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B86_Racer

Possibly a broken ring?

12 posts in this topic

My brother rides an '01 YZ426 and was racing a hare scramble today and said that his bike popped and then the rear wheel locked up and it died. The motor will still turn over but I do not want to attempt to start it. When I do turn it over with the kickstarter, I can kind of hear a metal-to-metal noise so I'm thinking that a ring broke?? Any other thoughts? :thumbsup:

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Pull the head off and look for a broken piston skirt, dropped valve or broken rod (pop! sound..)sorry for your loss.........

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Take a good look at the lower rod bearing. I had one go out on the same year bike, but mine just locked up solid. :thumbsup: Let us know what you find.

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We're probably going to be taking everything apart this afternoon (at least the top end). Either myself or my brother will be sure to take pictures and post back. I really think it's a broken ring though...just a hunch. :thumbsup:

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lower connecting rod bearing siezed... :thumbsup:

looks like time for a new crank and a new top end while were in there.

also, can you lap the valves on these heads? figured I might as well while it's apart

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No, you cannot lap titanium valves, it will ruin them. You can cut the ti valves and there seats but it requires specialized equipment and from what I hear not many shops will do it.

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Thanks for the information. :devil:

I priced parts tonight and I think it's going to be about ~$500 for a new crank, top end (including timing chain, piston, rings, gaskets, wrist pin, etc.) and a few other odds and ends that he needed. Not bad..coulda been worse, for sure! :thumbsup:

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That's about what I spent in parts to do mine last spring. You might as well change out the Crank end bearings while your in there.

Bonzai :thumbsup:

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Well, it looks as though the crank end bearings (#7 on the "Camshaft Piston" fiche ) are on backorder. Do you think it would be just as good to go to a bearing shop and get a couple of them made?

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So if no one says any different, I guess we are going to take the old crank end bearings out and get some new ones made at the local bearing shop... :thumbsup:

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