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Old 06-17-2009, 09:39 PM
matt167 matt167 is offline
Motorized Bicycle Elite Member
Join Date: May 2009
Location: usa
Posts: 420
Default Re: Will an 80cc motor handle my weight?

Originally Posted by lowrider View Post
What about the space in the head? I really dont know anything about it but its my understanding that there is space there not taken into account in the equation.
yes, but adding those numbers into the engine size figure is incorrect... the formula is BORE X BORE X STROKE X .7853982 .. adding the extra cc from the cylinder head is incorrect as the head space in the engine is the combustion chamber and has nothing to do with the engine size.. they do that on the china engines specifically to make them sound bigger than they are...
could even take it a little farther.... if you had an engine that the pistions were in the hole say .025 instead of being at 0 deck, that would equate to about 3cc ( bore size effects this ) that would also become part of the combustion chamber, and then if you were to add a .045 compressed head gasket, that would add another 7cc to the combustion chamber.. so if it was say a 100cc engine, by figuring it the way the china's are advertised figured, it would be 110cc, because of a thick head gasket and a pistion that doesn't come to 0 deck.... but it doesn't work that way
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