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Hi folks

Recently I trashed my piston on the C2c amongst other things. This is a cast iron top end 65mil plus bore. So my question is where is the best place to source a piston. It's a proper bitsa the bike a series three with a series two motor.

Any help would be appreciated.

Regards Cgt75b

Is it a modern 65mm to fit 107mm rod or 60s conversion 65mm designed for use with the TV 116mm rod?

Hello Adam

It's the latter pal.

I think you may have several options:

Suzuki TS185 pistons spring to mind but check out the compression height. Wiseco do them in Ø65 mm + if OEM are unavailable.

Otherwise, for the cost/hassle involved, you may be best to seek a piston that will fit your bore that is of a similar compression height to the Lambrettas that uses the shorter 107 mm rod.

Admittedly you would require a base packer (no bad thing IMO) & you might have to accept a single ring piston & even have to ‘cap’ the gudgeon pin, but there are advantages to a ‘modern’ piston in terms of strength & reliability.

I hope that all makes sense!

The TS185 piston has a compression height of 32.5mm. So, only 2.5 mil difference. 2.5 mil base packer should sort that out.
The Mitaka ones are good and sensibly priced.
Exhaust may need a little rework to fit properly.

Fast n Furious wrote:The TS185 piston has a compression height of 32.5mm. So, only 2.5 mil difference. 2.5 mil base packer should sort that out.
The Mitaka ones are good and sensibly priced.
Exhaust may need a little rework to fit properly.

Fast n Furious is spot on & re-reading my own advice I was possibly trying to offer you more options than you might like My apologies to both of you!

The Mitaka pistons are indeed very good, but original Suzuki would be my own preference. The only problem I have encountered with Mitaka is the gudgeon pin circlip retaining area breaking up on a TS250 piston. I've never had that with any of the many OEM Suzuki (PE, RM, TS) pistons that I've used. You might have to search long & hard for one, though they do come up on auction sites....

Thanks guys for your informed opinions gives some food for thought. I've taken the crank out today and there is a massive amount of side to side play on the rod which I think has contributed to my breakdown.

I may need to entrust it to an expert I think.

Thanks once again

Cgt75b

Still searching for the holy grail "reliability from a lambretta"

It's normal to have a lot of side to side on an unshimmed big end.

Did you have shims fitted on the small end?

rossclark wrote:It's normal to have a lot of side to side on an unshimmed big end.

Did you have shims fitted on the small end?

Just out of interest how much side to side play is normal?

No shims top or bottom.

If yours had an original TV crank fitted then it should actually be very little as the early cranks were aligned, although not shimmed, at the big-end. Later assemblies had lots of float at the big-end as the rods were aligned by spacers at the small-end. Most modern cranks have returned to alignment at the big-end but not do it by the introduction of shims.

All of the float info is detailed in most Lambretta manuals.

Adam

Thanks for all responses. Hopefully gonna get it fixed up shortly with a Gp crank with the long rod + new piston.