WR450 Starter Update '03 to '04 Part Numbers

Well here's my 2 cents. I've had an '04 for almost 2 months now and have put about 600 miles on it. As BajaFool said we disassembled the idler gear/torque limiters on our bikes and compared (his is an '03). I do not believe there is any difference in the crankshaft taper or diameter all though we did not measure it. IMHO the problem with the '03's is not the woodruff key. That is just the symptom. If you look at the '03 starter drive it is clear that it cannot turn backwards. If the engine kicks back there is nowhere for the force to go except into the starter drive. Actually you are lucky if the key shears because if it doesn't something else is likely to break instead (there are some other posts describing this). In the '04 you can turn the crank backwards with no issue since it has the torque limiter which slips under those conditions. The lean jetting that the '03's came with aggravated the problem. I think if they had been jetted properly from the factory the problem still would have existed but it wouldn't have been so widespread across so many bikes. Basically it's a weak design coupled with poor jetting. I believe the '04 is a much better design and will probably prove to be very reliable. Only time will tell.

I ordered the parts today for the conversion. :) I hope it works without having to modify something. Who has actually done this conversion or did Jeff pull the covers off and compare the 03 and 04 models. Thanks again for the research TT members. :D

So INDY is going to be the first guinea pig. Thanks :) I guess you must of changed your mine I thought you were not going to mess with it till it broke. I guess we will have to call this the JP_INDY mod :D

I didn't pull one apart but I compared the manuals on both and confirmed with Yamaha on which items we need. I am trying to get Yamaha to pay for mine, so I haven't ordered them yet.


Yeah I changed my mind :) because it makes technical sense that if I were ever so unfortunate to get a backfire and the woodruf key does not shear the starter gear make break into small pcs and make a mess of the engine. But I still feel I can get away without the upgrade. It may take Yamaha 6 months to get the parts to us so you are going to have to wait for the results. In the mean time I am considering just riding until I have a failure and then swap out the parts. :D Any opinions out there would be appreciated. My bike has been fantastic so I think I will press on. :D I ride so much that I keep spare body parts, bars, damper parts, pipe & header, cables, levers, busters, computer and misc items that always go and soon I will have the true TSB woodruf solution found on the 04's! :D

Must be nice to have so many parts on hand. :) I Had mine fixed with only a few miles on it and have not had a problem since. It would just give me a bit more reinsurrance if i put the new toruqe limiter in. I usually start my bike by what ever it takes wheather it's giving it a bit of gas or ect, never had a problem with it back firing but what does concern me is when your going fairly slow over somthing technical and it stalls with a bang and I always cring and cross my fingers and hope it starts I am not totally sure if this stalling can effect the woodruff key. Can it? Also let me get something straight we can save a couple hundred dollars by using our old side case by building a simple bushing? True? :D


We haven't seen the case yet so we don't know exactly the difference, besides the bushing. Yamaha may have fixed the area that has broken on some bikes. Also, the case is about $80 not a couple of hundred. :)


I am with you BigD450. I always cringe when it almost stalls during a big hill climb and it refires up could it backfire? :D I still think jetting is crucial if you dont do the upgrade. I ordered the cover as well because I thought the old cover would not allow space for the torque limiter from earlier posts. :)

hello fellas, ive been following this posting with interest as this is whats happened to my 03 model, it backfires when off the throttle. Ive now broken my case and chewed my starter gears up twice. Ive got an fmf ti 4 fitted and didnt really think it needed jetting as it pulls fine. Im assuming thats whats caused it. look forward to hearing if mod works.

does the backfire only do damage when using the button?

Bajafool and I compared the '03 and '04 cases pretty carefully although we did not remove them to look inside. They appear to be identical with the exception of the bushing in the '04. My guess is that they are the same casting. To answer your question Dossyboy anything that causes the crank to kick backwards can damage the starter drive. Kickstart or E-start it doesn't matter.

