What are your thoughts on this?

scooble · Post by **scooble** » Fri Aug 31, 2012 11:00 am

looks like debris to me as detonation normally occurs at the front of the piston, or could it be that the piston is hitting the head?

Luders · Post by **Luders** » Fri Aug 31, 2012 11:09 am

I was wondering if something had been sucked in through the carbs to have caused this, as there is no airbox on this bike.

maccas · Post by **maccas** » Fri Aug 31, 2012 11:11 am

What does the head look like? The same I presume

Dan

Luders · Post by **Luders** » Fri Aug 31, 2012 11:14 am

That's what I wanted to know, it's not one of mine you see.

I imagine there's a distinct finish around the squish band to match.

dave32 · Post by **dave32** » Fri Aug 31, 2012 12:21 pm

If it was dirt/debris from the intake then the skirt will be scored up.
It looks like the exhaust side of the crown has started to melt?
You need to put a pic up of the ring lands,its pretty hard to tell from that 1 photo and of the head if you have it.
Detonation from too advanced ingnition normally shows up as the crown melting and the ring land melting on the exhaust side,a lean mixture can show up differently.

Luders · Post by **Luders** » Fri Aug 31, 2012 12:56 pm

he said the skirt was scored up, but no barrel damage fortuntely.

Luders · Post by **Luders** » Fri Aug 31, 2012 2:19 pm

Turned out to be the little end bearing had collapsed

KFOR · Post by **KFOR** » Fri Aug 31, 2012 10:20 pm

Infact both bearings at the same time but no damage on the other head.
We live and learn

dave32 · Post by **dave32** » Fri Aug 31, 2012 10:53 pm

Really,both small end bearings collapsed at the same time?
Looking at the piston again it still looks like det,if you look closer the piston crown has deformed at the exhaust side then worked its way round the edge,the next stage would be either the ring land collapses or the centre of the crown has a hole punched through it.
if thats just damage from a bearing letting go i cant see how the damage would be so uniform,there would be damage all over the crown.
Little ends dont usually let go,even after high mileage,they let go when there overheated.
so maybe the bearing collapse is a result of a problem not the reason for it.