Hi,
I guess I could have phrased the term torque better. We had "more torque" with the cylinders firing on the same stroke than when the cylinders fired on alternate strokes. Sorry bout that, CliffC
Type II "Twingle"?Brewsky,
Its been so long ago I really don't remember. The Type II's did vibrate more than the Type I's anyway and the Type I would rev higher. The first bike I ever rode or owned was a 56 honda 250 single that I bought 3 months after I got to Japan ($65.00). It was set up for scramble racing, running on alcohol with a modified head and a 1 3/8 inch Amal carb. The biggest problem was too much rake on the front which caused the front forks to bend when coming off certain jumps. After I think three fork changes I got rid of the bike. It was one heck of a hill climber. CliffC
Cliff: I can't understand why changing from alternating to simultaneously firing of the cylinders would cause any increase in torque. It shouldn't matter weather the piston's are pushing on the crank at the same time or not, the overall torque output of the engine would be the same, everything else being equal; as in this case the stroke is not changing. When you go from a 250cc twin to a 250cc single "traditionally" the stroke would be longer in the single. I say "traditionally" because the newer 4 stroke's have been using over-square designs like the XL250 of '72-73 which uses a bore and stroke of 74mm x 57.8: http://motorbikearchives.com/Bike-Tests ... World.html There have been many debate's on-line and even back before the internet about torque vs stoke vs bore vs big valves vs high-rpm vs multiply valves (hondas 32 valve v4 comes to mind) add more variables ect. ------but what I learned in auto mechanics 101 in high school: for torque you need long stroke, large flywheels, small bore got completely erased when I started reading Cycle magazine in the early '70's and found kevin Cameron's TDC column on technical subjects. I have been reading his column every since and when cycle mag died in '94 (or there about's) he has been in Cycle World. I tried a search for articles by him as I know he had wrote about it; I found the TDC columns in a book at amazon: http://www.amazon.com/Top-Dead-Center-C ... dogpile-20 Cycle world has a tech line forum and they had the same topic: http://forums.cycleworld.com/archive/in ... 34543.html It's hard to read but they make the point that with large bores, big valves, water-cooling, modern fuel and spark delivery a single can have the torque down low and still rev high enough to make significant h.p. Brewsky, as for comparing the Honda 250cc twin with the suzuki 250 single, the Honda is the same as the 250's made in the early 80's, they haven't up graded the basic mechanicals since: http://www.chrisharrison.net/CM250/ and I don't know what model the Suzuki is but I would guess it is a modern design. But discussing the difference of twins and singles is not the point; you are just going from a twin that fires alt. vs sim.; wouldn't this throw the balance of the engine off? is it more felt than can be showed on a dyno? Was there a history to doing this as it seems a lot of work; wouldn't it be better to put the money in a bore job and possibly get more torque out of the engine? Jensen; why do you think there would be more feeling of torque, I would like to hear a technical explanation: I just can't get my mind around it. It's amazing, after 40+ years, I am still learning new things about these bikes. Clarence Hi Clarence,
You have to remember in this case you are turning the engine at lower RPM and you have two cylinders totaling 247cc on the power stroke versus one cylinder totaling 123.5cc on a power stroke. Thats about the only way I can explain it. Like I said before it was good on the short straightaway tracks with hilly terrain. The Honda's of the 60's couldn't compete with the later bikes due to weight and power(talking 40 plus years). Sort of like an Offy at Indianapolis trying to compete against the current Honda V8. CliffC Brewsky
I can understand why someone might do this for a different sound and feel, however you cannot make an engine deliver more torque simply by re-phasing the crank. You get more peak torque at the instant when two pistons are pushing simultaneously. Don't forget though that you have another stroke where nothing is happening at all. Therefore the average torque available for acceleration will be pretty much the same, The reason to do it for scrambles and road racing is that an engine that produces it's torque in lumps with large gaps in between is easier for humans to control. If a 'big bang' engine starts to spin up the rear tire it has 720 degrees of (crank) revolution before it puts the next dollop of thrust down, therefore providing an opportunity for the tire to grip again. It's like anti-lock brakes in reverse. Cheers G '60 C77 '60 C72 '62 C72 Dream '63 CL72
'61 CB72 '64 CB77 '65 CB160 '66 Matchless 350 '67 CL77 '67 S90 '77 CB400F Clarenceada,
The best way I know to explain the difference is to look at the definitions of both. Power = Force x Distance / Time Torque = Force x Lever Arm Length Power is the ability to do Work (Force x Distance) in a specific amount of Time Torque is an instaneous amount of Force applied at a specific Lever Arm Distance, and is independent of Time All other factors being equal, (bore/stroke, cam timing, compression ratios, ignition timing etc,), switching the same engine to fire 2 cylinders at the same time should double the torque since you would have twice the instaneous force applied at the instant they fire. That is not to say the bike would be any faster over a given distance, such as a 1/4 mile, but it would have a larger "kick in the pants" feel at lower rpm's, like a cruiser. 66 dream, 78 cb750k, 02fz1, 09 wing
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