Low Compression v/s High Compression

[Sidehacker]

Will a high compression u motor get relatively the same top speed crusing as a low compression head.

[JoJo357]

*Keith, hope this answers your question.

*Model U Flathead 74c.i. 1209cc-- 5.0:1 Compression Ratio.
32.5 hp @ 4200 rpm. 135 km/h = 84mph ?

*Model UL Flathead 74c.i. 1209cc -- 5.2:1 Compression Ratio.
37.5 hp @ 4200 rpm. 135 km/h = 84mph ?


*M.A.D.*

[chuckthebeatertruck]

Yes.

the compression is laughably low.

[Sidehacker]

That totally answers that question now since a 3 speed and a four speed have 1to 1 on top gears do they also have same top speed.

[chuckthebeatertruck]

No.

The theory says they can cover the same distance at the same rpm in top.

In reality, the higher horsepower bike will pull more gear.

What does that mean?

Torque gets you moving -- horsepower gets you going.

A lower compression, lower horsepower bike will not pull as many rpm in top as a higher compression, higher horsepower bike (if all else is identical).

They will have the same theoretical speed -- but it won't ever quite work out that way.