Anyone know how they're fixing woodruff keys?

How is Yamaha correcting this? I don't want a key like the original. It seems to me that they would be offering a harder key or something of this nature. Does anyone know if yamaha has come up with an absolute cure???????? :)

The key is not the problem. The key only locates the flywheels orientation on the shaft. The problem is the interferance fit between the wheel and the crankshaft. If it is not correct, the wheel will spin, shearing the key. If the key were harder, or bigger, a failure of the flywheel may cause catastophic damage to the engine. It is sometimes called a "shear key". I don't know why Yamaha calls this "woodruff key failures", it is not the key that is failing. The only cure Yamaha has come up with so far is to lap the flywheel/crank (use an abrasive compound to match the surfaces), and loctite the pieces together. The loctite tells me that Yamaha is not too sure that lapping alone will cure the problem. You normally don't have to locktite the flywheel to the crank. I've heard that alot of people have had no failures after the procedure, but, I've heard about a few failures post fix. :)

I understand what your saying but the only way to correct the problem without removing the crank and enlarging the keyway or something of this sort, is to change the key with a harder one or something along those lines. That is why they are calling it a "key" problem. The dealer done the lapping/locktite work on mine before I bought mine and it sheared before I could get it loaded up to bring home. What it amounts to is Yamaha should have used a larger keyway and hence a larger key.

Sorry but Lon13 is right, the key is only for alignment. It should bear no stress what so ever. The tapers are what hold the rotational forces.

Keep in mind that you are NOT assured that the TSB was performed correctly unless you are there watching and that is going on the assumption that you know what is suppose to go on anyway. How clean were the tapers, did they use the right grit lapping compound and did they let the Loctite cure for 24 hours as per Loctites recommendation.

We are also not talking about your typical Loctite from the hardware store, it specifically for taper fittings.

I wouldn't take your dealers word for anything unless you have a long-standing relationship with specific people. Call me skeptical but I was reassured that my bike was all ready to go (before the TSB came out) but upon first warm up it turns out I barely had 2 mm of oil on the dipstick. Now wouldn't you think checking the oil would have been done by the service department?

I feel that unless you use machinist dye to check the fit of the tapers before you do the TSB and then again after, that is the only way to compare what affect the lapping has done. What happens when the 2 rounds of lapping did not get a proper fit? I would suggest that some are having reoccurring failures because of just that. Better be safe than sorry... :)


Thank's for the input. It looks like I learned something today. What your saying is the nut and bearing surface of the rotor are what holds the thing together, the key is just for alignment. I get it now. In other words the lapping job is the most important aspect of the whole process???? Have I got it now????? :)

You got it Brother. If you have a bigger or harder key, you run the risk of tilting the key in its keyway. Then your REALLY screwed. Long ago, when bikes of questional build quality poured out of europe, this kind of failure wasn't too uncommon (one of the reasons for the Japenese takeover). Usually you just lapped the crank/flywheel torqued the nut and you were good to go. I've heard that this failure is popping up among the four wheeler crowd also. Probably from engines designed for bikes getting E-starters for the quad. :)

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