Milwaukee-8 camshaft testing & dyno 114"
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,862
Likes: 7,981
From: poway
I've never understood the comments on this Forum that conclude V Twins can run up to 6k rpm we should run them high rpm.
if that's the case, why not just buy a Japanese 6 cylinder bike with a half inch stroke and run at 10,000 rpm all day? I don't get it. At all. Harley's are stroker motors for high torque at low rpm. Because a different mode of operation is possible, why would you restrict operating there?
I rode the 4 cylinder Hondas. They start picking up torque around 5,000 rpm, like a 2 stroke snowmobile. Exactly what I do not want in a motorcycle.
if that's the case, why not just buy a Japanese 6 cylinder bike with a half inch stroke and run at 10,000 rpm all day? I don't get it. At all. Harley's are stroker motors for high torque at low rpm. Because a different mode of operation is possible, why would you restrict operating there?
I rode the 4 cylinder Hondas. They start picking up torque around 5,000 rpm, like a 2 stroke snowmobile. Exactly what I do not want in a motorcycle.
Road Warrior
Joined: Nov 2022
Posts: 1,532
Likes: 536
From: MN
Disagree. Strokers have a longer moment arm crankpin yielding higher torque for given displacement. There would be various bores and strokes for given displacements otherwise.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,862
Likes: 7,981
From: poway
Do the math.. The longer stroke means less square inches on the top of the piston if the displacement is the same.. Less square inches means less force on the rod which ends up to be the same torque.. Rod to stroke ratio in important here.. If the same they generate the same amount of torque.
Road Warrior
Joined: May 2017
Posts: 1,797
Likes: 2,292
From: WI
I've never understood the comments on this Forum that conclude V Twins can run up to 6k rpm we should run them high rpm.
if that's the case, why not just buy a Japanese 6 cylinder bike with a half inch stroke and run at 10,000 rpm all day? I don't get it. At all. Harley's are stroker motors for high torque at low rpm. Because a different mode of operation is possible, why would you restrict operating there?
I rode the 4 cylinder Hondas. They start picking up torque around 5,000 rpm, like a 2 stroke snowmobile. Exactly what I do not want in a motorcycle.
if that's the case, why not just buy a Japanese 6 cylinder bike with a half inch stroke and run at 10,000 rpm all day? I don't get it. At all. Harley's are stroker motors for high torque at low rpm. Because a different mode of operation is possible, why would you restrict operating there?
I rode the 4 cylinder Hondas. They start picking up torque around 5,000 rpm, like a 2 stroke snowmobile. Exactly what I do not want in a motorcycle.
Now, why am I doing that instead of getting a cam that emphasizes low end torque? Because I want to, and I can. If I blow the motor, oh well, I'll build another or pay someone to do it for me.
I don't have the time/space for another Ducati right now, so this is helping fill that hole in my heart until I can get another one.
Road Warrior
Joined: Nov 2022
Posts: 1,532
Likes: 536
From: MN
Do the math.. The longer stroke means less square inches on the top of the piston if the displacement is the same.. Less square inches means less force on the rod which ends up to be the same torque.. Rod to stroke ratio in important here.. If the same they generate the same amount of torque.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,862
Likes: 7,981
From: poway
Now for the same bore, if you increase stroke, you increase displacement and therefore increase torque.
Add:
Actually there will be calculus involved if you want to integrate over the stroke.. In that case I cheat and use a spreadsheet.. Analysis at a rod angle of 90 degrees is good enough tho.
Last edited by Max Headflow; Apr 25, 2023 at 05:56 PM.
HDF Community Team
Joined: Oct 2018
Posts: 4,345
Likes: 3,392
From: Seattle
While yalls are exploring the merits of rod length...
I'm just over here debating between the 22XE and the 777XE.
Potentially 125hp at 6000 RPM. Redline of 6200...
Versys 22XE at 120hp from 5500 to 6000, redline it at 6200 and it'll carry that 120 all the way. But the 22XE has so much low end torque as well.
777XE would require me to get 5.5injectors though, and it's a more expensive cam, would be 500$ for me.
Where as a 22XE is 352$
I hear though it's bad for longevity going over 5500~6K RPM.
I'm just over here debating between the 22XE and the 777XE.
Potentially 125hp at 6000 RPM. Redline of 6200...
Versys 22XE at 120hp from 5500 to 6000, redline it at 6200 and it'll carry that 120 all the way. But the 22XE has so much low end torque as well.
777XE would require me to get 5.5injectors though, and it's a more expensive cam, would be 500$ for me.
Where as a 22XE is 352$
I hear though it's bad for longevity going over 5500~6K RPM.
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Road Warrior
Joined: May 2007
Posts: 1,433
Likes: 383
From: Arkansastan
I was one that thought longer stroke made more torque, shorter stroke made more HP, hence the longer stroke allows more "burn per stroke" (piston has to travel further, allowing gas to expand more) and why long stroke, low RPM engines are used in diesels. ??
Road Master
Joined: Mar 2013
Posts: 817
Likes: 380
From: Central Ohio
They will make similar tq / hp (it's improbable they would be exact, as even mirror image builds can be different). What changes is the rpm where each one peaks. Diesels are a different animal, they do generally have longer strokes but there are over square engines around