Mechanical Summary of the 98 race season

The initial tear down of the motor revealed several problems. First on the list is an oil supply problem. The cam bearing surfaces on both ends of the camshaft were destroyed by lack of oil as were the bearing surfaces of the cylinder head. The exhaust side rocker shaft and rocker show signs of severe heat and wear. The lack of oil supply was due to several problems, the oil suction strainer was clogged with debris washed out of internal oil passages, the top end oil restriction orifice is apparently too small, a small rubber sealing washer between the cylinder and head needs to be replaced with an o-ring to provide more room for oil flow to the head and the design of center crankcase gasket seems to severely limit oil return flow to the oil pump, also the oil return flow passage to the oil pump needs to be enlarged. The clogged suction strainer is due to an insufficient cleaning of the oil passages when I reassembled the motor, next time I will do a better job and also remove the clutch cover and clean the strainer after run in. I will install a Takegawa high volume oil pump for the 99 race season.

I also found sever scoring on the top side piston skirt, I'm not sure of the cause. The piston to cylinder clearance was rather loose when the motor was assembled despite the fact that I had the cylinder bored to match the piston at my local Honda dealer. The wrist pin showed signs of overheating and over spec clearance.

The gearbox seemed intact, the shifting problems appear to be caused by a combination of a worn shift plate, an old shift detent spring and an ineffective shift linkage designed by myself.

Although the motor was running a little lean it does not appear to me that it was lean enough to cause any damage. There was no blistering on the plug or damage to the piston crown. The combustion chamber and piston were clean and covered only by a thin gray coating. The exhaust valve shows a reddish color. The cylinder wall shows some scoring on the top side but not deep enough to be felt.

Valves, springs, retainers etc. seem to be in good shape. No metal particles were found in the oil or crankcase. residue of burnt oil could be seen and smelled in the cylinder head. Most parts coming in contact with the camshaft show signs of heat i.e., blue or blackened surface and burnt oil residue.

Destroyed Parts
Cylinder head
Piston  and wrist pin         
exhaust rocker
exhaust rocker shaft

Parts now suitable only for low performance applications
Camshaft  (maybe a total loss)
Crankshaft and rod
Cam chain

In the next week I will post pictures of the damaged parts along with other photos of important pieces, I welcome your input as to the condition of these parts and the cause of the damage. The piston damage is a mystery to me, after I post the pictures I would welcome any information of what the nature of the problem may be.