Short Stroke 750 Info
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lcrken
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I've tried to get an answer to that question. Some years ago I got answers ranging from "I know they did. I saw one in ..... dealership." to "No. The only one they built was the one for display at the .....show." In any case, if they sold any, there certainly weren't many. The only Commando production bikes I've ever heard of with short stroke 750 engines were ones where the dealer or owner replaced the original engine with the short stroke engine. I've been hoping someone on the list with closer connections to the factory could provide a better answer.
Don't know about the 80 hp at the crank, but I think those might be pretty small horses.
Ken
Don't know about the 80 hp at the crank, but I think those might be pretty small horses.
Ken
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This question would be a good one to pose to Brian Slark.
As for the 80 hp at the crank (est. 72 RWHP) sounds reasonably in the ball park with proper pipes and tuning.
As for the 80 hp at the crank (est. 72 RWHP) sounds reasonably in the ball park with proper pipes and tuning.
grandpaul
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The write-up at the top, with ILLUSTRATIONS, is interesting.
"Illustrated" and "pictured" are two different things, and "illustrated" was used carefully, AND italicised. In other words, that is NOT a PICTURE of a Roadster with an actual short stroke engine in it, but merely an ILLUSTRATION of what it SHOULD look like if/when produced.
"Illustrated" and "pictured" are two different things, and "illustrated" was used carefully, AND italicised. In other words, that is NOT a PICTURE of a Roadster with an actual short stroke engine in it, but merely an ILLUSTRATION of what it SHOULD look like if/when produced.
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No bikes were ever built with the shortstroke engines bar the handful of "TX750" Racers.
There was a quantity of fully built shortstroke engines and certainly a cache of parts which, I believe, all ended up with Rhind-Tudd of WASP fame. He took most engines apart and used the parts that were identical with normal 850 engines to build those. Some bits, and certainly built and part-built TX750 bikes or TX750 chassis ended up with Gus Kuhn and were sold off from there. I have a photograph of Frank Perris and Vincent Davey sitting on TX750s side by side in some back yard (Gus Kuhn's?).
There was even a part number issued by Nortons to rebuild a 750 short stroke into a standard 850 engine.
The polished cylinder head was wishful thinking. The few shortstroke heads I encountered were unpolished.
There was a quantity of fully built shortstroke engines and certainly a cache of parts which, I believe, all ended up with Rhind-Tudd of WASP fame. He took most engines apart and used the parts that were identical with normal 850 engines to build those. Some bits, and certainly built and part-built TX750 bikes or TX750 chassis ended up with Gus Kuhn and were sold off from there. I have a photograph of Frank Perris and Vincent Davey sitting on TX750s side by side in some back yard (Gus Kuhn's?).
There was even a part number issued by Nortons to rebuild a 750 short stroke into a standard 850 engine.
The polished cylinder head was wishful thinking. The few shortstroke heads I encountered were unpolished.
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jaydee75 said:
745.3 cc going by the 77 x 80 posted.
It was still a long stroke engine with a piston speed over 4000 ft/minute at the quoted 8000 rpm.
Ducati round case 750's of the same period (1971 to 1974) were 80 x 74.4 as was the 1975 750 SS Desmo square case road bike.
A case with Norton using what was available with available engine castings ?
A Norton 750 at that time with bore and stroke closer to the Ducati with a new cylinder head with wider bore spacing and cases to match might have been another story.
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Yeah, 80 hp at the rear wheel would be more like a home run. If you go by the configuration of the brochure shown at the top of this page I would take a swag at 65 RWHP.......maybe.
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I cannot see the sense in an 80mm stroke commando engine. An 81mm stroke Triumph engine would have to be better because of the separate cams for inlet and exhaust. However they barely cop 8,000 RPM reliably. I seem to remember that one 650 Triumph twin in the 80s had a 75mm stroke. The trouble with using that crank would be in getting the bores big enough to get the full 750cc - too close together in most British twins. And the piston weight might be too high. I often think the G45 Matchless should have been developed much more than it was. Some of the guys these days are building Matchless twins with staggered Yamaha XS2 cranks. I suggest the way Norton should have gone would have been to build a 750cc short stroke four valves per cylinder DOHC Paton engine, with seven speeds in a cassette. It could still be done - but why ? - No race class , and who would want it on the street ?
That 80 BHP at the crank is much the same as the H1 Kawasaki, however the torque would be different. The bike might not stall in a head wind, and actually be more rideable ?
That 80 BHP at the crank is much the same as the H1 Kawasaki, however the torque would be different. The bike might not stall in a head wind, and actually be more rideable ?
acotrel said:
I've got an older bike thats barely got more than 10 hp, and its quite rideable.
On the road. Although it will probably never win any races.
But road riding isn't about winning anything, its about getting there and enjoying the ride...
Remember too, 10hp is theoretically enough to get you to 60 mph - as long as you haven't overdone it on the crisps.
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Speed is only relative. I believe that a dead stop from about 26 KPH will usually kill. If you are riding an old 16H Norton, and everyone around you is on similar, everything is lovely until someone makes a daring passing move. Then we right back to thinking about MotoGP or the IOMTT. I use to ride an old exWD 500cc Indian. I know it was almost as fast as a 500cc Matchless single - how do I know that ? We had plenty of policemen around even in the old days. And it went from there. One thing about motorcycling - you have to have a sense of humour, and no sense of pain.
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Not one bit of relevance to the subject of this thread.
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If I had a bit of spare cash, what I would really like to do would be to build a G45 Matchless, using 1963 Matchless 650CSR bits, especially the cam follower setup,and also a staggered roller crank. Then smuggle it into those races that cater for 500cc manxs and G50s. I don't believe the G45 ever reached anywhere near its full potential.
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Any Knoodle prepareing a Short stroke for Raceing , is going to go through it .
Port Match , Check faces , dedagg & deburr , ascertain alignment & Fit .
Amougst other dark & mysterious processes .
Which should be good for 4 Hp. or better .
The more painstakeing & polished , the more like 10 or more HP .
Were the ' production ' short stroke rods used in the 74 works Space Frame devises ? :?
Port Match , Check faces , dedagg & deburr , ascertain alignment & Fit .
Amougst other dark & mysterious processes .
Which should be good for 4 Hp. or better .
The more painstakeing & polished , the more like 10 or more HP .
Were the ' production ' short stroke rods used in the 74 works Space Frame devises ? :?
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