Crankshaft Bearing jammed

Hy guys,

I've been a great reader of all your posts here in the forum. I never had to post anything since now. I used to own a 2003 WRF450 that I put onto road in the summer.

A few weeks ago, me and friend went to the New Brunswick, in Canada, we are from Québec. During the journey, my bike start to do some clacking noise like when your valves need to be adjusted. The sound was going worse and it became really unpleasant. Monday morning, we decide to take my bike to the nearest dealer, in Moncton. There was 3 km left qhen the engine staled. Enough gaz, enough of all, the engine was dead.

So here we are, the dealer take a look and tell me that no wrf450,426,250 crank bearing would be enought strong to support my type of riding, street use. By the way, I had put two more teeth on the counter shaft sproket. He told me that he's rebuilding many of this wrf crankshaft & bearing because people are riding their bike at constant speed for long time, even on the long rocky montain trails. I new that this motor was not specialy designed for that type of road and that's why a was never running at constant speed, releasing the gaz and turning it often. I'm really not rough on the mecanic.

I was really surprised that nobody else on this forum as already got this problem on his bike also. Maybe I never saw the post he had writen too.

Finally, I let my bike to the dealer with its bill of about US$900 and shop for another. That's where I found my new 0KM KTM SM '02 that was much cheaper than my WRF450 with all the stuff on it, US$5000. I had look for ktm before buying my exYamaha, but it was way more expensive. I should have met this ktm dealer in Moncton before!

So this was my first story and maybe the last on this forum unfortunatly.

Thanks guys for your posts!

This is your first post? with a crank bearing gone bad and a new KTM?

What da hell is zat?

Interesting post..

I dualsported my '02 YZF 426 about 3000km ago and I haven't stopped since. I rarely hold a particular speed for long and the max I'll run the bike w/my 14/47 gearing is about 70kph.

I too have been thinking about getting a big KTM for increased engine reliability. That said, the thought of less 'flickability' doesn't intrigue me all that much. Maybe I'll test-ride a Katoom first.

Cheers, Darryl

Yes it is,

I unfortunatly had a bad experience with my wrf450 which I now know it's not build for my type of riding. What's getting me mad is that my ex dealer and other one told me I will never had problem with it even if I'm doing long ride.

The wr450f is an awsome bike and it has a lot of power. I would keep it without any doubt if I was not doing so much road.

By the way, I forget to mention that it broke at nearly 4000km, about 1200km after the last check up.

It is well known that all dirt bikes have a hard time with transmission issues from heavy street use. Dual sporting a dirt bike means occasional street use. Not sustained long high speed runs. The WR450 transmission will not like that. As far as your crank bearing it may be that the oil just got over worked since there is only 1.2 quarts of oil in it you need to change it every few hundred miles. The gear box lubrication and filter/carb system is not designed for sustained long runs without contamination or breakdown of the oil. :)

Strange story...Was a crank bearing really "jammed" or seized? Was it not your flywheel woodruff key that broke loose?? How hard did you push it? 16/50 sprockets would give you lots of speed; about 103 mph at 10500 limited rpm. I run 15/50, much like 14/47, (99mph@10500rpm) and can cruise comfortably at 50 to 70+ mph. This is not a two stroke. No need to screw around going on and off throttle...Anyhow, your dealer probably made up that story... :)


I think you hit the nail right on the head....

Bonzai :)

Street & OEM dual-sport bikes typically have rubber bushings in the rear hub to absorb the stresses transmitted to the engine. On the dirt there is a lot of slippage on accel and decel between tire and trail, therefore, they have the sprocket mated directly to the hub without the shock absorbing bushings. On the street it is an entirely different story...very hard on tranny's, chains, cranks, etc, if the hub is not rubber bushed. If I were going to do significant street miles I would definately opt for a quality bushed rear hub. It'll save wear and tear if not the entire motor itself.


I would think a "non-cushed" rear hub might be hard on the transmission, not the crank! Think about all the shock we give the motor off-road. 10k Rpm panic rev and then an immediate bog when we hit the ground short. Wild wheel spin then lock up the motor with the rear brake.

I have another theory:

1.2 qts of oil, and we know at sustained high speed (highway) riding, the WR is gonna blow tons of oil out the breather. Ergo, instant seized motor.

I never liked the idea of a 1.2 qt dirt bike that blows out the breather. All for what, to save 1lb?

Just my 2 cents

It all goes to the crank my friend...everything. Not that there aren't other posibilities here, my point was simply the fact that they aren't "cushed" and I wouldn't do significant street miles without one.


the suzuki drz s dual sport model does not have a cushed rear hub , other than ktm i know of no other mfg that offers a cushed hub as an accessory :)

cycle canada recently had an article on converting a wr450 for motard use and also noticed oil venting from the crankcase during a high speed track sesion . if wr's were designed to be ridden on the street they would come with turn signals from the factory .

Flashers from the factory thanks to the Australians:



Now how come Yamaha USA can't sell the same bike here at home??? I'd of picked it up without blinking an eye.

I remember seeing a WR250 two stroke that is also street legal down under, and I can understand that 'cause it's a 2 smoke.

Nothing against my WR's but, I'd of loved the opportunity to purchase a street legal CRE250 or a WR250.

Here is the Australian YZ250WR...Of course, if GregVince let his WR450's small oil amount run low and/or old, as the pre-seizure noise suggests, his crank bearing may have succumbed from lack of lubrication.

I was also wondering why yamaha gives an australian version of the same bike that is street legal. This is the same bike.

During my trip, I often looked at the oil level because I'm aware that there is not too much of oil for that kind of motor. I had also plane to change my oil half way just to be sure of its quality, doesn't cost so much to get my mind free...

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