can you bump start it?

Did he install new valves and are the shimmed to spec?

Consider that the valve seat may be worn out and need to be recut.

Share this post


Link to post
Share on other sites

I have a 03 crf and have found that the timing marks do not line up perfectly. I had the same problem once and it ended up being a timing issue. With mine it was super hard to kick over. There are other posts on this site about the timing marks on the 03's not lining up right.

Share this post


Link to post
Share on other sites
I have a 03 crf and have found that the timing marks do not line up perfectly. I had the same problem once and it ended up being a timing issue. With mine it was super hard to kick over. There are other posts on this site about the timing marks on the 03's not lining up right.

Yep, like this one. its for an 07, but same idea

http://www.thumpertalk.com/forum/showthread.php?p=7798598#post7798598

Share this post


Link to post
Share on other sites

Sorry I haven't been maintaining this post. We have been out of town and nowhere near a computer. We did not do much with the carb other than removal and replacement. I believe that this is valve related, we have since discovered that the compression is near nothing and the intakes are pretty tight. He is looking this over now, there is a chance that we did not get all of the shims back in their original locations. I will let you all know what we find. Thanks for all of the replies.

Josh

Share this post


Link to post
Share on other sites

OK, we got it started, turned out that we had misplaced the intake shims. Swapped them back to original locations and she runs strong now. We apparently made another mistake though, she rattles pretty good in neutral now, and we can't get it to shift into fifth gear. Any thoughts? Looks like we are going to have to split the cases again,but if anyone has any ideas they are more than welcome. Thanks,

Josh

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
Sign in to follow this  

×