Does anyone know what the compression ratio is for a Honda hobbit PA 50? RPMs would be good information as well. I would like to know These numbers on a bone stock bike. Unfortunately, the manual does not allude to these numbers.
Compression Ratio/RPMs
Re: Compression Ratio/RPMs
The compression ratio is listed as 6.5:1 for the 25-30 MPH version. (113.78 to 170.68 PSI, tested by kicking the engine over with the throttle fully open).
Re: Compression Ratio/RPMs
max rpm? stock is like 6000-6500 on a pa50-2, probably 4500-5000 on a PA-1.
Re: Compression Ratio/RPMs
Thanks guys!
Re: Compression Ratio/RPMs
so compression directly relates to RPM? interesting, well yeah, that does make sense. i have to read more.
Re: Compression Ratio/RPMs
Compression ratio is just the difference in volume between Top Dead Center and Bottom dead Center.
Or, in 2 stroke applications like Mopeds, the difference in Trapped Volume between when the exhaust port closes and top dead center.
A low compression ratio Can prevent you from attaining top RPMs, because you run out of Torque before you hit any other limiting factor.
A very high compression ratio can prevent you from reaching high RPMs because the act of compressing all that gas on the upstroke is a static tax on power. You get more Torque out of the power stroke, sure, but at a certain point in the rev range it'll start costing you power.
Way better to use a tuned pipe to boost your compression ratio when you're near peak power anyways, that way you get an engine that revs freely but still delivers torque where it's needed.
Re: Compression Ratio/RPMs
According to Honda Belgium 5950rpm max for PA50-1 and 6460rpm max for PA50-2 both giving up 2hp at 5500 and both with 6,7:1 compression ratio.
Graham Motzing Wrote:
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> max rpm? stock is like 6000-6500 on a pa50-2,
> probably 4500-5000 on a PA-1.
Re: Compression Ratio/RPMs
> Rebel Moby wrote:
> -------------------------------------------------------
> According to Honda Belgium 5950rpm max for PA50-1 and 6460rpm max for
> PA50-2 both giving up 2hp at 5500 and both with 6,7:1 compression ratio.
>
> Graham Motzing Wrote:
>
> -------------------------------------------------------
> What would the estimate be on a 70cc kitted Hobbit? Is there a way I could calculate this? Yes I know this is an older post but thought I would still ask.
> > max rpm? stock is like 6000-6500 on a pa50-2,
>
> > probably 4500-5000 on a PA-1.
Re: Compression Ratio/RPMs
That totally depends on your setup. Somewhere in the 9k-11k range isn't too hard by slapping together parts.
Re: Compression Ratio/RPMs
I like to take .8mm off the top of cylinder on stock Hobbit.
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