2006-03-13 Yamaha makes one helluva motor

Split the cases on my 2000 yz426 today. This bike is ridden every week, moto'd beyond belief. I run this bike hard. Uhh, ok, I abuse the heck out of this bike.



Recently I heard a slight low end knock. Other folks I asked to listen could not hear it but I did. Took it to my local dealer, Powerhouse, and Ivan (5-star mechanic) found a loose nut on the crankshaft and what he thought might be a failing crankshaft countershaft balancer bearing. It was this bearing that required the cases be split.



Long story short, the piston had zero, nada, zippo carbon build up on it. No blow by on the slipper piston either. Cylinder still has original cross-hatch patter on it. No lip at the top of stroke. The gearbox looks NEW. The dogs are straight, the gear interface area is not worn. Cam chain and guides are not worn. Cams look perfect.



In short, the internals look sooo good. The balancer bearing is marginal, but still servicable. The inner race has just a bit too much play.. so, just to be safe, replacement was chosen over a hospital stay. BTW, only one valve has required lash adjumstment over these 6 years.



I just hope the FJR is is built equally as well. I have never seen such a high hour engine come apart with so little wear. I mean, I have seriously hammered/abused this bike. 6 years of racing and practicing. I ride this bike every week!



For the record, I've used Champion syn oil since broken in and have changed it religously.



WOW.