Preliminary data on woodruff key failures

Yamaha won't have to do anything about the design, the key is suppose to shear, it is there for alignment only. The tapers hold the rotational torque that is applied to the flywheel. If your bike hasn't sheared a woodruff key and you have retorqued, chill.

You seem to want to get others worked up. There is no need to blow this into a bigger deal than it already isn't. Again I ask "Do you have a custom pot stirring stick?"

gsxrguy, I think the updated update for torque is 47 lbs.

The manual started out at 50 lbs. Someone at the factory thought 61 lbs would solve the problem. So all manuals were updated with the paste-overs. Then between Japan and the USA someone else decided 47 lbs was the correct setting??? :)

I was finally able to get my WR450F to the dealer for service yesterday (damn snow). They told me today that the woodruff key was sheared (duh) and the parts are on order.

I've talked to the dealer service manager and someone at Yamaha, both assured me not to worry about it. I've only been worried about this because this is my first new bike and I read all the stories about the valves on CRF450's last year. I know how Honda has always been absolutely loyal to their customers on new models, often after warranties expire, but they dropped the ball on the CRF. I've been afraid that Yamaha could do the same about our flywheel keys.

But - they haven't before, and it's not expected that they will this time. I predict that my WR will be fixed permanently when I pick it up. If it's not, I'll give them time to work it out.

Besides, there's still three feet of ice and snow on the trails. Not like I can ride anything right now anyways.

Bean 329, adamwager, thanks! I'll go to my dealer tomorrow and see whats up? they usualy don't know much. also I was told the was no warranty.

gsxrguy, 3 things, 1- I have not had a yamaha in a while but i do believe that yamaha will warranty manufactures defects for 30 days. 2-If you broke a flywheel key you will need to remove the mag cover to replace. 3-If you cannot do this repair then make sure you have a competent mechanic do it right.

Ice "the key is suppose to shear", you must be kidding.

My Goodness, do you think that tiny key is suppose to hold anything, it is there for alignment. Taper, Taper Taper.

Thankyou Icebox I agree completely.Alignment and timing mark.

Please don't make excusses for Yamaha's key problems! Honda's XRL's and new 03, CRF230 start forever without a problem (no key failures on the Honda site). Suzuki's DRZ's, KTM's and Kawasaki's all do not have this key problem, and have electric starters. Yamaha choose to reduce weight at every opportunity, and this is the risk they took! Stay on em and they will have to solve the problem. Accept it as ok, and it will be our problem at our cost. $$$$ :) I guarantee you people will have keys break after the 30-day warrantee. WHO will PAY for that? It is a great bike and I luv to ride it, and have 120+ miles in 3 weeks, and will do Enduros with it. Don't misunderstand my desire to keep Yamaha responsible for key failures. It is almost a perfect designed ride! I bet the 04's will have different KEY design, thus Yamaha admittance of a problem. What I want is Yamaha to accept responsibility for the failures, and pay for the fix, after the 30 day warrantee, which is when most will fail.

I hate to agree with you Alabama because of your tainted history on ThumperTalk. Your a rabble-rouser. But this time your right. :)

I still think when you shell out over 6 grand for a dirt bike..... it better be right . i'm going to wait for the word from yamaha before i touch it.

Woodruff key commonly called a sheer key. Do you know what they are there for? If for some reason the engine is stopped or something goes wrong, they ARE designed to sheer. If you have the starter engaged AND the enging backfires do to jetting that is not right where does the force go? The key sheers or you suffer crank damage. Now do not think I am jumping in for Yamaha, but I do not buy into the mis-matched taper. They have made millions of fly wheel/crank tapers. Now there is a problem? I doubt it, but it could be. It is tied to the e-start and the gear/flywheel arangement more than likely. I may not be 100% correct on this but it is the most logical deduction from an engineering stand point. Was that taper and key designed to start a bike with? Probably not. They probably just figured it would work and it does. The woodruff key is the desingned week link. Flame on-----Mike

No flames here I mentioned before!!!! Why some folks interpret this as "sticking up for Yamaha" one can only imagine. :)

Since I went through a key shear incident I think have some interest in seeing a solution by Yamaha.

Mike...just remember all that when your 20 miles from the truck......WITH A SHEERED KEY. :)

thank you Adam, "this time your right"....

Alabama_Rider, I will not even comment on how silly your “you guarantee” statement was, opps already did. Secondly, we are not talking about other bikes, we are talking about a Yamaha WR450F, kin to the YZ450F. Comparing to other bikes is ridiculous; they don’t share any parts in common, they are different in every way except for the 2 wheels thing.

Do you realize that the woodruff key is there for only alignment so the timing is correct? If you do not see that, the discussion cannot go any further on that issue. The key holds no forces.

A shearing woodruff key is a by-product of the taper between the flywheel and crankshaft not holding the rotational forces at work.

What could cause that?

1. The torque on the nut is not enough to force the tapers to a respective position on each other such that the frictional forces between the tapers are enough to withstand the other forces at work.

2. Too much torque, to the extend that the tapers are being distorted. (not likely with the rumors of an air line being pinched)

3. The tapers are not fitting properly (angles are off). This could be as minor as tooling gone bad or as major as the taper angle not being adequate.

What are the remedies for incorrect taper fit?

A. Lapping the 2 tapers together with lapping compound.

B. Replacing parts; ie flywheel or crankshaft.

Another question must be asked, what is creating forces so great as to break the holding force of the tapers?

Possibilities: (running low on this one, anyone?)

1. Backfiring

2. Too strong of a starter

3. Flywheel too heavy

4. Backfiring and the starter only turning one way


A. Change the jetting, the Canadian model does run stock jetting that is richer, that might be a start.

a. Seems there has been some problems with twisting the throttle just a little to get it to start with the e-button. Some have backfired after this, Yamaha says this is a no no. Starter jet might be something to look at like utvols had suggested. 72 seems to be what he had used, again weather would play a big role in how all bike start around the country this time of year.

B. Don’t use starter, not likely, most of us bought the bike for that convenience however there could be something to the idea that someone mentioned that KTM recommend only using the starter when the bike has warmed up. The starter is small (weight reduction, agreed) and therefore can’t turn the bike over like a swift kick can especially when it is cold. (KTM claim is just a thought, not substantiated at all.)

C. The flywheel is different from the YZ450 but I have heard 2 different stories, does anybody know the scoup on this? I have read the flywheel is heavier another article says its just larger in diameter.

D. This is a new and interesting observation, Wrench let us know what you find out with this.

Since I am tired of speculation in the wildest sense, here is what I see as a logical way to approach the issue.

I am wondering what kind of stats we would find from the persons that have richer jetting, lapped their flywheel, torqued the nut, loosened and retorqued to 47 ft-lbs. (assuming 47 ft lbs is correct) Can anyone comment on this?

how do you know what the production # is ?

what part of the VIN# ?

Just in news flash, cutting gray wire sheers woodruff key, are maybe not.

Just picked up my 2003 WR450F. I live in So Cal and had to wait a day because Yamaha put a hold on the bike until they sent out technicians to evaluate all the WR450F's and show the staff a "fix". Apparently Yamaha has realized there is a problem. My bike was given the green light and allowed to be delivered. Don't have the id #'s in front of me but will get them if anyone is interested. Have 2 miles on the bike only but should be wringing it out shortly. I need to get all the info on the throtle stop, airbox and exhaust tricks. Thanks for great info.

Yah, wouldn't that be just great, all the free mods coming back to bite us. I say us in the proverbal sense, still don't have my WR.

Good one :)

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