Watta Ya Reckon Lozza

[Turtle.Inc]

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

nice job anyway

Always nice to kow your work is always appreciated

No reeds

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.  

Ring and rotation pin still there still there complete, stuck but complete, decompressor etc all good, retain plates centre popped and loctited,

[smed]

Run a magnet over the slug & the head,that may tell you if its bits of steel or alloy imbedded in there.

[matcho mick]

Tertell,bottom picture of piston,that bit of foreign looking material embedded above the ring dead  centre looks sus,if it;s not metalic,it's track,your;e aircleaners failed  ,

[Hoony]

no matter what has done it, you need to pull it down to the bottom end at MINIMUM to assess it.

[Canam370]

my votes on a crook bottom-end.

[Nathan S]

Part of the cage from the big end or little end bearing?

The 175 top end I had on my DT125 swallowed a rock at Canberra - I discovered it as a tiny, rectanular block lodged in the spark plug. New plug and it did three more race meets.
Eventually I convnced myself that it was down on power, so I ripped the top end off - it looked a lot like that, except the entire top ring land and top ring had disappeared.

[Snowy 76]

I Reckon your  Engine problems will help you forget your Clutch issues 

[VMX247]

17yr old boy child suggests- its detenation running too lean....cheers A
perhaps ask Lozza 

[monaro308]

Thats what my piston looked like after it dropped the little reed cage screw.

[Lozza]

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

I reckon it's gonna be expensive and you need a decent camera I doubt you have a jetting or timing issue. There looks to be no sign of detonation on the head or crown, and that thick black layer on the head tells me(amongst other things) that your still on the safe side of a seizure. I would run with the general theme of metalic objects and looking at the size of the marks I woul have said a ring expander, but they don't run them so I would agree with Hoony and say a cage disintergration with the rollers still in situ(making the big end 'feel' OK). Rollers make a big mess , but have had a KX 60 big end bearing completely vanish.
If the big end cage/thrust washers are in tact the only other possiblity is maybe something from inside the carby.

[montynut]

Turtle stop bitting your finger nails 

Have to agree with Snowy 76 this makes the clutch problems seem minor

Piston looks exactly like mine did after the little end cage failed last year on my 250. Everything bearings wise looked and felt fine until I tried to remove the wrist pin  . definitely a foreign object of some type.

[DR]

I kind of side with Alison's 17 y/o. Looks like pre ignition/detonation to me also.

[Viper666]

"I kind of side with Alison's 17 y/o. Looks like pre ignition/detonation to me also."

Me too. Had a IT175 running 125 electrics & did exact same thing.

I know there are signs of metal floating around;

Question: Is there a small fragment of spark plug missing?

Maybe a combination of both.

Had a 125 let go a bit of big end cage and looked like the piston side shot but no where near the damage on top.

Detonation are explosions of the bad type and the head & top of piston look exactly like that. You mention you changed ignition/timing?



Viper666

[LWC82PE]

What oil ratio was being used?

[Captain Bilko]

Looks like a bit like detonation but somethings deffinatly been banging around inside there. Looks like a small roller about a mill and half wide. Put us out of our misery and split the thing....