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Missing cylinder dowel pin


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I'm in the process of rebuilding the top end/valve job on my '07 525. Just as I was about to drop the new cylinder/piston in place I realized that I was missing one of the 4mm cylinder locating dowel pins. I have no idea where it might have gone. It might have dropped into the crankcase as I was removing the cylinder, it could have fallen out somewhere between the bike and the bench, dropped out as I was packing it up to send it off to Dave Hopkins for his advice on whether or not it was still useable or it could have stayed stuck in the bottom of the cylinder. Dave wasn't able to find my old cylinder to check out whether or not it was still in it as I bought a 540 kit to replace my old cylinder and was sold a replacement part. No blame on Dave as he wasn't expecting me to quiz him on this. He likely has dozens of old cylinders setting around so finding my old one would be a guess.

Dave offered advice on how best to flush the pin out if it was still in the cases — Dilute any remaining oil in the bottom of the crankcase, lift the back of the bike rotating it forward until it is upside down and blast away with brake cleaner/compressed air, etc. After trying everything he advised and anything else I could think of the dowel is still a no show. I rotated the crank to make sure that it wasn't setting in the teeth of the counterbalance gears.

I don't have a flywheel puller but after as careful of a search as possible without pulling it I can't see it in there.

Any other ideas on where it might have gone inside the motor or how to find it?

I strongly believe that it either is stuck on the base of my old cylinder or it fell out somewhere other than inside the engine. I think I would have heard it fall if it went inside the motor.

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I would pull the engine, pour some kerosene or diesel into the crankcase and wash it out. Turn it upside down and use your air blower to dislodge the dowel if it happens to be in there.

Turn the engine back over and pour a quart of oil in the crankcase and spin it over by removing the stator cover. Pour the oil out and assemble your engine.

Your only other choice is to split the cases. Tough call.

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Man I feel for you also. It makes my stomach turn just thinking about it. The aforementioned ideas sound good and I dont have any better of an idea. Its some what time consuming pulling the motor and everything when you are ready for the rebuild, but you got to be sure.

These motors have secret ninja hiding spots. We still can't figure where all the oil goes that disappears from the sight glass and later reappears.

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