I stumbled on this website so I thought i would share.

Rotary valves

I find it wierd that they didnt include any bombardier designs.

--Biff

In trying to recall the rotary valves in dirt bikes, I know Kawasaki had some in the '70s as well, seems I recall the carbs actually inside the side cover!

I think the SWM had the bombardier motor, did it not? Quite the rig for its day! Same old Dellorto attached as many of todays bikes! Yikes! I think they got their moneys worth out of those castings!

In trying to recall the rotary valves in dirt bikes, I know Kawasaki had some in the '70s as well, seems I recall the carbs actually inside the side cover!

I think the SWM had the bombardier motor, did it not? Quite the rig for its day! Same old Dellorto attached as many of todays bikes! Yikes! I think they got their moneys worth out of those castings!

Mark,

Didn't the Aprilla have the rotary valve (disc) Rotax engine? In piston port engines (like most 2S Trials engines), the piston is the "valve" that opens and closes the ports, so the port timing is always symetrical (if it opens the port X degrees ATDC, it will always close the port at X degrees BTDC) but in the rotary, the disc has a cutaway that opens and closes the intake port, so that by changing the cutaways you can advance or retard the intake port timings on an individual basis. I once built a wacko roadracer using a Kawasaki 350 Bighorn single and had several discs with different profiles to tune the engine for the specific track we were running on.

Jon

different 'valves' though:

the two stroke disc valve controls inlet to the crankcase. It only has to seal a few psi, and always atmopheric temperatures hence little lube problems And the premix carries its own oilmist. Old Kawasaki discs were like masonite or bakelite material.

4 stroke is actually sealing the combustion chamber pressures and temperatures. hundreds of psi, hundreds of degrees.

Did engine research for my MS degree. Part of that was the literature searches. I got off on many totally unrelated but very interesting bunny trails about engine ideas through history. literally hundreds of spark plug patents, etc. WW2 era British piston engine war planes took the engine designs to the peak, especially given the low octane fuels, poorer lubes, and metallurgy. Amzaaing what was done, obsoleted by jets, but laid groundwork for much of the high performance engines of later and today. fascinating to me.

k

I think your both right. The swm and aprillia both had rotary valves.

--Biff

They werent made by Bombardier, they aere Rotax, All of the old Rotax Jetski engines (i build them for a living) had them.....crap idea

Ooops, just read the article, they are 4 stroke, well the 2 stroke ones have a plate on a gear driven from the crank, the plate spins and opens the intake at right moment of induction, instead of reed valves

I cannot recall all from years past, but a recent web search seems to reveal Rotax, Bombardier, Can-am and others all under one roof now, including Johnson/ Evanrude outboards for boats! Lots of shared technology there!

Aircraft, boats, motorcycles, snow, watercraft, quads!

Yeah, The company is now called 'BRP' (Bombardier Recreational Products) Rotax engines are still made in Austria under BRP... i was there in march this year

my friend had a 91 aprilia climber 280 and that had the rotax disc valve motor!!! powerful beast too!!!!

They werent made by Bombardier, they aere Rotax, All of the old Rotax Jetski engines (i build them for a living) had them.....crap idea

Maybe it was just the execution of the idea in the case of the Rotax jetski motors that was crap.

The most successful 250cc road race GP bikes in recent years (Aprilia) have rotary valve induction. They are noticably faster than their reed valve competitors (Honda and KTM).

In the case of bikes for Joe Public, yes they are a bit more complex than reed valves but do produce the goods. In twinshock trials the SWM with the rotary valve Rotax motor is a beaut and the SWM enduro bikes of the late 1970s with similar Rotax rotary valve motors were at the top of the performance tree at the time.

I cannot recall all from years past, but a recent web search seems to reveal Rotax, Bombardier, Can-am and others all under one roof now, including Johnson/ Evanrude outboards for boats! Lots of shared technology there!

The technology bubble floats all through the various companies. As I remember, around 1963, GM built a special 377ci smallblock, specially for factory supported Corvette racing, and the first of the aluminum blocks. As they didn't have the precise molding techniques for aluminum, they turned to Mercury Marine Products (outboards, I think the Stillwater plant in Oklahoma) to develop the proceedures as they had the right tools and technology. Then there's the Yamaha Ford SHO engine and so on and so forth. The crossover technology is amazing.

Jon

Edited December 19, 200718 yr by JSE

Then there's the Yamaha Ford SHO engine and so on and so forth. The crossover technology is amazing.

Jon

Ford has a Yamaha 4.4v8 currently in the volvo xc and s80 currently and I heard that they were pondering it for the mks in the future.

Great power plant. The sho was limited to 7200rpm not because of the engine but because the accessories on the belt would come appart.

--Biff

We just stick a HEMI in it and forget about it! No replacement for displacement!

Go get yourself that nice new 200 Gasser, Biff! It's sweet!

We just stick a HEMI in it and forget about it! No replacement for displacement!

Go get yourself that nice new 200 Gasser, Biff! It's sweet!

I am a power hungry fool. I love the 300 and dont know if i can go back.

Its silly that I tow said bikes with a miata... thats the yang to my ying.

--Biff