Thread: what you guys think happen?
02-14-2011, 02:48 PM #1
what you guys think happen?
this are my 250x pistons.only modification is timming 6 degrees. i think is manufacture problem.
02-14-2011, 03:27 PM #2
i think you had too much timing not a manufacture problem. also maybe to low of octane fuel.
02-14-2011, 04:06 PM #3
Could be detontation. Dont know if Kawi has knock sensors. On a SC jet they should.
02-14-2011, 05:13 PM #4
I've had FOUR pistons do that to me in the last year, yes 4! All on separate occasions. First was w/ timing, next 3 were stock timing. This is definitely a manufacturing issue, however good luck getting it covered. Against my better judgment I ended up just buying a new boat. Sorry to see this happen to another person. I hope you have better luck than I did.
02-14-2011, 06:58 PM #5
on 07/08 pistons
09 pistons have a thicker crown to stop this prob, as well as the increased COMP ratio
Timing alone isn't the cause
I ran 10 degrees for best part of a year on 1-1 pulley on my 07 OEM pistons NO problem ( I dont recomend doing it by the way )
another person ran 1-1 only and same result
I have also seen many stock boats do the same ......
02-15-2011, 07:21 AM #6
02-15-2011, 12:16 PM #7
I have one of those pistons sitting right here on my desk that I helped a friend with last year.
The part of the piston to look at is the underside. See how it's a gold color with that nice blue/green rainbow? It's heat related for sure.
Way to much timing, continuous use of low octane fuel, high hours at elevated timing, to hot of a plug, will all cause this. Whether it's from us modding or just the nature of the motor oem, who knows.... Typically, it's not something that happens overnight, but a continuous run of being on the edge.
From what I remember being told, #1 cylinder seems to be the one to keep an eye on for heat with that motor too.
Never heard of a 260 piston cracking though so the extra thickness seems to help a lot.
Madrui, do you have pics of your spark plugs that were in the ski when the piston cracked? Can you post a few pics of the plugs so we can see a good clear pic of the entire ground electrode?
02-15-2011, 06:51 PM #8
02-15-2011, 07:18 PM #9
Either on stock or modded ( go figure....distrubition problem in Mannifold or cooling jackets I guess )
They did show similar under side , But when u look closley you might see ( well the few I have done did )
They crack from top side of pin up the side threw the ring lands over the top of the crown and down the other side inline with the gudeon pin.....as per your shots
Traditionaly a det failure will just eat away the centre/thinest part of the crown...........
i bet if you compare the underside of all 4 pistons only the broke 1 is darker colour
I see this happening as the crack happens and the crown opens up the extra compression/heat pass's threw the crown super heating all the way threw causeing some oil burning marks on the under side..
So in saying that I am 100% sure its a OEM fault considering on ski only had 45hr & was STOCK and the other was a hard life ski.... and both showed identical failure results............
I am not saying timing cant ............just 6 degree on good fuel is proven safe.
p.s 1 of the repaired skiies which got 260 pistons has run for 30 +hrs on 6 degrees & 1-1pulleies now in race application ( bit less timing for the enduros and when we pulled it down = perfect
02-15-2011, 07:33 PM #10
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