Major Engine Work

After a long week end ride in the Mountains, I washed my 2000 WR400, Started it up to dry off, it sounded fine. I took the air filter out, cleaned it and re oiled it. I then packed it on the truck and went back to the mointains for another week end of riding. When we got to the camp site, I went to fire up the bike and it started making this terrable knoking sound. I shut it down and loaded the bike back up and spent the rest of the weekend riding other bikes. My mechanic pulled the engine apart and belives that the piston rod bearings had worn enough to cause the piston to hit the valves. I need a new rod, bearings, timing chain, ect. Does this sound right? He said if the Bike was an XR, I would still be riding it. The clearances in the WR are much tighter. If the bike was not YZ timed, would the valves clearances be so tight. This bike has alot of miles on it, but it ran great the previous week end. How could it get so bad so fast?

The same thing happened to my xr650

The culprit was a timing chain that was too loose and jumped a link.

You mech. didn't tell my xr, it was trashed :)

Sorry about your bad luck

Same thing happened to my 2000 WR400 or thats all they can think anyhow. Chain skipped causing MAJOR DAMAGE. Everything was replaced with the exception of the tranny. Crank, cylinder, piston, head etc... Original repair estimate was almost $5000 CDN! Yammy paid for part but it still cost almost 2 grand to fix!


Unless the crank or rod end bearing self destructed I can't believe a piston floating would hit the valves. I am going to go with the chain jump theory. Tell us all what your oil type and change interval were so we try not to make that mistake. (Just Kidding) Sometimes it happens, the downside of a four stroke I suppose. As far as still being able to ride the XR I think your mechanic may be a bit too opinionated and maybe even more ignorant. I don't see too many Honda mechanics in the unemployement line! This Yamy engine is a state of the art mill and needs a little TLC. Think of it like an Indy car engine, you wouldn't be too successfull beating back and forth to work everyday without causing you some trouble now and then. Performance comes with a price. Not that I generally subscribe to the maintainance schedule in the owners manual (I believe they are designed to sell parts) but I am curious How many hours/miles the motor had on it before it grenaded. Good luck getting your scoot back in the dirt!



'00 WR 400

Western Fab Insert, YZ timed, airbox lid removed, YZ throttle stop, Michelin S12's, UFO YZ plastic,Mobile 1.


I got the bike in the spring of 2000. I have had three major incedencted which may have affected the engine. 2 major water flooding incidents, the second time I had the bike out I thought I would drive along the side of a pond to clean it off, fell into a hole and almost lost the bike in quick sand, Then while wheeling across a stream the back tire spun out and I set it right down under the water. Both times I got the bike running within 12 hours, changed the oil untill it started coming out clean. In the fall of 2000 I switched to mobil 1 15W50. The thrid significant event was during a 24 hour ice race, the oil breather vent froze and the valve cover plug blew out. The bike was out on the track for over an hour untill I pitted for gas and noticed the there was oil all over the side. It reqired over a liter to fill it back up.

This bike has been ridden hard and often. I change the oil twice a month and replace the filter, every month.

Odlly engough, just befor the engine calfed I had just changed back to regular 10W40 motorcycle oil after reading about problems with using Mobil 1 in the recent Dirt Bike magazine.

It looks like the repair is going to cost between $800 and $1000 CDN so I will just call it an operating expense.

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