Jetting and Timing problem solved

Well after deciding that my CDI was bad I went to the yamaha shop this morning and yamaha swore up and down that they are not having any problems with the CDI but to check the woodruff key. Since the bike ran fine with the TPS unplugged we decided it had to be the CDI but decided to check the woodruff key anyway.

Miricles never cease to happen. The woodruff key had sheared and the flywheel had rotated enough to throw the timing off but the bike would start with e-start and run. After replacing the key we settled on the following jetting:

#160 main

stock DUT needle in stock #4 clip pos.

#48 pilot

#72 starter jet(this could probally be smaller but it was all I had)

fuel screw 1 & 3/4 turns out

The blue beast is finally rocking. I will still play around with the YZF needle but will wait until after this weekends race to see how she performs.

I can not believe I have been chasing my tail for a week now but I am very happy to have resolved this issue.

How tight was the nut? With the cam change and easy starting what could cause the key to shear? My bike is not in yet, but a quick re-torque on the flywheel nut might not hurt.

Theres not any real way to tell. I used an impact to take it off so it was tighter than finger tight.

I'm assuming you used a flywheel puller to remove the flywheel and get at the woodruff key. What puller did you use?

I used the yamaha puller from the shop I bought the bike from.

I had the dealer re-torque the fly wheel before I took it home to 61 ftlbs. I hope that the problem with the woodruff keys is the incorrect torque and not an engineering problem ( I have the stickers in my manual so they must have known about the incorrect torque/shearing ). Is the replacement woodruff key a yahama stock item, or just any keyway ? Btw vols are you running stock airfilter ? Has anyone run Race fuel through yet ???

Hey it's me again. I checked torque on mine and it was good, I guess (47). After jetting similar to you it is running good as far as I can tell. My question is Could I unscrew the inspection plug, remove the nut, and with a light be able to tell if the woodruff and keyway are lined up properly. Or, would I have to remove the cover, pull the flywheel in order to see if I had a undamaged woodruff key. I have the spare key already, and it certainly is a very SMALL key. I realize that nearly all of the holding power comes from contact of the tapered surfaces. But if a very small amount of rotational pressure were to occur (ie first gear stall, etc) it would seem a larger key and keyway would overcome such forces. This isn't a show stopper problem, but I'll be happy when all early production bikes are clear of this problem or a reliable fix has been determined. BTW my bike is # 892, could you post your build number? Thanks Jim

My bike is serial #1321 and you have to take off cover and pull flywheel to see or get to the key. Also I recieved my twin air filters this week and I am running these exclusively in all my dirt bikes. As with other new models owned I always find them to be on back order until you call twin air(boysen) direct. You pay a little more but they always seem to have what I need in stock.

VIN # 0641.

I checked the torque on the rotor when my bike came in last Friday. It came loose at around 35lbs which usually means the torque was lower to begin with. (i.e. it takes a bit more to break the nut loose initially.) I think the WR's have been missed torqued at the factory.

My bikes s/n is 680ish (can't remember exactly). It's a Canadian bike.

Studded up the 450 and went woods riding. This bike is fantastic. It feels as light as a 250 in the tight stuff. Power is super smooth, no big hit like the 426.

Using my incredably accurate bathroom scale I weighed my old bikes.

97 XR600 full of gas - 303lbs

01 WR426 full of gas - 288lbs

03 WR450 full of gas - 275lbs empty 261lbs


what were your symptoms from the sheared key problem. i have jetted my bike to your specs and it accelerates like a champ. my problems are trying to hold a steady 5th gear speed, it wants to miss every few seconds. also, i have to pump the throttle one time before i hit the button to start the bike and it pops(i wouldn't call it a backfire, but almost as loud)when it starts everytime.



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