Broken case at timing chain guide

9 replies to this topic
  • rezman

Posted January 09, 2015 - 03:48 PM


Hi all.. enjoyed reading the old threads on the YZ's.
So I bought a winter project... a non running 2005 YZ450F.
I know, I know I should have waited until I found a running machine.
Went into this expecting to rebuild it but I keep getting deeper.
So the latest issue is the left case has a small ear broken off. At first thought no problem but now I figured out the front timing chain guide bottoms out against this.
So the question is has anyone run with this issue? Wondering how badly the guide will wear. Could I epoxy the piece back in? THANKS for taking the time to read this....

  • grayracer513

Posted January 09, 2015 - 04:42 PM


If the break is above the arrows in the picture here, and the area outlined in red is intact, you should be able to run it.  The front guide is also anchored by the head, so it can't get up and out of the pocket without being forced. 

Attached Thumbnails

  • Untitled.png

  • rezman

Posted January 09, 2015 - 07:11 PM


Its exactly the lower part you highlighted in red.
Thanks Grayrider... I know you try to help here often.

  • racer8

Posted January 09, 2015 - 08:10 PM


Is it something that could Possibly be welded?

  • grayracer513

Posted January 09, 2015 - 11:29 PM


If you have the piece that broke off, it could be "fairly" easy to weld it.  Depends.  Should be reinforced, though.  If it's missing, you'll either have to have something fabbed and fit, or replace the cases.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • rezman

Posted January 10, 2015 - 03:01 AM


I found the piece so will look into welding.
This bike will teach me a lot... should have bought a runner.

Cylinder head intake cam journal scored.
Piston scored
Cylinder damaged
Wheel bearings shot

So have a crank kit coming, new std cylinder, and once the gaskets arrive will send the head out with the valve seals.

I got my wish oh what a project.

Thanks again Grayracer and others for your time.

  • rezman

Posted January 16, 2015 - 09:03 PM


Picked up the case today... They were able to build up the area and machine the pocket back into it. TIG welding for $70.00 not to bad. It's only money.

So now trying to figure out what broke the ear off to begin with. The timing chain guide does have a mark like it got smacked by the balance shaft counter weight.

Don't think a kinked timing chain could force the guide towards the crank.... any ideas?

  • racer8

Posted January 16, 2015 - 09:35 PM


During Maintenance sometime in the bikes life, Someone may have tried turning the engine over while the timing chain was bunched up down on the crank sprocket.

  • grayracer513

Posted January 17, 2015 - 09:55 AM


That's possible.  Probably more likely than a broken timing chain, too, but it could also have been just about any kind of loose piece of metal that tried to get between the two parts. 

  • rezman

Posted January 17, 2015 - 08:48 PM


Thanks for the replies...

Had a good day, got the engine cases back together, wheel bearings changed out.
Was a good day to use the oven and heat up the cases for bearing install.
The "wife" is not home this weekend so there was no b**ching about the smell.

Related Content


Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.