SINGLE RING PISTONS

[STREETSLEEPER]

Can you still get single ring pistons for Lambrettas?
Here's a short story. In 1980 I bought a Jet 200 from a member of the 5:15s from Sevenoaks in Kent. The engine had had some tuning work done it, which appealed to me. The inlet and exhaust port were done well but the tuner had been too enthusiastic with the transfer ports. They were nicely shaped and almost semi-circular where they met the crankcase, so much so that they were wafer thin.
I was told the bike needed running in, but after treating it carefully it seized the first time I opened her up. Then again, and again. So I took the barrel to a local car engineering firm called Martin Storey for a rebore. They said that however many times they tried to hone the cylinder it kept flexing and clamping up; I needed a new barrel.
I got a new Italian barrel from a local motorcycle shop called Philpotts for £40. They said scooters were finished and they had just cut some brand new replacement frames in half to dump them! The engineers got hold of a piston for me which I think (not 100% sure) was an Asso. It had only one ring and was shorter on the inlet side. Does anyone recall one ring pistons? Can you still get hold of them?
I copied the porting on the barrel and it served me well for a good few years, ending up doing service on both my TV200s. The tale of the TV200s is another story altogether. It's one I shall get round to telling eventually because it demonstrates the good and the bad in scootering all at the same time
P.S. Sorry if I hijacked a thread by calumnal on SH/22s - still getting accustomed to using the forum.

[Knowledge]

In response to your question, may I pose another question? Why?

Some single ring Pistons were made available for scooters from the world of motorcross (piston transplants are very common, as few true performance Pistons were developed for Lambrettas until recently). Single ring Pistons were used in MX bikes where the service intervals were measured in (a few) hours, and blow-past on a single ring did not have a chance to develop.

Later, better two (thin) ring Pistons were developed which did the performance role as well as the single ring Pistons, but with much better durability.

Personally, I'd never use a single ring piston on a road going scoot.

[STREETSLEEPER]

Hi Knowledge. I found the following on an American two-stroke motocross forum:
Single ring vs. double ring pistons
One feller asks about pros and cons, and here's another's answer:
"Question is why wouldn't you run a single ring, there is NO benefit in a twin ring in a race bike."
Admittedly most Lambrettas aren't raced. Mine was. In fact the single ring piston lasted no less than 10.000 miles which included time on the track. It was still in that same barrel, unseized and undamaged, when the TV200 it was fitted to passed out of my hands.
A great many Lambrettas on the roads nowadays are highly tuned Any 200cc bike that puts out 15bhp is about 50% more powerful than standard. Imagine uprating any motorcycle engine to put out 50% more power, well that's a massive increase in power! Therefore fitting the very best parts, including "racing" pistons makes sense. Motocrossers rave about their Wossner single ring pistons, and rightly so. Let's consider these racer's pros and cons (we can agree or disagree to these).
Heat dissipation – some say it is better with two rings, others that a single piston ring improves cooling due to lower friction.
Less friction equals more power.
A single ring leaves less to go wrong.
A single ring makes the piston less stable (apparently).
A single ring piston weighs less than a double ring piston (marginally).
A single ring engine will rev higher with less stress on the piston, gudgeon pin, small end bearing, rod, big end bearing, crank pin, and main bearings.
Loss of compression (noticeable?)
Shorter life span.
The single ring piston in my old cast iron barrel did all it was asked to do and more, therefore, from a personal point of view (and that's all it is), I would go with the single ring piston if I had the choice, quite simply because it was the best piston I have ever fitted to a Lambretta. It is the only one that served me from day one without a hiccup, and originally I didn't fit it with longevity in mind. Only I'm not sure if one can still get hold of them for standard barrels or even for any of the tuned barrels in kit form?
I'm not arguing with you. You're not called Knowledge for nothing. I don't profess to be an expert on Lambrettas or even slightly knowledgeable. I am an auto engineer by trade however (so not entirely ignorant) and love discussion, even if it's controversial!

[Scooterlam]

Why don't you run a 2 ring piston with just one ring,

Sorted

[STREETSLEEPER]

Why don't you run a 2 ring piston with just one ring,

Sorted

Good idea scooterlam!
I've done it when I had to. It's a good "get you home remedy". But seriously, does anyone know of a single ring piston that's available, or does anyone have one fitted?
Looking on the lighter side I just found this picture of my mates chopper "Illusion". He had it in his bedroom for nearly 30 years and is doing it up again.

https://encrypted-tbn0.gstatic.com/imag ... WbfuuQPwsI

[Scooterlam]

Seriously,

What is the difference. a single ring piston is just that take a ring out of a two ring piston and you have a single ring piston.
Extra grove will act like an oiler ring on a four stroke. Ive always run 3 ring pistons with just two rings no issues.

I've an original MB DJ if your mates after one.

[hullygully]

AF's sell wossner single ring pistons that are coated

[nickw]

Streetsleeper, is that Steve? I've not seen him for years. If it is the same chap didn't he have Scootique in Crowborough? I used to go to his shop mid eighties which is where I met him. History wise didn't he work for a custom outfit at one time called Taylor's and didn't illusion have the longest wheel base of any Lambretta at the time. I can remember trying to move it in his shop and it would take forever because of its length. Memories, eh!

[Eden]

im running my new GT250 with just one ring. chose to for two reasons....

one ring = less friction so less heat while running the barrel in and im using an old used ring, the two new ones will go in when the top end is run in