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S2 Stock 125 Piston skirt or no skirt ?
Posted: Tue Jul 10, 2012 2:00 pm
by Rotor
Just replaced the siezed piston on my 1960 S2 but the 'new' piston has a skirt where as the old one does not, will this perform ok, beter worse clearing the ports? or is this just the wrong part alltogether
P.
Re: S2 Stock 125 Piston skirt or no skirt ?
Posted: Tue Jul 10, 2012 2:03 pm
by Adam_Winstone
Leave the skirt. You will not notice any performance gain if you remove it but you are far more likely to have cracks develop from the corners of the transfer windows (near gudgeon pin boss) if you do remove them. As such, little to be gained by removing the bridges BUT a lot to risk if you do!
Adam
Re: S2 Stock 125 Piston skirt or no skirt ?
Posted: Tue Jul 10, 2012 2:07 pm
by Rotor
Thanks for the quick reply, so would that mean the old piston would of had the skirt removed by an earlier owner, or do they vary by make and brand ? sorry for the newbie questions..
P.
Re: S2 Stock 125 Piston skirt or no skirt ?
Posted: Tue Jul 10, 2012 6:44 pm
by Adam_Winstone
^... it is more likely that it was a replacement piston that was in there as the later models (Series III) didn't have the bridge across the windows. Many 60s tuning texts suggest that removing the bridge is a good thin but that doesn't take into account that the later pistons (without window bridge) were cast intentionally to not have a bridge so are stronger around the windows and have larger radii... both of which reduce the chance of cracking. To simply cut the bridges out of an early piston leaves you with a weak piston that was not designed to be used without the support offered by the bridges and begs for trouble.
As a newbie I read the old texts, cut the window bridges out and then suffered piston cracking
You are best off leaving it as Innocenti designed.
Adam
PS - The only time that I'd start telling you to upgrade your piston is if any tuning work has been done to the original barrel, especially tuning to the exhaust port. As a newbie I'd suggest you leave it as standard for now as tuning introduces cost and problems, unless you know what you're doing.
Re: S2 Stock 125 Piston skirt or no skirt ?
Posted: Wed Jul 11, 2012 2:03 pm
by Rotor
Thanks all makes sence now, the Piston that was in the engine was a 2nd oversize, and the new piston Ive replaced it with is just an equivalent but different make then, no thoughts of tuning at present just want to get the scooter reg'ed and on the road before winter then early next year put a kit on and go from there really !
Thanks
Paul