Watta Ya Reckon Lozza

[Turtle.Inc]

  :'(
The 490 had a little nip up on the weekend, whats your view

[Mick D]

Was that the first time out on that piston/bore Ross?

[Turtle.Inc]

Was that the first time out on that piston/bore Ross?

Five /six meetings on bore, has not been apart, went from Bing to Mikuni and reset the timing on the PVL to 2.2 BTDC, dont know wether its Timing or Carb related or both

[mx250]

That's physical damage; something metal has been bouncing around in there 

IMHO

[JohnnyO]

Looks like it's munched up bits of metal from somewhere? Somethings been hammered around on the top of the piston and head. Doesn't appear to have siezed from the pics.
Are they big end needle bearings embedded in the piston?

[Turtle.Inc]

Looks like it's munched up bits of metal from somewhere? Somethings been hammered around on the top of the piston and head. Doesn't appear to have siezed from the pics.
Are they big end needle bearings embedded in the piston?

Wouldnt think needle bearing would get up past ring, its been cooking from the top of the piston down at a guess, bigend feels good, no little end damage, air filter neat seal, no leaks around manifolds

[Turtle.Inc]

That's physical damage; something metal has been bouncing around in there 

IMHO

Bore not bad either considering, would think anything in topend would blow out pretty quick anyway

[JohnnyO]

I think i can see indentations from something steel in the alloy piston and cylinder head. Circlip?

[head]

Needle bearings dont go past rings, they come through the transfers. That is definately metal damage, some thing has been floating around in there. Really check out the big end or little end.

[Davey Crocket]

If all you have changed is the carb and timing I would say they definately play a part in it.....maybe lean then starts pinging and excessive heat so the piston starts disintigrating and thats the bits of metal jammed in the head....

[Hoony]

its DEFINITELY done the big end or a main bearing

[Turtle.Inc]

I think i can see indentations from something steel in the alloy piston and cylinder head. Circlip?

Both were intact, I'll have to get some good light down bottom end but initially feels good, will have to have a closer inspection in better light

[holeshot buddy]

most of the above
check big end or main bearing cage
it doesnt have steel reeds does it

nice job anyway

[Mick D]

I am leaning toward some sort of foreign body to Ross, but how and from where is the $64,000 question.

Is all the piston ring still there? including the anti rotation pin? What about the head of the decompression valve? still there? When the new mains went in, did the retain plate screws get thread-locker and center popped?

Lets hope its not a end cage or main. Good luck.  

[VMX247]

That's physical damage; something metal has been bouncing around in there 
IMHO

+1 + bigger than circlip !
cheers a