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Stroker opinions please

Ok Guys; I just did a 68 mile run at 78mph on the way to the VA and back. Topped it up when I left and topped it up when I got back. 39 mpg running at 78-80, does that sound about right to you with the mods we talked about above? The bike seems to run effortlessly now and a roll on anywhere steps right out smoothly and it seems to run a bit quieter too, sorta like it's not working nearly as hard as before.
 
Ok Guys; I just did a 68 mile run at 78mph on the way to the VA and back. Topped it up when I left and topped it up when I got back. 39 mpg running at 78-80, does that sound about right to you with the mods we talked about above? The bike seems to run effortlessly now and a roll on anywhere steps right out smoothly and it seems to run a bit quieter too, sorta like it's not working nearly as hard as before.

That is the good news. What's the Bad news part?
 
Great point and that is what I was thinking. So based on that statement, would you agree that:

Since the faster bike weighs 25% more, he would need 25% more torque to offset the weight he is pulling. And if so, then can the extra 25% of required torque be developed purely by 7 cu/in of more stroke.?

I admit I am no engine builder nor have I ever raced another bike but that does seem like an awful lot to me. Does it to you?

Your right about a "lot of little pieces" all adding up to 1 big difference.
I have this feeling the heavier bike is hiding a Nox bottle.:p
We really don't have enough data. But you would need 25% more torque at the rear wheel. He has an 8% increase in displacement, and depending on the heads, VE could actually increase and give 10% maybe 11% more torque. ANd that torque would be at a lower RPM. If he is geared lower, he could be multiplying the torque, for even greater torque difference. Even things like weight of wheels come into play. Lighter wheel allow for acceleration greater than the weight reduction (flywheel effect). Also, the stroked motor would have a flatter power curve, thus if the rolloff began at an RPM lower than than the peak torque of the shorter stroke motor, game over.
I think they need to weigh the bikes and remove some guessing.
 
That is the good news. What's the Bad news part?

The bad news is that I used to get 42mpg at that speed. I'm not complaining at the 39mpg as now I feel that i'll at least run even up or even beat him the next time we race. I was apparently running too lean to get the best performance from my engine. I don't have access to a dyno around here so the next time I get to a rally perhaps I'll have it done to see if I can pull a bit more performance from the bike but, for now, I think my bike is good to go. Wow, this turned into quite a discussion, what with weight % vs hp vs torque and all and the volumetric efficiency. Gets one to thinking just how much goes into a build other than just the actual work.
 
Wow, this turned into quite a discussion, what with weight % vs hp vs torque and all and the volumetric efficiency. Gets one to thinking just how much goes into a build other than just the actual work.

It can get a lot deeper. Most understand VE (volumetric efficiency), but very few mechanics even know how to maximize combustion effeciency and thermal efficiency, and both help with HP and torque. Then you can get into rod angles & rod/stroke ratio, piston speeds, velocity and pulse tuning, and their relationship into the head (especially when both valves are open) temp, pressure, and humidity compensation, matching gearing with motor characteristics, etc,etc.

:bigsmiley20:
 
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