The dealer said this forum overexagerates

I'll probably get crap for even suggesting this but replace the idler gear too, with the new unit at 36.00 bucks I'm sure anyone would have paid that not to have to push out a bike. We race, my rider is most comfortable on the WR, that's reason enough to make the bike as reliable as possible, remember no DNF's. Yamaha started testing and in some cases replacing them in some units, when I first heard (months ago) some dude in New Zealand or Austrailia had a number I got my dealer to order one it was installed approx. 2 months ago and when I put it in I marked the position and checked it yesterday the marks are 180 degrees apart so there are some kick backs. Ours failed in the driveway (Feb.)the crank and rotor were replace (no loctite) and no problems since (10 GNCC Nationals and countless Harescrambles) A 2004 WR has been purchased for next year and the 2003 will serve as a practice bike. We pay cost for the bike and a discount on parts (same deal I could get anywhere) the money I get from the dealer is just about enough to cover putting his name on the bikes.

What is the deal with the idler gears? Are they working? Is there part numbers and diagrams? Or are we all waiting on the 04 to see what the fix is?

part # 5TJ-15512-01 the deal is that they should absorb the kick back by slipping instead of shearing the key. In my experience they work see post above yours.

I agree that Yamaha is at fault. But, some Yamaha mechanics are just dont know a wrench from a ratchet. The dealer I bought my bike from has not had a returned wr due to the woodruff key. Why? Because there is only one mechanic and he wants every bike to run great out the door. Out of the crate he resolves the issue before selling the bike. I have almost 2000 miles on my bike and havent had problems. I know between the 2 shops they own at least 30 WR's were sold and 0 have come back for the said issue.

How hard is the idler gear to install? Do I need special tools, or is it a 5min. job in the driveway? Any quick instructions?

Just trying to work out exactly what cause the problem.And is there a preventative measure that is easy to do.I have been having problem starting my bike.It used to backfire when releasing the throttle so i turned my pilot get out to 1 & 1/2 turns , this stopped the backfire but made it a pig to start.I have since turned it in to 3/4 out , it starts easy but i worry about the backfire causing damage.

It's not the minor backfires you hear on's the huge backfire/KICK-BACK that occurs during starting because the throttle got opened slightly, but enough to lean the mixture and cause the dreaded kick-back that breaks the key.....

The minor backfires/popping you hear on decel are normal for a properly jetted 4-stroke and are due to the over-rich mixture which is caused by the high vacuum created when the throttle is closed at high rpms. Don't worry about them....

There is a dealer recall.

You can download & print it from's Project WR450F.

Who's you're dealer ?


Thats the lapping and glueing mod.

Sounds like a porno movie.

Wrench- thanks for the heads up on the idler gear, ordered one today. :)

I think the dealers and the magazines get very intimidated from the internet. I dont care how sharp a magazine group is, they are never going to have as much information as a group of 100 or so owners in real life.

I think sometimes they feel they must do anything they can to make the forums look bad.

wrench, whats different about the idler gear you're talking about, my motor is torn down right now and I want to get one put in if it helps.. We replaced the large gear the first time we replaced the starter clutch because it had some wear from the clutch, is that what you're talking about??


The idler gear 1 is under the the 2 bolt round side cover look at page 4-81 of your manual bottom 3 pictures. The idler will slip at a lower torque than the previous one. The gear tested by people on this forum claim that the original idler set slipped at a much higher torque than the new one. Something like 87 ft lbs vs 24 ft lbs I think. All I know is that Yamaha isn't saying anything but my original didn't slip (I marked them) and the new one does. I think it costs about 56 or 58 bucks list, I think I paid about 36 for it. We have enough crap that we can't control to worry about so it was a no brainer for us.

By looking at the part number it looks like a genuine yamaha part. But how is this idler gear diffrent from the one that is in the bike, is it a diffrent part number or did yamaha just fix the idler gear so that it will slip with less force. Also is it only the idler gear 1 that you want or need to fix this. :)

the current number is 5tj-15512-01. the old number is no longer available. it is the idler gear that looks like a double gear on your parts blow up. it is made up of two pieces pressed together. yamaha must have changed a tolerance on the mating surfaces of the two gears to allow some movement. for them to have given it a new part number and raised the price $20.00, they must have changed something in the manufacturing process. the new price is $58.00.

It is the gear # 1 in this picture, they changed the part#

the new # they added the -01-00 on the end! original was

-00-00 & is discontinued. :)

Here is the link to the parts catalog picture, you may have to move your mouse over the actual picture (gear parts) & wait a little while for the arrow to pop up to maximize the picture, then just click on it - then see gear #1!

How's that? am I good or what! :Dbeer.gif

Are there any other parts needed when this gear is swapped with an updated one?


Ride fast - take chances



Mine tried the same thing. I went straight into the GM's office and introduced myself. I explained my concerns and told him how many bikes I have bought for good measure, and he took care of me. The Service manager still does not like me but he didn't buy the bike. The coolest part is when I do go in the GM always says hi and makes sure all is well. Might not hurt to go around the service tech. Most of these guys don't give a s**t about us. Try it, it worked for me.


Sounds alot like NC Yamaha! Had the exact same experience. I won't get my bike serviced there.

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