I f***in hate scooters!!!!!!!!!!!!!
The repair can be welded but the casings would have to be machined , it aint a repair that a dremel can sort imho , i would bite the bullet and replace
Tig welding will cause distortion, however with a bit of carefull filing you will be able to sort it out.
when you have filed the case halfs till they are nearly right, put some coloured chalk on one side and bring the 2 parts together, split them again, the chalk will transfer from one side to the other only where they touch,
this will indicate where you need to do a little more filing \ grinding.
you could use engineers blue (it`s like blue vasaline but it can be messy) but chalk is cheaper.
gaskets are used on engines to seal small imperfections so with a bit of patiance you will sort it out.
Dont many of the top tuners weld their engine cases around the transferes prior to porting or around the crank area prior to stroking their engines
when you have filed the case halfs till they are nearly right, put some coloured chalk on one side and bring the 2 parts together, split them again, the chalk will transfer from one side to the other only where they touch,
this will indicate where you need to do a little more filing \ grinding.
you could use engineers blue (it`s like blue vasaline but it can be messy) but chalk is cheaper.
gaskets are used on engines to seal small imperfections so with a bit of patiance you will sort it out.
Dont many of the top tuners weld their engine cases around the transferes prior to porting or around the crank area prior to stroking their engines
It`s all powerfull white mans magic
My Scoots,
http://i897.photobucket.com/albums/ac17 ... CF0600.jpg
http://i897.photobucket.com/albums/ac17 ... 01/035.jpg
My Scoots,
http://i897.photobucket.com/albums/ac17 ... CF0600.jpg
http://i897.photobucket.com/albums/ac17 ... 01/035.jpg
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joeythescooterboy
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At last a voice of optimism 
Nemo saltat sorbius, nisi infanus est.
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sean brady scooters
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forget it matey ,get S/H cases or new .
Sean Brady Scooters - 01765 690 698
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joeythescooterboy
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Oh Bugger! 
Nemo saltat sorbius, nisi infanus est.
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Boz
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Years ago (88) my P200 spat it's little end bearing round the crank mouth area.....damage was not as bad as yours, but the general opinion of MSC & other demi-experts was a new set of casings...for peace of mind really....Thankfully however a spare complete 200 motor out of a wrote off P2 was aquired for a very reasonable £50 ! (was 88 though).....Just my opinion, but new casings = zero risk.....repaired casings = medium / high risk (depending upon skill of welder / mechanic)...suppose it's your decision though at the end of the day fella !
OK wouldn't do this on a customers bike but would definitely do it on one of my own bikes.
There is a lot more drive side P2 casings shot than flywheel sides. It shouldn't be too hard to find another flywheel side. Put a search in on ebay for used PX casings. Casings that need work often go for pennies and its mostly the drive side thats damaged. There should be loads of disc ones like yours due to gearbox let goes on the later engines.
I've used miss matched casings many times but would advise at least trying to find one from a similar year ie don't use a mk1 case on an EFL motor. Dry assemble it with the crank bearings and crank in but no seals. Do the casings up with a dry gasket and turn the crank over feeling for any friction. Check the cylinder gasket face for a match as well. If this all checks out fit the gearbox and primary and check all is well there as well.
Its infinitely easier repair than welding the casing.Its delicate work and unless you have a s**t hot welder as a mate it could end up costing a lot more.
Regards the piston I am surprised its happened with the newer 2 ring type. Whats happened is why nobody used Polinis for years because the earlier pistons did exactly that without warning.
There does seem to be nip marks on the piston though which might have of ocurred before the let go. They look like seizes around the studs and with the rings smeared as well means the seize happened first and then the piston detonated. What piston to bore clearance did you have? They must be honed to at least .004". Also a low comp head.
Mine runs a .005" clearance because it was put on Readspeeds dyno from new when the original single ring GS piston came out to test for Scootering. That piston stayed in for a season then changed for the polini 2 ring piston which stayed in for at least 10,000 miles and was only changed to test the SIP GS piston I'm on the same bore still after 5 years and just replace rings every 3-4000 miles. It does rattle a little on tickover but it has never siezed and still starts first kick even when warm.
What it does show is that the polini piston still has weakness when seized. At least its a rebore and not a replate as with a malossi. The GS piston is a better piston than the polini so would recommend the extra cost.
I'm just glad your here to post about it because a let go like that on the motorway could easily be fatal.
There is a lot more drive side P2 casings shot than flywheel sides. It shouldn't be too hard to find another flywheel side. Put a search in on ebay for used PX casings. Casings that need work often go for pennies and its mostly the drive side thats damaged. There should be loads of disc ones like yours due to gearbox let goes on the later engines.
I've used miss matched casings many times but would advise at least trying to find one from a similar year ie don't use a mk1 case on an EFL motor. Dry assemble it with the crank bearings and crank in but no seals. Do the casings up with a dry gasket and turn the crank over feeling for any friction. Check the cylinder gasket face for a match as well. If this all checks out fit the gearbox and primary and check all is well there as well.
