never seen this one before so I thought I would tell all. My stock all original 2003 WR450 is street leagle so it has many many miles of road and trail ridding. I would guess at 25,000 miles on it. I did good maintance on it allway. It had a tune up this early this summer and the valves were checked but needed no adjustment as almost allways it does not need any adjustment. Lately it is hard to start, but runs great. Then I noticed it started useing oil and had never use any oil before. They the last two days it would not fire up so I tore it all the way down today and this is what i found. Before the motor was out I removed the water pump
cover to remove the two coolant hoses and I alway try to turn the impeller of any motor I rebuild just to check to see if the impeller will spin, and it did. I have had banshee's before were the impeller would spin because they were made of plastic and got loose. After I got the motor tore down I removed the water pump shaft and slid into the counter balancer shaft were it would go and it just spun in the shaft. looking into the balancer shaft I could see it was all wore out and the flats were gone were it would drive the pump shaft. I have been ridding all over with it like this and did not even know it. Now I need to add the counter balancer to my list. I even have a digital coolant gauge on it and I thought the gauge was crapping out because I seen it doing weird stuff you normally would not see. The temp would go from 150 degrees to 210 in 7 or 8 degree increments all with in 10 second and do the same thing in reverse order. It was doing this all the time the last 4 or 5 time I went ridding. I thought the cylinder and piston would be junk, but all looks brand new with the crosshatch on the cylinder. The ring end gap is still in spec. The main bearing have to much slop and I could move the crank up and down a very small amount when the crank was still in the bike. I could hear a noise when ridding at a slow steady pace. I had guessed that was what it was, and I was right. The reason it would not start was all three intake valves were so tight the valves were not closed tight. I will be replacing everything on this rebuild so I can beat it for another 6 years. I am very impressed with how durable the WR 450 motor is.
I got lucky finding this problem and it could have tuned out to be alot of extra work and costs to have of just put it back together and ruined it agin.
Something to think about