Broken part in motor, please help!

I went riding today, and after a landing my bike started making a clicking noise. I thought it was a valve issue, so I took the valve cover off and found everything intact. So then I took the leftside crankcase cover off, and found chunks of aluminum in it. When I got I drained the oil and looked around for what part was chipped off. It turned out that the aluminum tab that holds the white timing chain guide in place was hit by the counterbalancer and broke off. In the pics you can see the damage:

Then the tab:

I am asking opinions if I can run the bike the way it is with that tab broken off, because there is still some of it left that holds the guide in place, or if I need to get someone to weld a piece on the case to help hold the guide in place better, or.....if I need to replace the case entirely. Thank you in advance!

My only concern with running it as is, would be, why it broke in the first place. I mean, there is obviously something loose or out of kilter, if the counter balancer struck it and broke it off. I think I would be pulling it apart and finding the root of the problem, then decide what is needed to repair that tab. Good luck, and let us know what you do or find out. :thumbsup:

Well I believe the root of the problem was a faulty timing chain that came from the factory. Two of the links had wedged themselves together making the chain stick out in that area, which I believe knocked the tab out enough for the counterbalancer to hit and break the tab off. I have replaced the timing chain, but ran into this problem today.


Check your valve timing! Check your valve timing! Then check your cam chain tensioner. What has happed is the cam chain has become or became loose enough to skip a tooth. During that process, the chain bunched up down at the crank, pushing that aluminum casting off. Please see:

Same thing happend to my '02. The good news (if you didn't bend your valves!!!) is that YES, you can run it that way with no problems. My '02 went over 200 hrs that way and is still running fine (although the guy I sold it to hardly rides it;different story). I would not be surprised to find your valves are ever-so-slightly bent ( the source of the ticking sound) I hope not for your sake. After you check and possibly return your cam timing to stock, if it starts right up, you should head to Vegas!!! Because you're a lucky SOB. Hope this helps...... :thumbsup:

Well I just made sure there weren't any more fragments in the motor, put it back together and checked the timing, and it runs fine now! Thanks a lot guy's!

You should also replace your timing chain tensioner with a new '04-up version or replace it with a manual one!

I should have clarified that this is 2006 CRF 450. I don't know why it happened, but I have less then 6 hours on the bike.

I should have clarified that this is 2006 CRF 450. I don't know why it happened, but I have less then 6 hours on the bike.

this is why i just hate the auto tensioner,

i have seen lots of problems like this with all the bikes all throughout the years :thumbsup:

you really should jam your tensioner so it wont do this again,

actually we all should be running a manuel unit in all reality :thumbsup:

you should see the problems these auto tensioners are causing the 06 yamaha 250f bike :confused:

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