Convertion

You can't.

There is no direct correlation, it depends on the efficiecy.

A 50cc engine may produce more HP than a 150cc one, although it would probably wear out quicker!

I agree with Del. You're gonna need to know the efficiency of combustion to get a mathematical correlation between the engine volume (cc) and its output power (HP)

http://www.simetric.co.uk/si_cc2hp.htm gives full details.

Thank you very much.

Del the Cat & espresso should too refer the site.

Thank you for wasting my time... My original assertion is correct....

The site offers a guide and is very informative (if you didn't know it to start with)...

A guide is NOT a conversion.

Grumpy Del

Yeh my Yamaha FS1E was never as quick once I put an ATCO lawnmower engine in it even though they were both 50cc !

They are right to say there is no conversion. If you have a specific engine in mind, maybe that's a different story. You say a 125cc motorcycle engine. The SIMetric site says about 33hp. However, if you go to the Honda website and look at a few of their 125cc models, the output ranges from 9bhp to 15bhp. So if you're happy with a possible error of about 360% in your calculations, that's fine.

Thank you very much pwslack your gesture site is very usefull majeed

Well thats a bit of a duff link...

that just shows Del and Expresso are perfectly correct in saying there is no direct link between cc and horsepower...

The list gives a conversion factor of between 1 and 234 cc to the horsepower...

What utter nonsense - John.

If your engine was manufactured in russia like the moped called RIGA that is powered by a 50ccm engine with the output power of 2.5hp/100km at 2.6+liter.

Yet, if it was a former east-german made SIMSON powered by a 50ccm engine with the output power of 3.6hp/100km at 1.8+liter then you can see the difference in efficiency.

(Not to mention the russian built bike would wear out after about 10,000km while the other would last 3x plus longer.)

I think the others were right. There is no direct comparison between ccm to hp due to efficiency factor!

Put it on an engine Dynamometer

There was an old method used for taxation & I believe insurance, many years ago in the UK, where 1 liter engine capacity was considered to be 10 HP if I remember correctly..

I was very confusing to a lot of folks and has not I believe, been used for years!!!

Which was I believe the reason that HP & BHP were both used, I could be wrong there though!! Maybe someone else can give us some solid facts in this area....