How does the cylinder get oiled? (03 yz 450)

I just siezed a brand new top-end with a cp 13:1 piston. the piston started to gall up and smeere aluminum all over the inside of the cylinder. rear wheel just locked up out of nowhere while cruising down a trail at ocotillo. bike has less than 1 hour ride time after fresh top-end

I took it to CP to ask them why they thought that would happen on a fresh engine and they insisted that there was not sufficient oil to the cylinder.

So the big question is.. How do the cylinders get their oiling?

is it just oil splash from the crank? or is there like and orfice that squirts it up there for wrist pin lubrication etc? I know there is a mod on the 450 quads to drill into the oil galley and effectively oil the top end better but not sure if it applies to the dirtbikes.

Maybe one of you experts can shed some light on my problem.


Its not the splash method, I am pretty sure of that, The oil comes up the connecting rod.

Just as a suggestion I always replace the oil pump when doing any major engine work, not very expensive part to make sure the lifeblood is still pumping, part no. 5TA-13320-00-00.

There still could be a blockage somewhere else in the oiling system, check the frame filter and all other oil passages. Pics would help.

The YZ450 pressure feeds the connecting rod by passing oil from the right crankcase cover to the end of the crank. There is a seal at this point that could be damaged. Oil then flows to the rod via drilled passages in the crank, and oil is thrown off the crank pin to lube the cylinder. The quad engine had a problem with cylinder oiling, but the bike engine did not.

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