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what could cause this???

  • Thread starter Thread starter NATEO
  • Start date Start date
Doesn't look like it could be anything but heat from friction, which would equal an oiling problem, as already said.
 
#4 piston. I doubt it would be an exhaust leak. the pipe for that cylinder sealed well. the #2 and 3 pipes didnt very well, so I would have expected issues from those, not #4.

what makes the most sense in my mind (I know, I know... stop thinking lol) is that when I had the head off this spring, I was cleaining the top of the pistons with a screwdriver:oops::oops: and I probably knicked it, creating a hot spot... the rest of the cylinders are perfectly fine... oh well... Im gonna check out the oil pan, screen and stuff, then slap the new block and pistons in...

thanks for your help, everyone... and that piston will definitely be a paperweight!
 
The NOS needs to go to all the cylinders, with a boost in fuel supply for cooling and lube.:twisted: But seriously that picture is exactly what I visualize when I read one of Kevin Cameron's articles on detonation a while back. Hot spot-preignition-detonation-top ring failure-flame front travels down side of piston-melted mess.
 
slugsride said:
The NOS needs to go to all the cylinders, with a boost in fuel supply for cooling and lube.:twisted: But seriously that picture is exactly what I visualize when I read one of Kevin Cameron's articles on detonation a while back. Hot spot-preignition-detonation-top ring failure-flame front travels down side of piston-melted mess.
Click to expand...

so basically, me and my damn screwdriver... I would rather that than plugged oil line or something... I can learn to not do stuff like that. plugged oil lines are different
 
NATEO said:
so basically, me and my damn screwdriver... I would rather that than plugged oil line or something... I can learn to not do stuff like that. plugged oil lines are different
Click to expand...


Hmmmm. At very high RPM that by itself might do it, but for most of us something else would have to start it down that path like lean mixture or oil problem. The nick may have moved the focus of the detonation away from the piston crown where you normally see it (as earlfor said earlier). Since it's just one cylinder check the under piston oil sprayer on that one, but I think something went very wrong with the #4 carb or intake boots.
 
slugsride said:
Hmmmm. At very high RPM that by itself might do it, but for most of us something else would have to start it down that path like lean mixture or oil problem. The nick may have moved the focus of the detonation away from the piston crown where you normally see it (as earlfor said earlier). Since it's just one cylinder check the under piston oil sprayer on that one, but I think something went very wrong with the #4 carb or intake boots.
Click to expand...

I was running it at a very high RPM when I think it died. (I stopped and then I had trouble. it ran, but not strong, and it was burning oil- the rest of the engine was pulling it along, I guess) the bike was running lean last summer, and while I adjusted floats, it could have very well been a lean condition combined with a hot spot, and very high RPM (I dont have a tach, and I may have run it too high.)
 
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.
 
focus frenzy said:
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.
Click to expand...


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...
 
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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.
 
NATEO said:
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...
Click to expand...

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.
 
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.
 
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?
 
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focus frenzy said:
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.
Click to expand...

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.
 
Dave8338 said:
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?
Click to expand...

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.
 
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