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I'm not 100% sure, but I think it was a combination induction - piston port, with no reed valve control to that circuit, but a case reed valve, like the early RM250 /370s. Or, a full case reed induction - as I said, I'm not 100% sure - But I Am 100% sure it was Not a Disc valve induction engine. That was on the up to 250 / 280(?) Rotax bike engines, only. It was a great engine though - An ATK 406, is on my list of bikes I'd love to get into my garage, one day.
Reeds are simple = very much part of the whole 2t 'ethos'. Older blokes here will remember the mind boggling change in engineering direction, when Honda gave up on their NR500 = 4T, 8 valved (yup 32 in total), Oval pistoned, double con rod engine (effectively a V8, that got past the 4 cylinder rules - REVs, Baby - it what modern 4ts [still] need), to the incredibly simple, 3 cylinder, reed valved 2t Triple, that they got their first modern era 500 Road Race title on.
Disc valves - far more involved - not so simple, and far more expensive than simple reed valves. But, if a DFI set up, that ran a high pressure system (not really needed, as there are So Many variations on DFI, not just the in head, High Pressure systems developed by Orbital Engineering in OZ, and used by so many manufactirers in Car and Truck DFI / stratified injection systems) was used on a 2t - that set up pictured on the CZ, and the far , far more modern system that was used on the 125 Aprilias - the shafts used for the drive of the disc valve, could double / triple etc up for pressue pump usage and other 'drives'. Sorry about the length of that sentence/ paragraph - I suck at grammar.
But, it - High Pressure DFI - probably won't happen. Far simpler 'clean' set ups exist for 2ts, and we'll see them when the Euro emissions, coming in 2017 are applied to 2ts that need to be road registered. A lot of markets, need bikes to be road registered / licensed, for any real sales to be had.
2) The Maico 125 probably killed any interest. I hear a Rupp could outrun it.
The Shop
DeCal Works Huge Plastic Inventory of UFO and Polisport kits.
Luxon 4-Post Bar Mounts
$189.95 - $239.95
look whats possible though if applied.
1. Take a conventional overhead 4t and take out the valves, valve springs and rocker arms.
2. Move the cams as close to the combustion chamber as possible.
3. Make the cams a solid cylinder, ie no lobes
4. Drill holes perpendicular to the cam shaft at the proper orientation to form intake and exhaust ports/valves
As the the "cams" rotate, the holes open and close into the combustion chamber. So the design is like a hybrid 4t and rotary valve/variable exhaust port 2t.
Theoretically, it should be simpler, lighter, less inertia, less friction,more balanced than a 4 t, but probably has worse emissions.
Never heard why they didnt continue the development.
Crushedankle@yahoo.com
Thanks
And Bearuno = good stuff, as usual !
Did a search , loads of info on it , but the original website is a dead link ..
The Bombardier/Rotax designed engine was a deceivingly FAST ROCKETSHIP for its time in 1978. It also had a Supertrapp style muffler and the exhaust would exit out the side through disks that you could vary to adjust power. This made it ultra quiet and you could sneak up and pass people before they knew what hit them.
This was pre-powervalve days and the Big 4 bikes were wheel spinning, swapping, hard hitting, obnoxiously loud beasts who couldn't hang with the ultra smooth, put power to the ground Rotax engine.
I had the only Can-Am on this packed gate in a CMC Carlsbad/Saddleback series and holeshot the majority of the motos. It was pretty cool to have the only Orange machine as people would check it out in staging.
By the end of the six week series I was not alone.
That bike helped me win a brand new XR 75 and will always hold a special place in my moto-heart.
That is Juan Benevidez in the blue helmet on the Yamaswap who would later get a Factory Can-Am ride.
Looks to me if the rotary window is on the crank it feeds that bearing well but could starve the other crank bearing of oil and also starve the transfer ports on the opposite side.
Does the crank have a window also in the weight? I've never seen inside one.
The valve running off a spur gear is better for balance of lubrication but looks like a lot of parasitic drag and flywheel effect there.
And,performance of a 2str is all about having as little volume below the piston as possible so when it is on down stroke all the fuel mixture gets shoved thru the transfer ports.
Well, the runner. Have a half a basement full of Can-Am projects. Hope I make it to retirement in one piece so I can really get into them.
Trying to keep my tongue out of the spokes:
Pit Row
Honda, have probably done / experimented with and patented up to the eyeballs, every sort of ICE (and a zillion other techs) there has ever been. Just search for 2t Honda patents and you'll be stunned - if you think they are a solely 4t company.
The Rotary Valve 4 stroke induction, is somewhat of a 'holy grail'. It's been around for a long, long time. Read Phil Irvings ( an OZ Engineer, most famous for the Vincent V Twins) Autobiography, and you'll see one of his first jobs , in the early part of last century, was working at an Australian Engineering firm that Made Overhead Rotary Valve engines - large industrial ones.
It's been seen as a way to get over poppet valve limitations, but heat / sealing issues have been the bane of it's implementation. An Australian engineering duo, had a reasonably successful rotary valve top end on a XT / TT engine, that got a fair bit of coverage, but the heat / sealing issues, were still a major problem.
So many engineering solutions out there, it's amazing to read up on them.
Coates Spherical Rotary Valve
Bishop Rotary Valve Engine
Comparison of Standard and Rotary Valve
History of Rotary Valve Internal Combustion Engines
F1 Discussion Forum Thread
Reed valve= very close to disc valve peak potential but in sync with motor over a very long rev range.
http://www.amazon.com/Design-Simulation-Two-Stroke-Engines-Gordon/dp/15…
Best book ever written on 2 strokes...
That KS125 was especially low powered. I do remember being sad when the speedometer quit working with 19,000 miles on it. I rode it for years after that. I believe ngk sparkplug stock went down after I got rid of that bike. A plus was good for two weeks, then gone. No energy from the worn points, I think.
Never had the top end off and gave the bike away in running condition.
Short life expectancy on the cranks ,though. A lot of them puked within the first 2-3 hours of run time.
My older brother had five of them during the 70-71 era. Had to bring at least two to each race to be safe.
Sprockets Park TT, Bakersfield , California 1970, 100 junior class.
Holeshotting the 200 expert class on an F-7 175 rotary valve Kawasaki, Porterville Spinners, California, 1972.
Suzuki 100cc rotary valver ,Bill Johnson #1, my brother on the #23 Greenstreak, Sprockets Park ,1971, 100 expert class.
You make a good point about the crank bearing as I did have one go out early on.
Here is pic of the parts breakdown. I thought about cutting the pie plate more but never did.
The gas girlings were junk and after they seized up I went down to Kolbe Honda which was the hot ticket for Can Am's (they ended up with the race team) and purchased some Fox air shocks and air caps for the Marzocchi forks and I was good to go.
Those are the only mods I did to that bike.
The simpler design and broader power band of the reed valves is why we don't see the rotary valved engines any more. Even if you break a reed (as long as it's not steel) no engine damage but if you broke a rotary valve, the engine was done. I don't remember any fiber rotary valves although some one must have tried it.
Post a reply to: Why isn't the rotary valve two-stroke used by anybody still making 2 strokes?