Finished tearing down my top end...

6 replies to this topic
  • dldavis_66

Posted January 27, 2008 - 11:27 AM


That was fun :applause:

First time doing surgery on a motorcycle. Took me about 12 hours.

As I was pulling off the head I noticed a little pile of loose deposits sitting on the piston. Almost looked like sand :busted: . On top of the piston, there had to have been at least a 1/32 inch thick(even at least 1/16 of an inch) in some places) of baked on deposits, covering well over 90% of the piston.:cool:

Oddly enough, when I finally got the cylinder off I inspected it and it didn't look in too bad of shape. The rings were shot. The cylinder came off the piston way too easy. I'm suprised the bike even ran as good as it did.

I pretty much know why there was so much baked carbon on the piston and valves. I let my best friend ride it around a lot. He says that he was not sure where the choke lever was supposed to be and it turns out he was riding it around on FULL choke:bonk: !!!! That explains the black carbon build up but I haven't figured out why there was some sandy, almost DG(decomposed granite) looking stuff mixed in with it, especially that loose pile of junk I saw laying on top of the piston.

I've rebuilt quite a few auto motors and have never seen anything like what I saw on my piggy. Really weird stuff. BAD gas maybe....kinda baffled about it.

Anybody got any ideas????

  • InTheDirt

Posted January 27, 2008 - 03:40 PM


Although riding with the choke on doesn't help. Most of your black deposit is from oil leaking around your rings. Don't know about the "sand".

  • dldavis_66

Posted January 27, 2008 - 03:50 PM


Although riding with the choke on doesn't help. Most of your black deposit is from oil leaking around your rings.

Oooooh....forgot about that,'d think I would see some grey-blue smoke coming out of the tailpipe...unless the the leak was so small it oxidized everything during the combustion....hmmm.

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  • tgstoken

Posted January 27, 2008 - 04:19 PM


Your sand deposit was probably from when you removed the spark plug. If the area around the plug isnt spotless, junk falls into the cylinder.

  • cleonard

Posted January 27, 2008 - 04:39 PM


On mine the oil mostly went in the other direction. I started getting a lot of oil out the breather. It finally got so bad that oil would drip out every time I came to a stop. I only got a tiny amount of blue smoke.

When I tore it down the piston and the bore were well within tolerances. The rings were beyond toast. I didn't even try to measure the ring end gap. It must have been at least .125 if not .200. New rings and a quick hone and all was good again.

  • Denn10

Posted January 28, 2008 - 01:13 PM


prolly build up from a light oil burning on your piston. Deposits from the oil look like that and like said prolly just a light oil burning and that will do it. With the heat these run they will have what looks like excessive buildup if you have problems ie running with choke or oil burning. GL have fun with the rebuild

  • Krannie McKranface

Posted January 28, 2008 - 04:25 PM


If the rings were shot, you were sucking oil up into the combustion chamber. The deposits you see are from that: sulphur, carbon, oil additives, etc all being burned .

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