Scooterotica

In the middle lane of the M62 on Friday going to Cleethorpes and having just overtaken I felt what I thought was a bit of a heat nip................ it wasn't!

Had a quick look before I called breakdown and found this



After a bit of swearing and phoning Beedspeed to see if they had a new cylinder I decided to get relayed to my mates house just outside Cleethorpes and fit the new kit on the Saturday morning.

Stripped the motor so I could clean out all of the bits of piston and found this



I could've cried!

So now to the biggie.............. can they be repaired?
Fella local to me (Barry Turner) uses a fella he reckons is the bollox with a TIG so is it viable or would I just be wasting my time?

Oh, just for the record, the piston was completely standard, not touched in anyway and was less than 12 months old. It hadn't seized and it was running sweet until it went. As far as I can see the piston just exploded???

Polini 207.

Yeah, they do that. Hone if the barrel is good or if damaged go oversize and get the newer style twin ring in the right size which seems to be almost bullet-proof.

Missed the bit aboutthe cases, give it a try.

And the piston isn't standard, it's a Polini 207 as I've already said.

Looked again, top ring welded into the seat which threw me, sorry.

Sorry, when I said the piston was completely standard I just meant I hadn't modded it in any way.
The top ring is stuck but not welded in, it's just pinched in from a bit of piston making it's way between the crown and cylinder head.
Barrel is in surprisingly good condition but I've got a new kit anyway to start from scratch, my only concern is the casings. If it comes to it I'll buy a new set but I've had the scoot since new and feel a bit misty eyed so I'd honestly prefer to have these repaired if it's viable.
Like I said this just happened completely out of the blue, no seize, no pinking no warning whatsoever so it's freaked me a little bit about the quality and strength of the Polini piston.

Cracks in the piston which lead to a failure such as this are often caused by incorrect piston / barrel tolerances. was the barrel worn? did you have any slap at low revs?
PM Al Diablo, I know hes a champion of this conversion and he might have a few ideas.

I think in total that the barrel has done roughly 6/7000 miles and the piston was less than 12 months old with only about 3500 on it so I don't think that tolerances were a problem?? Even Al has said in the past that he has his honed to give more clearance than standard.
Can't really say I heard any slap at all

I seriously doubt you'll be able to repair the casing without spending more than buying another set. You might be able to weld the pieces back in, but it'll be very difficult to get the crank housing to sealed again without machining which in turn would require excess material to be welded on before machining, and add to that a little distortion from the welding on both casing halves...

Cheapest set of casings I've been quoted is £200, SIP do a brand new set for £375 plus postage so if I can have these welded for around £50 it makes sense. As for distortion I thought it was minimal with Tig?
Had the damage been in a load bearing area I wouldn't have even contemplated a repair but I can't see crankcase pressure causing any problems to a welded repair. As for the machining I have a dremel, plenty of wet and dry and patience so hopefully all should be well.

:wtf: Sweet jesus, I hope you forgot a smiley at the end of that comment???