I was riding my 1970 T500 and my left cylinder went dead on me, no noises or anything it just died, luckily I was close to home and managed to limp back home on one cylinder. I immediately pulled the plug and noticed the electrode had just about melted together because it had a small piece of metal stuck in between the electrodes. No hole in the piston, no scorching, burns, or other visible damage to top of piston, cylinder walls as smooth as glass, etc... But I also found a couple of tiny pieces of metal inside the exhaust port... I pulled the jug and low and behold the skirt on the piston facing the exhaust port has been completely shattered!!! The top of the piston looks fine and there is no damage to the rings, etc... Plenty of two-stroke oil seems to be getting to the cylinder, crank, etc... It seems "most" of the pieces of the shattered skirt ended up in the exhaust pipe; I found them there after I removed the pipe and baffle, then lots of tiny pieces fell out. I believe the piston is a genuine Suzuki piston; top of the piston has an "L" on it with an arrow, which is correctly facing the exhaust port. The piston is also correct for the 1970 T500 because the skirts are solid (pistons for the 1968 Cobra are different and have a hole in the skirt). I have done a little research and unfortunately it seems that shattered piston skirts like this are not all that uncommon on the T500. I am just getting the thread started here so I have some questions:
*what are some causes for this type of piston failure - too lean fuel mixture due to carb settings (jets are stock); pre-ignition due to incorrect timing; crappy piston design, etc...?
* just prior to this the plug had completely fouled on a prior ride. A week or so later I changed the plu with a new one, which was in use on this fateful excursion.
* Plugs in the bike were a B7HS, though many people use them I now realize those are not truly correct, they may be too hot, I purchased some B77HC plugs and will use those in the future on this 70 T500 and already put them in my 68 Cobra.
*with regard to fuel mixture I have a habit of putting the 91 octane lead-free gas in my bikes (no more) and in the fall I had loaded this bike's fuel up and ran it shortly with what I now think is too much stabil fuel stabilizer for fuels with ethanol, along with a strong dose of sea foam for winter storage! Even if its not the problem, I now use the lower-octane fuel AND the correct mixture of fuel stabilizer.
*it seems "most" of the piston debris ended up in my exhuast pipe; but what about potential debris i the crankcase? This is an "early" model T500 and has crankcase drain plug holes; could I pour say diesel fuel into the crankcase and attempt to wash out smaller pieces? Does the case have to be split?
*Should I replace the piston with a genuine Suzuki piston, or go with say a wiseco? If I go with something else, it's obvious I should replace BOTH pistons.
* I managed to remove the exterior piston pin "circlip" that holds the piston in place with the piston pin on the connecting rod. However, the interior circlip is very hard to get to. Is removing the other jug the only way to get more space to get to the other circlip, or does someone have any special tricks they can share?
Obviously more to follow, thanks to all in advance for reading and offering some potential advice, Eric
1968 Suzuki T500 Cobra
1970 Suzuki T500 Mark III
1970 Kawasaki 500 Mach III - H1
1970 Yamaha R5