Has anyone cracked their case cover from the starter kick back??I think that mine did...i posted awhile back about my starter making a weird noise and have been tracking the noise,it sounds like the idler gears are not engaging.I decide to pull off the case cover to see if maybe the starter clutch bolts had backed out alowing too much play ...a tech at the dealership heard the noise and told me to start there first.I removed the cover to the idle gear and noticed a crack in the casecover where the idle gear shaft fits in the case cover.It allows the gear to move around too much ...so the starter won't always start it just spins.

i wonder if this is caused by starter kick back,and if it is covered by yamaha.I know that when you crack you're case from the kick starter kicking back and breaking the starter stop that they won't cover it...can't talk to anyone at yamaha till tuesday!! :)

PHATKID, your problem is exactly the result of the poor design of the starter system and idler gears. Like a lot of us, you will need to replace the parts I have listed here. That will make your '03 just like an '04. The Torque Limiter is the main change, it will absorb the energy from an electric start kick back.

Maybe we can get Yamaha to give us all a good deal on the parts, rather than the $350 retail price. I have written a letter to the V.P. of Yamaha Motor Sports and asked him to help me.


I have ordered the parts at full price. :D Please post any sucessful efforts to get help from Yamaha regarding this issue. I will let everyone know when I get the parts. :) it could be a while since they are 04 parts. I hope we do not get any more cracked engine cases. :D

Please post pics and instructions on the task when you accomplish it. I am not educated on the starting system yet.

Count me in! Here is quote from my post on "03 wr450f letter to Yamaha"

My WR is in the shop for the fifth repair. 1) Woodruff key broken. 1A) Called me to bring the bike in per the service bulletin. 2.) Woodruff key bent enough to prevent the motor from running. 3.) Shop tech must not have tightened the starter gear attached to the back of the fly wheel allowing some of the bolts to back out and chew up my coil/stator. 4.) This time I took the bike to a different dealer after it lockup and quit running. The new tech claimed that the last tech did not loctite the fly wheel resulting in a broken center case and pages of other parts. 5) While on my fourth ride since the last repair I stop the motor to rest, when I tried to E-start it would not turn over. When I tried to kick start it the starter was stuck engaged. It’s back in the shop again. Yamaha has paid for the repairs, but how many more times must I be towed out of the woods. I'll tell you now! NOT ONE MORE TIME!!! I want a reliable $7,000+ dollar motorcycle! Not the piece of s^&*&^ I'm stuck with now. It's almost a week and I still have no word form the dealer confirming what failed this time. I will push this up to the top of Yamaha USA management. My last resort will be a lawyer!

One of my riding partners has been riding a 99 WR400F and has been following this issue closely. He has been a loyal Yamaha buyer for many years and his 2 kids ride TTR's.

He was so impressed with how Yamaha is handling this issue he went to the Honda dealer last week and bought his very first HONDA. He got a CRF450F. We rode the woods together and he says it turns a whole lot easier, and he luvs the bike... :) IF YAMAHA doesn't provide a "free" upgrade to the 04 model starter system, I will become a very loyal HONDA buyer....

I wanted to bring this post up to the front again. I havn't heard anyone reporting that they got the parts to upgrade the starter system. I know some of you have ordered them so whats taking so long?

Parts will most likely not get here until the spring. My experience with new model parts is that they all go to production first and then they make some for worldwide inventory. :)

My WR went ot the shop Monday for its third key repair. This time its getting a new crank and fly wheel. They are checking on the new starter parts. BTW I got something else today to ride while my Yamaha is broke.

I gather that once you have had a key shear and damaged the flywheel to cranckshaft fit you are more susceptable to another shear failure. I wonder how many of these could have been prevented by checking the tourque on the flywheel nut before riding. Thanks to the guys here at TT I had heard about acouple of failures and one of the first things I did when I brought mine home from the shop in Feb. was check and retourque the flywheel nut. Sure enough the nut only had about 25 lbs. of torque on it. I torqued mine to 65 which is about 10 more than I think is specked. Wonder if this is why mine hasnt failed. Wish I or we or mainly YAMAHA had made more of a to do about checking the dern flywheel nuts. Tim

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