First indication of that something was wrong i got at the end of last year. The engine didn't rew as easily as it should and it seemed a lot weaker at the top. Didn't have the time then for a inspection. First inspection this year showed that the RC-valve cables to the top cylinder were loose and that two screws to the RC-valve thingy on the cylinder was gone (later found on the engine covered in tar). Perhaps the vibrations made them unscrew themselves. Now, thinking I'd found the solution to the problem I continued with disassembling the bike and cleaning it.
Problem 1
Later, after removing the reed valves i could spot some little shiny metal objects at the bottom of the crank case housing. Intake to top cyl.. I picked up the objects with a magnet (so they are not from any aluminium part, but a bearing perhaps?). Metal objects What do you guys think the metal pieces come from? I am going to disassemble the engine later so we will know for sure later (if not the pieces came from outside the engine...)
Problem 2
Next step was to remove the cylinders, and what I saw then was not so nice. Top piston (without the piston ring on top). Obviously the piston have been exposed to extensive heat near the cylinder wall causing detonations. But why? Perhaps to little oil mixed with the gas? Bad jetting?
This is the bike set up:
Oil pump set to max.
165 main
Type B needle with the clip in the middle (i think)
42 slow jet
Two oval high flow air filters
HRC pipes
Parts from HRC wiring harness modified to stock harness, only changing ignition
Running on 98 octane unleaded gas
Running on Castrol TTS fully synthetic two stroke oil
Problem 3
There is also wear on both pistons at the exhaust side. Lower Piston & Upper Piston. The guy I bought this bike from was smart enough to fit the pistons with the piston ring opening towards the exhaust port, making the rings bend slightly in to the ports and making massive wear at the nicasil. The guy i later payed to replate the cylinders sent them to a company in England, which I think was Langcourt. Do they have a good reputation? I wounder since I think the replating of the nicasil was badly done Top Cylinder & Lower Cylinder
I have ridden the bike approx 4000 km since the replating, when I also installed new pistons with rings. And it was perhaps 1500-2000 km since I changed the setup of the bike with new pipes, air filter and jetting.
_________________
MC21, GP-Replica (Daijiro Kato, Telefonica Movistar Team 2001)
Last edited by Bodoe on Sun Jun 10, 2007 9:47 am; edited 1 time in total