Its infinitely easier repair than welding the casing.Its delicate work and unless you have a s**t hot welder as a mate it could end up costing a lot more.
Regards the piston I am surprised its happened with the newer 2 ring type. Whats happened is why nobody used Polinis for years because the earlier pistons did exactly that without warning.
There does seem to be nip marks on the piston though which might have of ocurred before the let go. They look like seizes around the studs and with the rings smeared as well means the seize happened first and then the piston detonated. What piston to bore clearance did you have? They must be honed to at least .004". Also a low comp head.
Mine runs a .005" clearance because it was put on Readspeeds dyno from new when the original single ring GS piston came out to test for Scootering. That piston stayed in for a season then changed for the polini 2 ring piston which stayed in for at least 10,000 miles and was only changed to test the SIP GS piston I'm on the same bore still after 5 years and just replace rings every 3-4000 miles. It does rattle a little on tickover but it has never siezed and still starts first kick even when warm.
What it does show is that the polini piston still has weakness when seized. At least its a rebore and not a replate as with a malossi. The GS piston is a better piston than the polini so would recommend the extra cost.
I'm just glad your here to post about it because a let go like that on the motorway could easily be fatal.
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joeythescooterboy
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Al, believe me kid there weren't just skid marks on the M62!
looking at the piston in front of me the marks are from stray bits of piston not seize marks, I wish they were at least then I could say I'd overcooked it and have a reason for the failure but I had the motor apart only a couple of weeks ago to renew all bearings and seals and then checked the rings last week in prep for Cleethorpes and all was well, not a scratch.
All the way to Birch services on the M62 I was doing about 55/60 (GPS) and it was fine, I even checked me plug while we were having a coffee and it was luvverly jubberly, filled up did another 4 maybe 5 miles towards jct 21 and it just locked up, no warning like when you have a nip, it just locked solid in the middle lane at 60.
The barrel is still fine, no seize marks whatsoever, just a few chips on the exhaust port from the ragged piston so I just can't fathom why it happened. I'd even retarded me timing and upjetted to a 135 and raised the needle (AV264) as I was taking the wife on the back because I wanted everything as safe as.
Had I been thrashing her I'd understand, but I wasn't. Had the barrel and piston done excessive miles I'd understand but the barrel's done about 7000 and half of that was with a new 2 ring piston so I don't think that to be excessive?
Had the Father in law round today (scientist,) and the first thing he said when he saw the piston was "metal fatigue, classic signs because can you see just here................" at which point he lost me with science............ my point is that I honestly can't think of anything else other than the piston just letting go.
Anyway, back to the casings.
A good mate, Will, (of PEP Parts engine fame,) has just sold me a set of casings for a very reasonable price, and I've just done more or less what you suggested with the flywheel half and all seems well, so soon, thanks to Will, I'll be back on the road with a brand new Polini top end which will give me time to have my old casings repaired. I know it may sound as though I'm a bit of a fanny but I bought the scoot new in '99 and I love her to bits, we've had some cracking times, so if they can be repaired that's what I want to do!
If I have to spend the next 6 months in the garage with me dremel and some fine wet n dry then that's what I'll do but I want my baby back together.
looking at the piston in front of me the marks are from stray bits of piston not seize marks, I wish they were at least then I could say I'd overcooked it and have a reason for the failure but I had the motor apart only a couple of weeks ago to renew all bearings and seals and then checked the rings last week in prep for Cleethorpes and all was well, not a scratch.
All the way to Birch services on the M62 I was doing about 55/60 (GPS) and it was fine, I even checked me plug while we were having a coffee and it was luvverly jubberly, filled up did another 4 maybe 5 miles towards jct 21 and it just locked up, no warning like when you have a nip, it just locked solid in the middle lane at 60.
The barrel is still fine, no seize marks whatsoever, just a few chips on the exhaust port from the ragged piston so I just can't fathom why it happened. I'd even retarded me timing and upjetted to a 135 and raised the needle (AV264) as I was taking the wife on the back because I wanted everything as safe as.
Had I been thrashing her I'd understand, but I wasn't. Had the barrel and piston done excessive miles I'd understand but the barrel's done about 7000 and half of that was with a new 2 ring piston so I don't think that to be excessive?
Had the Father in law round today (scientist,) and the first thing he said when he saw the piston was "metal fatigue, classic signs because can you see just here................" at which point he lost me with science............ my point is that I honestly can't think of anything else other than the piston just letting go.
Anyway, back to the casings.
A good mate, Will, (of PEP Parts engine fame,) has just sold me a set of casings for a very reasonable price, and I've just done more or less what you suggested with the flywheel half and all seems well, so soon, thanks to Will, I'll be back on the road with a brand new Polini top end which will give me time to have my old casings repaired. I know it may sound as though I'm a bit of a fanny but I bought the scoot new in '99 and I love her to bits, we've had some cracking times, so if they can be repaired that's what I want to do!
If I have to spend the next 6 months in the garage with me dremel and some fine wet n dry then that's what I'll do but I want my baby back together.
Nemo saltat sorbius, nisi infanus est.