'03 WR450F Woodruff Key Blues


I was runnig stock jetting at the time of the backfire and 2nd woodruff key failure.

The local Yamaha shop saw some damage to the flywheel due to slipping and key breakage. Yamaha sent a new flywheel with instructions to lap it onto the crankshaft, apply loctite to nut and torque to 47 ft/lb. Got the bike just in time for the San Angelo, Texsas hare scramble. I changed main jet to 155, pilot to 48, air screw out 2 1/2 turns. Had no problems with the flywheel for 3 practice laps Saturday and 3 race laps Sunday. Jetting still seems lean. Good mid-range, but need more pull on top; and difficult to e-start unless the engine was very warm. Oh, my bike serial number is 1357; right in the middle of the bad batch!

im in copper canyon mexico and I think my woodruff key just bit the bullet ... is there anyway to start/run the bike once this has happened? im in a tight spot....thanks.

If the woodruff key has sheared, the bike is dead in the water, because the fly wheel is loose on the crank shaft and is no longer in time with the valves and piston. The only fix is to replace the woodruff key. Don't just limit yourself to motorcycle shops, hardware stores sometimes have woodruff keys for other pieces of equipment. Also try auto parts stores. Last resort, make a woodruff key out of steel flat stock--- check out a welding shop they are into fabricating metal parts.

My 2003 failed after I brought it home from the dealer and started it in the garage--- zero miles on new bike. No one knew about the "backfiring causes the woodruff key to shear" issue or how to cure it in January 2003. I eventually incorporated the complete idler gear mod using the 2004 WR starter idler gear and new gear cover. This is the only way to eliminate the sheared woodruff key problem permanently. I never had a problem after the update. I ride in Northern Baja California often--- sorry to hear about your problem.

If you're trying to fix it in the field your biggest problem is going to be pulling off the flywheel. Unless you have the correct puller you will probably damage the crank-end, flywheel or both.

I'm affraid you are out of luck.

thanks for the replies...got trucked out of Urique (copper canyon) to the trailer we had in Creel...Im taking it in to the shop as soon as I order the parts from the 04 models....what should I tell the dealer to look for as far as broken parts to retrieve from inside the case? i dont want anything floating around in there.


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