HP is falling off on both the 250 and 351 after 8K rpm or so. Is the 351 making good power off the limiter? Probably not. Does the 250 make more power at 10500 rpm than the 351? Perhaps. But peak power at 10,000 rpm is not what I was looking for in the 351. I'm happy with it.

 

[QUOTE=durielk;482835]RPM 9500
stock 18hp 10torque
mod'd 26hp 15torque

The mod'd bike will get there faster, speed or distance, take your pick.
QUOTE]

The mod'd bike will get there QUICKER.

Given the same rpm, power is a non issue as long as the rpm can be met, the speeds will be the same. Mod'd or not.

500hp turning at 9,500 rpm is just as fast as 1,000hp turning at 9,500 rpm.

The original issue was can the 351 go faster ( achieve a higher top speed) than the 250, AT the same rpm with the same gearing. the answer is no if both bikes can achieve the rpm.

 

These are not my dyno sheets, these are from member ZRexRich and are from his 351 dyno runs.

Looking at these two charts, i fail to see what you are talking about. The 351 is making power all the way to reline, and almost 10hp more than stock with the cylinder and exhaust at the same rpm and you claim it wouldn't be as fast ?





???????

 

agreed,,,, as am I. I prefer the torque and low end over a screaming banshee.
The 351 is the perfect bike all around. I am running a 15 tooth front sprocket and can still paddle through anything with the clutch fully disengaged and almost idling. That is usable torque. my bike rarely sees 8k let alone bounce off the rev limiter. there is no need for that ever on this bike.

 

think of this:
this should simplify things and if it doesn't ,,,
I can't.
2 electric motors, motor A is 19 hp. motor B is 34hp.
Both motors when plugged in will turn 1750 rpms.
put a wheel on each motor. which wheel is turning FASTER???????
neither,,,, because both motors are turning at the same rate of 1750 rpms

 

Which engine/wheel combination will overcome air resistance easier and achieve the higher top speed ?

???

 

+1 on the lesson...your correct!

The only reason my 331 has a higher top speed is it has the extra HP to pull 10000rpm is 6th gear. The 250 had a real problem getting over 8500rpm in 6th gear.

With the same stock 250 gearing on the big bore bike, it has a lot better acceleration & torque. Lots of fun usable power.

I might try a 15T sprocket in the future, just to have a play... But don't want to loose the great around town power!!

 

Im sorry, but if your gettin down to being this specific you dont really know motors..... bigger cc= more power. you are adding 100cc to only a 250cc motor.

That would be like taking my GMC Sierra with a 5.3L (324CI) V8 and upgrading it to a 7.4L (454CI) V8.... Come on... its alot more power.

 

I agree that if the motors are turning the same rpm, etc.; then they are going the same speed. But....

No way your going to bounce a 250 off the rev limiter on flat ground. Therefore any increase in displacement, mod's, or HP in general is going to get you a faster bike.

Generally when guys talk about faster bikes, they are indicating faster acceloration. Your "faster" is only discuss at one place.... the salt flats in utah.

 

If your bouncing off the rev limiter you are doing something wrong....

Its soooo annoying when sport bikes do it.....