Can you spot the oil leak?

[thatkid]

I'd guess the bolt was to blame (faulty) then snapping, causing the rod to bend then snap, the piston could fall below BDC then the rod would come up and smack it causing the damage to the piston & liner, then the snapped rod has smacked through the crankcase?

I've saw this on seized engines, conrod/s and shells partially welded to the big end journal = snapped rod and big hole in the case.

[ragedigital]

now what to do with these cool smashed to shit piston and parts. makes for a good coversation piece on the garage shelf I guess ha ha

I'm sure there's a coffee table in there that is just waiting to be built...

[yamaha_george]

While I originally agreed with the "cir clips" theory, I think it may have to do with the bolts, but we'll know more when Steve tells us what the inside of the cylinder looks like. It would have to be pretty torn up.

My bet is with a con rod bolt... either wasn't installed using Threadlock, it stripped or it was a not tightened properly. Once the bolt fell out, the con rod was pulled down below the crankshaft and the piston was allowed to travel below the cylinder base and there by creating the perfect scenario to snap the con rod in half.

RD,
If that was the case I would see the bottom clamp of the conrod beaten by the crank it does not seem to be damaged.you may well be right that when the rod broke it got hit OR fell into a position where it was hit after all the conrod is severely bent by the break point.

Looking again at the pictures those two retaining clips are wire type I just hope that when Steve changed the pistons over he did not use the original wire clips but used new ones (and i am a little suprised that they were suppled on a racing engine) as we always used proper "Jesus" ** clips which you fit with proper pin nosed plier type tool.



**
For the Christians in the group they are called Jesus clips because many a Tech has said his prayers when installing them and see them slip off the tool into the engine internals or into some spider infested black hole that defies physics as being too small to receive the clip.

[reelrazor]

Steve,

Is the small end still free on the wrist pin?? Any scoring there-wrist pin or small end bearing?

How is the crank pin and big end babbit?

And, ANY damage to the cylinder head/valves in that hole?

It is my humble opinion that the rod was stretched to failure (tension failure).

This is quite often a result of the small end of the rod being restrained while inertia,the other cylinders, and drivetrain continue to drive the crank. Caused by..a) small end bearing seizure...b) piston skirt/ring land failure...c)or jammed circlips as has been suggested.

The cylinder wall being 'clean' points me at skirt/ring land failure.

I would bet the 'worse' side of the piston lower is the front side(and there is corresponding damage at rear/top of piston-and the crack in the cyl. liner is at front of cyl. block).

Just my $.02 without being able to hold and look at and smell teh parts involved...

[thatkid]

Something else should be considered, the lightened balanced crank, that took forever to be completed. I remember you had a crankshaft oil seal leak (stator cover full of oil) Have you checked all bearings/shells for wear (main & big end)

If they screwed up on the lightning/balancing well...... Kablamm!