Has anyone shorn a second key?

7 replies to this topic
  • sabooo

Posted January 29, 2003 - 11:15 AM


I'm just curious if anyone has had a woodruff key replaced and then shorn a second one also. Shearing one may just mean that the flywheel nut was not torqued to spec, shearing another after replacing and correctly tightening the nut would indicate more of a problem.

I'm not sure the problem is even slightly related to the starter, as some are reporting the bike shuttin off while riding as well...

Watch this space.


  • WR250fla

Posted January 29, 2003 - 11:39 AM


Great question that I was wondering myself. I'm taking mine in tomorrow because the dealer called me today and said they want to check something related to this problem. I'll post what I find out.

  • sabooo

Posted January 30, 2003 - 10:24 AM


bump. :)

  • Hick

Posted January 30, 2003 - 11:26 AM


I'm not sure the problem is even slightly related to the starter, as some are reporting the bike shuttin off while riding as well...

I don't know either, but I can't understand why it would fail otherwise. All it has to support is the inertia of the mag, and it has some help (unless the theory about loose mag bolts from the factory is accurate).

I did see the post where the bike quit while running, it could be that the key was damaged during starting but the mag was only off a few degrees, then as the ride progressed it moved to the point that timing was retarded too much for it to run.

I know the YZ (almost surely) has a lighter mag, but I still think there haven't been any woodruff failures on that bike because it doesn't have the e-start. And a lot of guys have weighted their YZ flywheels.

I just don't see how a woodruff key could fail without a lot of help from a rigid opposing force like a starter gear. But I'm just speculating about a bike I've never even laid eyes on, so what do I know?? :)

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  • beezer

Posted January 30, 2003 - 12:02 PM


Speculating on a bike you have never seen is half the fun.

Seeing one never stopped me from giving out worthless advice.

  • David_Gronlund

Posted January 30, 2003 - 12:30 PM


We've already determined that the key shearing has nothing to do with a starting problem. The bike won't start after the key shears because now the flywheel is no longer connected to the crankshaft. The starter turns the flywheel that turns the crank and starts the engine. No fault of the starter.

The bike dies for the same reason. The flywheel holds important electrical components that turn with the crank to make the spark timing exact with the crank revs. If the flywheel is no longer turning with the crank (because the key holds the flywheel to the crank) then no spark can be generated.

This can be from many reasons, but my guess is that some assembly line workers mistorqued the nuts on the shaft and with the added wieght on the flywheel from being a WR model and the starter gear it would shear off easier.

Lock-tite and retorque, end of problem. I'm guessing this was an early release problem and no later release bikes will have this problem.

  • slomo138

Posted January 30, 2003 - 05:14 PM


The woodruff key is not used to hold the rotor on.It is only used to locate rotor to crank position for timing purposes.They use the torque of the nut on the rotor which has a tapperd hole in it to press it on a shaft which has a matching tapper on it for holding.
When I took my flywheel off to replace my woodruff key the fit between the flywheel and crank did not feel as tight as on other bikes I have owned.I pressed the rotor onto the crank by hand without the key in place and was able to spin the flywheel freely.All the other bikes I have worked on when doing the same thing have all had some type of friction.
To me it seems as if the taper might be off slightly.It seems a little tight on the out side or small dia. of the rotor hole.I will bring home some spotting dye friday and see how they match under different torque specs.If they are off slightly it can usually be fixed pretty easily by lapping the two surfaces together with valve grinding compound.

  • Hick

Posted January 30, 2003 - 06:45 PM


We've already determined that the key shearing has nothing to do with a starting problem.

Fill me in so I'll quit making myself look like such an idiot. Who is "we," and how did y'all arrive at this conclusion?



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