Scooterotica

bought a piston on ebay, listed as a TS185 piston, its diameter at the crown is 63,6mm, 75mm long and inside is marked made in japan 29900, but the gudgeon pin size is the same as a standard lambretta, which ive been told means it cant be a suzuki ts 185 piston as they have an 18mm gudgeon pin. comparing it to a standard TV175 piston it is aprox 1mm shorter in the skirt but apart from the crown being a different shape its roughly the same size
a/ does this sound like a ts 185 piston
b/ why do i need a 3mm packer when it looks to fit just fine

TS185 have 16mm gudgeon pin size (standard Lambretta), whereas the TS250 piston (used for Suzuki 225 conversions) has 18mm.

There's two ways of doing this conversion -one is machine the barrel down so you can use standard 107 conrod cut piston down revy setup.Or the the other 110 rod standard piston I think you still need a packer but can't can't remember how much in mm - bit more torque than other setup.

Or the third way
116 tv rod or 115 rd400 rod and keep near std port timings if required and no barrel mods

It's a TV so 116 rod but does it need packer?

Done one with a tv rod and it needed a 2mm packer

Assemble it without the base gasket and see how far the piston sticks out the top of the barrel, that'll tell you what packer you need.

A TS 185 piston has a 32mm crown hight . A std Lambretta has a 39mm crown hight ! So to use a 107 rod you need to remove 7mm !
That's if everything is as it should be . I'v known cases to be out by over 3mm . The problem when using a 107 rod is the inlet port
and how low the inlet is when you have removed the metal required . You could end up heading towards 170 degrees of inlet which
is a tad on the high side for on the road . I would be looking for 150-155 on the inlet . 125 on the transfers and 185 on the exhaust !
That's only my opinion and other folks that tickle two strokes may have differing ideas !