Small 47cc motorcycle block???


Local time
4:45 AM
Aug 25, 2008
heres the idea...are there any really small 4 stroke block? i mean like a miniature of a giant....

i was dreaming the other day with a miniature 6 cylinder engine...with something like a turbo cooller or something like


Active Member
Local time
6:45 AM
May 20, 2008
Central New Jersey, USA
There are lots of 50cc four stroke motorcycle and scooter engines out there, but because of their transmissions, they are too big for a motorized bike IMO.

If you were talking about a 50cc miniature 6 cylinder engine, I think such a creation would be a cool concept, but impractical because of the cost and complexity.


Well-Known Member
Local time
3:45 AM
Jul 3, 2008
Honda 50 cc RC116 from 1966
2 cylinder 4 valve per cylinder race motorcycle producing 16hp somewhere above 20,000rpm

Thats 25 cc per cylinder

Honda also made a 125cc motor which shared many parts. A 5 cylinder 125cc

A 50 cc 6 cylinder would be about 8 cc each
You try getting 4 valves or even 2 and a spark plug to fit a 8 cc cylinder

1966 RC116 is a new bore and stroke, now being 35.5 x 25.14 mm.

Power output is 16 bhp at 21,500 rpm. This means 320 bhp per litre and a Pme of nearly 16 kg/cm2 !
As regards bhp per litre, this is a figure that has never been surpassed by any naturally aspirated four stroke engine, and even today's formula 1 cars with their special fuel brews cannot hold a candle to it. I know this is not a totally fair comparison, but it gives an idea of the level of four stroke technology nearly 40 years ago.

This engine is the most advanced of all the Honda engines. Red line at 22,500 rpm. Carburettors have flat slides. The gearbox contains a nine speed cluster. Dry weight of the bike is 58 kg.
The piston pin has a diameter of 9 mm and weighs 6 g.
The inlet valve head is 13 mm, the exhaust valve head is 11.5 mm, and the stems are 3.5 mm diameter. Weight of the exhaust valve: 6 g.
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There are 4 cylinder boxer and inline engines available of between 50 & 100ccs.

There are 3 & 5 cylinder radials available of between 50-100ccs

There is one 14 cylinder radial engine and at least 2 V-12 model engines that would fit into a lengthened cycle frame. The 14 cyl radial is about 8HP on nitro fuel, It will, with a little fiddling, probably run petroil although power would be a little down.

there is a turbocharged/supercharged 6.09cui V8 engine built by Conley.

The problem with all of these is price - its high... 6000 Euros for the V-12. But the open valve gear and that sound... if I had the money it would be worth it.


ya, jemma mentioned the mini v-8 engine. search youtube for it. i have seen the video and the engine is fantastic!:D