Thread: Big Guy
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Old 08-19-2014, 01:35 AM
ajoh ajoh is offline
Motorized Bicycle Elite Member
Join Date: Mar 2014
Location: australia
Posts: 161
Default Re: Big Guy

i agree with you barely the example i was pointing at, at being a little extreme for this topic here was car motors specifically racing engines

but for these types of motors yes you are right 2strokes make more hp for the same cc........

i been looking for 99cc hf motor but it seems HF don't list them only 79cc
ahh well i'll look else where

Originally Posted by BarelyAWake View Post
If you're comparing two of the exact same design types, differing only by displacement - then in this very specific instance displacement might help dictate which one is more powerful, but it's quite unlikely to be double the HP for twice the size even then.

The 50cc I believe qualifies as a small motor, the above two stroke examples could be the commonplace motorized bicycle two stroke kit motors (2hp) vs the 50cc Morini, KTM50 & their clones (9hp), of which are 4x the HP at a minimum vs their exact same displacement comparison.

A common small displacement four stroke example relevant to this application would be the 99cc Harbor Freight Predator vs the 49cc Honda CRF50 & clones, both of which are just about 3hp... despite doubling the displacement.

Displacement alone means very little in generality, pretty much limited to knowing which parts ya need to order, there's so many flavors even with common engine types - piston ported, case inducted, reeded or the flathead & OHV conundrum, the bore vs stroke ratio, compression ratio, the quality of manufacture... there's too many variables, just to many exceptions to list lol, let alone to trust a catchphrase for landscaping equipment, give weedwackers & model airplane engines a google - similar in displacement, it's amazing what 14,000rpm+ can do
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