Hi after a request for more info in the wanted section.... see below
Was on a trackday on Monday when after only 12 laps my st150 (running 220bhp) decided to go pop. No warning with good oil pressure and good temperatures with rev limit set to 7000rpm.


And another

Ouch.

U have no idea about that but i would guess it to be mechanical seizure.

Can you get the piston out?
What is on the other side of the piston?

Pre det is terrible for rods, timing and CR all srnsible?

Are they standard rods and pistons because they are only good for 200 hp?

Time for forged rods i think

quote:

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Originally posted by big-vee-twin
Are they standard rods and pistons because they are only good for 200 hp?

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I thought standard internals were OK up to around 200bhp. At least that's what I recall the Burton tuning guide suggests.

Hope you can recover it!

Can't see on the pic, was the big end bearing OK?

Have you got the head off, any damage up there?

Bad luck mate.

We tell you more if you post a picture of the bearing and the fracture surfaces.
But as there is no bluing around the crankshaft end visiable in the picture I would first be checking the facture surfaces for evidence of a fatigue failre.

SBD recon 210 IIRC is the giddy limit on stock internals. However, I'm really gutted for you. You have my sympathy - it's a rotten thing to happen.

Looks to me like the broken rod may just be collateral damage, the piston must have failed first or the little end of the rod would still be hanging from the piston. Either piston seized and gudgeon pin was ripped out the piston or over revved and piston kept going at the top of the stroke.

Checking for damage on the big end bearing may give you a clue as to cause of failure depending on which side the damage is.

Is it possible you over revved it changing down?

Cheers
Davie