what could cause this???

[t3rmin]

Regular should be fine unless it pings. For whatever reason my 750 pings on regular in weather above 70 deg F, so I put plus in it and no more pingey. Probably carbon buildup or something. Ultimate ping test is going up a hill in a fairly high gear at low RPM. Peg the throttle and listen.

[Calvin Blackmore]

http://perso.orange.fr/laverdamania/pistongb.htm

nice page with root cause analysis stuff

[NATEO]

http://perso.orange.fr/laverdamania/pistongb.htm

nice page with root cause analysis stuff

Dang, my work web protection blocks that site... I will check it out when I get home...

[chef1366]

I still stand by the molten lava. (Not too close though) :-D

[49er]

I still stand by the molten lava. (Not too close though) :-D

Aren't you confusing it with the effects of one of your hot Indian curries?\\/

[Jethro]

what is the recommended grad of gas for these bikes? last summer I was using premium, but I read over the winter that I dont need to, that regular is fine for the older engines...

My 06 FZ1 runs better on regular than anything else. You should never need anything more than regular on a GS or just about any other bike IMHO.

[Dave8338]

How long did you run the bike before you started having problems? That sure looks like an oil issue to me. I'd suggest pulling the rod on that hole and have a look. Can you get a picture of the cylinder that the piston came from? As it is the exhaust side (most heat), check out the valve(s) as well. Quick and easy is nice, but with that much debris I wouldn't be able to put that thing back together without a complete teardown and sleep at night. Hey....02 cents.

[Dave8338]

It is hard to tell, however, it looks as if the rings were all put on with the ends lined up...this could also cause a melt down. Just can't quit looking at those pictures and trying to figure out why! Broken ring starting a chain reaction?

[49er]

the remaining piston crown is black, a lean condition would lieve the crown a light grey to white, also lean conditions will normaly melt a hole in the thinest point in a piston and with GS's that is dead center.

detonation is the spontanious uncontroled ignition of the AF mixture and is commonly caused by several factors, wrong grade of gas, excessive combustion chamber temperature, carbon build up, fault or defect in piston allowing a hot spot to form, incorrect timing advance.

if you gouged the piston while scraping it with a screw driver (bad idea) that could have givin it a place to form a hot spot, combine that with running hard and poof toasted piston.

a coworker of mine has a PWC and melted a piston in a similar but not nearly as severe fashion and his crown was a very light grey pointing to a existing lean condition I had warned him about (he had been complaining about stumbling and a surge) your piston crown looks black from that picture.

It is true that a severe lean condition leaves the crown area a light greyish colour during "melt down". The owner has said that he ran the engine after the piston failed and that there was losts of smoke coming from the engine. This is why the crown isn't coloured gey. If it had been shut down immediately after failure, it would have looked light grey! Obviously, the spark plug was still operating on that pot after the melt down. The fact that the engine smoked a lot after the piston failed indicates that the oil feed on that cylinder was adequate.
Check out the posted link by Calvin Blackmore for confimation of the cause of this piston failure. It also has some good info on piston suitability for vaious states of engine tune.

[NATEO]

It is hard to tell, however, it looks as if the rings were all put on with the ends lined up...this could also cause a melt down. Just can't quit looking at those pictures and trying to figure out why! Broken ring starting a chain reaction?

the rings were staggered. the top ring was placed where the meltdown occured, the middle ring melted away, and the bottom ring is broken.


right now I have the causes being a combination of slightly lean condition, hot spot from screwdriver (preignition), lack of oil (the bike was leaking pretty good. I thought I had enough oil in it, but I could have been wrong.)and whatever the hell could have gone wrong going wrong at the same time... I blew a fuse, too, but I doubt that would have anything to do with it... and my headlight.

[U.P.dragracer]

better check the intake boots for air leaks cracks etc. I bet you had a bad seal at carb #4 and it burned up that piston . I have seen this numerous times on older bikes and snowmobiles :shock:

[catfishk]

i once ran WAY too much boost and a turbo car and it had pistons like that when i tore it open. i think you need to check your turbo pressure! haha

[SPARKSS]

If the other 3 are normal, then it's a one-of-4 problem (obvious eh) and was most likely caused by excessive lean condition in that one cylinder. That took a lot of heat to melt that badly. You'll be into more than a light hone on that one cylinder (besides the obvious). Had you synched the carbs recently.....did this one take a considerable adjustment (may indicate carb problem or intake leak between the carb and head)......a leaking intake or exhaust valve will compound the problem as well. If the companion cylinder seems to have aluminum deposits on it's plug, indicating that it also is experiencing heating, you might also check the ignition timing for that pair.

[tkent02]

Just curious, is this engine original from Suzuki, or has some boneheaded P.O. ever "rebuilt" it?
Could have had some problem like improper cylinder clearance, rings too tight, or some other issue.
But most likely I would go with the way too lean concept.