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I'm looking for a 66mm piston with a 30mm compression height for a piston ported project I'm working on. Any recommendations for pistons without cutouts for reeds or boost ports?

A +2.0mm TS185ER oversize is 66mm, but ideally I'm looking for a 30mm comp height, rather than 32mm.

30mm comp height is a tough one, possibly look at muggello 200's I'm sure there's a 30mm (116 rod) version that may be suitable

Syd.......Have you considered using a 30mm CH windowed piston with a reedvalve inlet manifold?

webster used to weld up windows in reed pistons apparently.. I always thought this sounded a dodgy and a lot of hassle, but its a (maybe bad) option..

lofty wrote:webster used to weld up windows in reed pistons apparently.. I always thought this sounded a dodgy and a lot of hassle, but its a (maybe bad) option..

Sounds like a recipe for disaster to me!

I'd try AF, maybe something in the Wossner range as the 70mm comes without windows and they cut the window in for the RB kit.

The DT 175 piston had it's relevance prior to further knowledge becoming available. They seemed the only option available for Group Four engines & a good choice for HPC. Nowadays, with two stroke tuning, the lowering of primary compression has a more useful effect.

My preference with a long rod engine would be something like a 1 mm oversize Polaris piston & use a packer, but that's not the answer in this case.

I prefer to select pistons likely to be stronger than those intended for Lambrettas but am unaware of any that will suit this particular request.

However, there may be a NOS '175 to 200 conversion piston' available somewhere. I have an Ancillotti Dinamin NIB item as a museum piece (I guess!) but that is oversize(!) & is missing it's Dykes top ring.

dickie wrote:

lofty wrote:webster used to weld up windows in reed pistons apparently.. I always thought this sounded a dodgy and a lot of hassle, but its a (maybe bad) option..

Sounds like a recipe for disaster to me!

I had two piston`s done like this in the 80`s (cant remember why !) neither failed in use, both done by Taffspeed.

Look up grampian
They have loads of piston data on line.
Quite frustrating trying to compare though

Thanks for all suggestions! Much appreciated.

The 66 x 30mm Mugello looks ideal, except is has a boost port cut into it already (picture below). The Scuderia Lambretta Veloce kit has an option for a 30mm CH piston but as they're not widely available yet, I'm uncertain if it also has a boost port cut into it.

Running a reed manifold seems like added work and expense, particular as this will have very tame port timings.

I've also emailed AFR and they said to call. Wish me luck!

vegansydney wrote:Thanks for all suggestions! Much appreciated.

The 66 x 30mm Mugello looks ideal, except is has a boost port cut into it already (picture below). The Scuderia Lambretta Veloce kit has an option for a 30mm CH piston but as they're not widely available yet, I'm uncertain if it also has a boost port cut into it.

Running a reed manifold seems like added work and expense, particular as this will have very tame port timings.

I've also emailed AFR and they said to call. Wish me luck!

The window in the Mugello piston will not stop it from functioning in a bore that has no port, so that could be used.

I'm not sure why you wouldn't simply use a base packer with a piston of 39 mm compression height.......unless you think HPC is something worth having? Ha! Very obviously, I don't

As for reed valve manifolds, I'm not convinced of their worth, compared to, say, a well carburetted engine with adequate, well engined air filtration. On the other hand, a reed cylinder, with the porting designed to incorporate the reeds close to the bore (MQ springs to mind) is a different matter.

Still looking for a decent non-reed 66mm piston with a 30mm compression height. Any recommendations welcome.

So far I've found:

• Mugello 198cc has a 66mm x 30mm piston but it has small horizontal boost port
• The Scuderia Veloce has a 66mm x 30mm GOL piston option, but has a large boost port
• NOS '60s Asso 200cc TV175 pistons are hard to find, have very thick rings, and when found are usually in + oversizes
• AF Rayspeed don't make 66mm x 30mm non-reed piston
• all other 66mm x 30mm pistons I've found have windows pre-cut for reed valves: Imola, Monza etc..

As mentioned previously +2.0mm TS185ER oversize is 66mm, but ideally I'm looking for a 30mm comp height, rather than 32mm. Anything I've overlooked?

Thanks in advance!

I doubt anything exists with such a low compression height.

For 'completeness' the TS185 compression height is shown here as 32.5 mm:

https://www.mitaka.co.uk/ROAD_BIKE_PIST ... TS185P.htm

However, on the same sight, 33 mm:

https://www.mitaka.co.uk/CATALOGUE/PISTON_DIMS_ALL.htm

That said, I've used the oversize Wiseco TS 185 piston.

Unfortunately the Scooter Restorations own brand cast pistons seem to be unavailable.

The only other piston - that I have also used - is the Polaris Indy but the compression height is even more. They are available forged with one ring or cast with two rings. Good strong pistons though & can be 'found' cheaply.

Thanks, I'm a huge fan of the TS185ER pistons and have used them in a range of cylinders, most recently an RT195.

Unfortunately the cut ways on the 'ER' piston will be too close to the boost port on one of the cylinders I have. The non-'ER' piston requires a ring peg relocation--which I've had done (by a professional) in the past, but trying to avoid if possible.

The Mugello 198 piston should work for the other cylinder I have (no boost port) and in the meantime, I'll continue to explore alternatives.