01 WR426 Broken TIming Chain Q's

2001 WR426F. Stock exhaust and intake. Bought it from original owner 6 months ago. I have about 10 hours on it. Had to clean the carb but otherwise, started 1st-2nd kick religiously, and idled/ran absolutely fine. I was SO happy with this bike.

Yesterday my kid and I went to our local mx track. He just sold his lil CRF150 and hasn't found it's replacement. I took three "grandpa" laps on my WR and came back to the pit. (I'm an old dez rider, so jumping ain't really my thing). Jr had a long look on his face cuz watching pops ride ain't fun, so I handed my WR over to him. He made four laps, barely clearing the jumps and just putting along. Next thing you know, bike stalls. I thought maybe getting low on fuel, put on reserve and set kicker at TDC. Pulled decomp and kicker stopped again. Hmmmm. Something ain't right! Tried a few more times and no fire. No crunchy sounds from downstairs but kicker stops unless decomp lever is in.

Rolled it into the pits, loaded up, brought her home.

Tonight: Pulled off cam cover and spark plug. Timing chain is broken. Gently cycled kicker and piston sounds intact. Flywheel rolling right along. No crunchy noises.

What next? I've rebuilt a buddies old KLX300 (PITA POS!) so I have a general idea about putting on a new chain, but my big concerns are deeper than that.

Ideas? Thoughts? What to look for? I had already purchased a full gasket kit as one of the lower gaskets was weeping, but was gonna wait for winter project. Should I just pull the head and get it over with?


Jim in AK

Edited by marbee40

May have found the problem! Pulled the flywheel/stator. Down in the galley below was what appeared to be a 1/4 of a piston ring....say WHAT? Where the hell did that come from? I hadn't pulled the cams yet, so got pulling them. Betwixt the cam cover and cam is a small guide which is a half-moon shape and thickness of a ring. Kinda keeps the cam from wobbling, I suppose. Well, there is one half-moon above each cam. Both were there. Held one of them up to the broken 1/4 ring that was in the bottom galley. What the hell? Looks suspiciously just like it! Grrrr. I'm thinking a lazy friggin mech misplaced one many moons ago and thought "Oh well...job security!" DAMMIT!

The good news is the piston and valves look amazingly beautiful! Rings are fine, too. Utterly friggin amazing. Kinda pisses me off but I'll throw a new chain and a fresh set of gaskets on tomorrow and see what the hell happens.


Jim, WOW! Lets hope you found the problem, and without doing major engine damage too! :)


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