What is the purpose of the starter upgrade? ('03)

Is there catistropic failure involved without doing it, or can I wait?

As long as your bike never backfires you may be OK. An aquaintance has an '03 and has never done the upgrade and it still runs fine, but as far as I know it has never had a backfire. If you do have a problem you will be pushing or towing the bike back to the truck due to a sheared key on the crank. If it happens there is a possibility of valve to piston contact. $$$$ I personally wouldn't risk it, but that's just me. WR Dave

So what happens; does the starter clutch not disengage properly?

If I understand correctly the upgrade gives the starter gear an overrunning type clutch effect. The starter gear never disengages on these things. WR Dave

I don't remember the details, but one of two things were reported to happen when the motor backfired:

1. The Woodruff key would shear, the flywheel rotates out of position and the bike loses proper timing and stops without any expensive damage. The cost of replacing the key is only ~$2 in parts. However, if this happens on the trail you have a dead bike on your hands.

2. If the Woodruff key doesn't shear, then a part of the left case around the torque limiter/starter idler gear was known to break or crack. You then lose your e-start capability. The bike will still run (and you can still kick-start it) and get you home.

But, you really need to address number 2 above to prevent number 1 from happening. The original torque limiter was redesigned to address this problem.

Another potentially aggravating issue with this bike is the decomp lever plug (piece of pressed in rubber) on the right side of the head is known to blow out causing an oily mess (and potential engine damage if enough oil blows out). This can be fixed with the use of the TT decom plug, or by fabricating a small L shaped bracket to hold the plug is place.

Great info, thanks.


I owned one of the first 2003 WR450F's sold. I was in on the ground floor of the Starter problem. The link that follows will tell you everything you want to know about the Starter and Sheared Woodruff Key problem on the 2003 WR450F. Read the entire thread for the full story and what is involved to fix the problem. http://www.thumpertalk.com/forum/showthread.php?t=303319

I would go ahead and do the mod, it was easy, and it did not cost that much. I have a 2003 wr450, 5 years no problems.

Boy do I feel like I came to this discussion too late, but... the starter problem is covered by Yamaha and you can take your bike into any authorized repair facility to get it done for free.

The problem affects serial number range 0014-2694; (last

four digits.)

The problem is the generator rotor may not be mated perfectly to the

crankshaft. You can take it to the dealer and let them know about the

service bulletin for "'03 WR450F DAMAGED GENERATOR ROTOR WOODRUFF KEY",

bulletin #M2003-007A.

If it happens there is a possibility of valve to piston contact. $$$$ I personally wouldn't risk it, but that's just me. WR Dave

Not true... 99.9% of the cases with the 2003 WR450 it just shears the key

and then won't run because the flywheel has spun on the crankshaft and the

ignition timing is too wrong for it to run. New key, flywheel reinstalled and

retorqued, and you are back where you were before the incident. To cause

valve interference it would need to take the timing chain with it or cause it to

skip a few teeth. Not impossible, but not very likely either.

That said, my 2003 has almost 10,000 miles on it now and no issues (knocking

wood, crossing fingers, sacrficing virgins, etc). I'd say that six years on if

it was going to happen it would have by now. But if it does, the '04 parts

upgrade will ensure it never happens again.

I stand corrected, I was thinking that the sheared key also released the crank gear, my bad :worthy: -- WR Dave

well my i have have a 2003 wr 450 with the mod and yet it still sheared the woodruff key and six bolts that hold the flyweel on. so whats up with that??


You have several extra words in your comment, so I'm not sure what you are saying. However, if you are saying that you have the "Starter mod" installed in your 2003 and you sheared the Woodruff Key, please describe the mod you think you have installed.

Also, there are not 6 bolts that hold the flywheel on. There is only one large nut with a left-hand thread that holds the flywheel on a tapered shaft.

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