Question: Why was the biggest two-stroke bike 500cc?

[Pedrostt500]

Yamaha had the TZ 750, though it wasnt realy a production bike, the big 2 stroke were killed off when the USA brought in emmisions controlls in the 70s with the catilitic converters, fitted to their cars.

[Motu]

Anyone know the answer to this one:

Why were two-stroke motorcycles never bigger than 500cc?

Or did a manufacturer try making one bigger? It's something I've always wondered?

Would the power-to-weight advantage be diminished at larger sizes, or would they use too much oil?

Total capacity or cyl capacity?.Plenty of 750cc total capacity as posted by others.But 500cc is pretty well the limit for cyl capacity....I think the KTM 550cc would be about the biggest I've heard of....at least production bikes anyway.2 stroke diesels have some pretty huge cyls - marine diesels are nearly always 2 strokes.

[rogson]

As I alluded to earlier Maico made a 760cc 2-stroke air-cooled single a while back, and make a 685 2-stroke single now.

http://www.maicouk.co.uk/html/supermoto.html

[MVnut]

Seem to remember a kawasaki 750 triple that screamed. In fact at the time of its release one was expected to remove ones brain before attempting to ride this machine.

Only the frontal lobe

Kawasaki 750 triple 'widow maker'.
My old man got to ride one once, scared the shits out of him!
That bike was the fasting thing on the road at the time and had drum brakes front and rear crap handling too!

Disc brake front on all H2s..... what's wrong with the handling....you ever ridden one ??

[Motu]

As I alluded to earlier Maico made a 760cc 2-stroke air-cooled single a while back, and make a 685 2-stroke single now.

http://www.maicouk.co.uk/html/supermoto.html

Sorry - I saw your post but chose to ignore it for reasons I refuse to disclose....

[pete376403]

It was more of a braaaack-ring-ding-ding-clatter-roooar sort of noise. It's remarkable how much mechanical noise a big, air-cooled, two-stroke can make with so few moving parts.

Most of the noise was air cooling fins ringing like bells. Hence the move to water cooling. Also space limitations - each air cooled cylinder needed about 50mm worth of fins around the barrel, but water cooled barrels could be much closer together. Add a big dollop of air induction noise (carburettors)Finally add the noise transferring through the sides of the expansion chambers (regardless of the amount of muffling at the chamber outlet) and you've got a pretty rackety package, albeit a fast, rackety package.

I really miss my old (air cooled, noisy) IT400

[TLDV8]

[TLDV8]

These are Kawasaki H2's (late 1971/1972),not to be confused with Kawasaki H2A's (1973) or H2B's (1974) or H2C's (1975)

fwiw



This was fairly standard though. (Redline was a fairly low 6800 rpm) but never let the truth get in the way of a good story.
Of course porting,34mm carbs and a good set of pipes was another thing. (90 hp perhaps back then,over 100 is not hard these days.)



At the time there was probably little need to increase the capacity (The H2 engine will bore to 780cc) but being aircooled the piston clearance was fairly big without increasing the (71mm) bore size further.

Seem to remember a kawasaki 750 triple that screamed. In fact at the time of its release one was expected to remove ones brain before attempting to ride this machine.

The 1969 Kawasaki H1 500 had the biggest rep like that but only because of the sudden HP increase around 6000rpm

[nudedaytona]

Can anyone tell me what porting means? Something to do with the cylinder heads?

[TLDV8]

Can anyone tell me what porting means? Something to do with the cylinder heads?

Two stroke's have passages in the cylinder wall (ports),the fuel mixture goes from the crank cases to the combustion chamber via the intake ports when the piston travels down.
Altering the height etc changes the timing (like a modified cam in a four stroke)
Go to crazy with the porting and the power band becomes very narrow.

[banditrider]

Old Motorscrapers have 2 stroke V12 twin turbo, twin supercharged diesel engines (aboot 12l I think). They don't go that fast but with open pipes make a 500GP bike sound pretty gutless!

Then there's these: http://people.bath.ac.uk/ccsshb/12cyl/

Had a look at an 8 cyclinder marine diesel once: twin turbo-charged 2-stroke diesel, a think it was 24,000hp at 150rpm. Bore was 900mm and stroke was 1800mm. Turbos were fan assisted. Only a tidler...

Boat was a small container boat and it had 2 of them that got it to 23 knots. it also had at least 6 (maybe 8) smaller 8 cylinder diesels of 1,200hp for generating onboard power for reefers and what not.

[pete376403]

When I was at IBM I got asked to service a data logger printer on a container ship. The logger was down in the engine room. The engine in that boat was a dirty big nine cylinder, the crank had a flexible coupling between the fourth and fifth cylinder, to allow for the boat hull flexing in heavy seas. I also recall seeing a spare turbocharger strapped alongside one of the bulkheads, the exhaust scroll would have been about two metres in diameter.
But think the OP was about two stroke BIKE engines, so maybe this doesn't count.

[Coyote]

Multis don't count - here's the granddaddy
http://http://www.superhunky.com/nov00rsMaico760.html

Dead link. But yes, the Maico is badass.

The new one must be even better with newer technology behind it. It's so good, the Americans are taking it and putting their own brand on it!
http://www.motorbikes.be/en/ATK/2004/700%20Intimidator/

[Coyote]

Sorry - I saw your post but chose to ignore it for reasons I refuse to disclose....

Go on

10 characters

[nudedaytona]

Two stroke's have passages in the cylinder wall (ports),the fuel mixture goes from the crank cases to the combustion chamber via the intake ports when the piston travels down.
Altering the height etc changes the timing (like a modified cam in a four stroke)
Go to crazy with the porting and the power band becomes very narrow.

I don't recall seeing any holes like that in the cylinder I recently took off.

The only hole I can remember seeing was the exhaust hole. There were holes in the cylinder head, but they seemed to be for coolant to flow around on the outside of the cylinder.