"Updated Parts" Update

So here's the news. I finally picked up my 450 from the dealer Thursday and had it at Dumont Dunes all weekend.

Dealer repaired as per instructions from a Yamaha representative who was there. Dealer states Yamaha feels it is being caused by jetting that is too lean, causing a backfire during e-start that shears the key. They said they rejetted the carb and installed a stronger woodruff key. The part number for the key on my receipt is 90280-03001-00. I'm curious about whether this is in fact a new part number compared to the old key. My receipt also shows they replaced the spark plug, part number CR8E, an NGK plug.

I don't know what they jetted my carb to but now it runs like crap on the low end. It ran great opened up on the dunes but it would not idle and wanted to die whenever I was coming to a stop. Furthermore, I could only start it with the cold choke even after extended periods of wide-open riding. (It was about 50-60 degrees up there, but I wouldn't think that is cold enough to require the cold choke after long riding).

On the other hand, I used the heck out of my e-start, way more than I did before the initial key break, and I've had no problems.

So, now I need to figure out my jetting to get that bad boy running like it was meant to.

Did you remove the exhaust baffle? What Pilot Jet did they install?

FYI The 90280 03001 00 PN is the woodruff key for WR 426's.

When I lapped the crankshaft I replaced my original key with a new key that was the PN shown in the manual. I will check to see if they are the same PN's.

UPDATE My dealer says the 90280 030001 00 PN is the same PN for the WR and YZ 450. So I can't understand how it would be a more robust Woodroff key unless a batch of their keys were under specification.

Dealer states Yamaha feels it is being caused by jetting that is too lean, causing a backfire during e-start that shears the key.

Hmmmm. I thought it was the e-start too, but there are at least two posts here that I've read where the key sheared while the bike was being ridden.

Maybe in those cases the key was already sheared but the rotor didn't go far enough out of time to prevent it from starting and running.


That makes a lot of sense since the damage would have already been done. I was wondering the same thing, could just riding shear the key, not likely IMO? Others have reported their bikes running but not very good with a key on the verge of shearing.

Hick thats good thinking, gives another explaination to the problem presenting it self. You a smart mofo :)

In another post from today a guy noted that the fit between crank and rotor is what really secures the thing in place. The key is just to locate the thing on the crank. I think that with all these keys getting sheared there is some kind of fitment issue with the stock rotor.

So I was puzzled to read this post where the Yamaha rep said it was a torque and jetting issue. I don't own a WR, but if I did I don't think that would do it for me...

All of this was with the exhaust baffle in. Midway through the weekend I took it out and it seemed to run a little better.

I'll be taking the carb off soon to rejet and I'll post here to let everybody know what Yamaha had them put in. It should say on the jet, right?

BTW, anybody know what the part number for the GYT-R exhaust insert is? I'll do a search of the posts...


I am also suprised they said it was a torque and jetting issue.I brought my bike in when the key sheared at 120 miles.The dealer called Yamaha and they told him to lap them together.That was a hundred and some odd miles ago.I will be checking the torque tonight when i get home.

I have been using only the e-start when i'm riding with my buddies trying to get it to break.(After its warm)I am getting more and more confident that the bike is fixed.

I wasn't real happy pushing the dang bike for a couple miles till i got towed by a zuk :).I love this bike and hope it gets worked out so this is a distant memory for everybody.

Some more info: The 450 manual suggests retorqing the rotor nut after XXX interval of riding. I bet the YZ, and Wr426 said the same. Next couldn't you shear a key if the bolt wasn't tight enough and or the rotor to shaft fit wasn't good ,if you had accellerated very quick and then locked up the brakes causing the rotor to want spin off the driving shaft.

A previous post said that Yamaha replaced the woodruff key with a stronger one, but when I looked up the key PN it was the same one in the wr450 manual and was also used on the YZ 450 and Wr426. Maybe the keys they used were a bad batch and contributed to this problem.

It should say on the jet, right?

Yep, the size (or PN in the case of the needle which I doubt they changed) is stamped on the part, small type but visible to the naked eye (with good lighting).

Well, I think I figured out why my bike ran so crappy this weekend. I took the carb out to do a few things, jetting, throttle stop, etc. and found that the dealer apparantly failed to re-install the pilot screw. I presume this is likely responsible for the bike's refusal to idle and poor running at low throttle settings. I'll post soon when I discover what jets the dealer put in.

So, the jets in my carb after dealer service are a 65 starter jet, 45 pilot jet, 70 pilot air jet, and a 150S main jet. What does the "S" mean after 150 on the main jet? I wish I knew what the jetting was stock so I could tell what they changed. Anyhow, I am going to research jets here on TT so I know what to get tomorrow. So far looks like 160 MJ, 48 PJ, and maybe try a 72 starter jet?

The dealer called today - My WR450 is ready to go. It received an updated flywheel and a carb "adjustment". I'll post part numbers and the results of a weekend of merciless flogging when they become available.

On the positive side, it took only a week at the shop including parts shipping and it was a no-questions-asked repair. If the problem is really fixed, then I'll consider this a totally acceptable solution to a minor manufacturing glitch. We'll see...

did they tell you what the diff. was in the updated flywheel ?

I knew it was more than torque!!! :D :D :)

Hey Eric,

If Yamaha has really solved the problem, one ride on the WR and you'll forget Honda ever made an XR600... :)

I can hear my dealer now.."the bike has no design flaws when rode in the designed peramiters, 30 mph on flat ground, in 70 degree weather. Since you took out the baffle re-jetted, cut the grey wire, your warranty is nul and void " :D :D :D Seriously,even though some of you might not want to hear this; even in my industry one vendor, outsourced to produce one part, can wreck the whole machine, there were 2 fatal aircraft accident due to a $5.00 cotter type pin :):D I don't know if yamaha manufactures the flywheel or if they use multiple vendors for the same part. But all it would take is one lazy,hung-over machinist to make an .001 mistake for one day and wreck alot of "our" days. Hopefully Yamaha has figured out the problem and doesn't want to come out with the fix until it is 100%. Why use some half baked fix, have it break again and have us all po'ed again? Maybe I'm drinking the blue Koolaid but I think when they have isolated the source and have a 100% fix we will all find out. Heck even my buddies that ride orange know about this now, Yamaha is not getting good press right now for their WR's. I love mine, let them ride those slow orange bikes :D :D

I agree. I bet the new flywheel has a better taper fit!

Has there been in failures in the last week?? I havn't seen any so maybe the thing is fixed. I hope so cause I'm suppose to be picking mine up in 2 weeks.

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