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Old 01-22-2015, 11:24 AM
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mapbike mapbike is offline
Motorized Bicycle Elite Member
Join Date: Mar 2010
Location: Central Texas
Posts: 5,379
Default Re: Top Speed, 80cc Chinese motor? what is the record?

Originally Posted by Davezilla View Post
I definitely agree on the difference between a full throttle run and the pure torture of the race tracks where rpm needs to stay up by any means possible so heat goes up the same but with less opportunity to cool the engine...

Wow Map if yours is running 8950 to hit 52mph your engine probably spins as fast as mine if they were both geared the same... Compression is important on a 2 stroke for low rpm torque and power, but as the rpm's climb up it becomes less important so the power's probably about the same as mine at those rpm's too...
I know my static compression ratio is 12.7:1 but the actual is quite lower since the actual is measured from the top of the exhaust port instead of the bottom of the stroke like a 4 stroke engine, this ratio varies tho on the 2 strokers because as rpm increases and if an expansion chamber is used the ratio can go up a few numbers so it's more like a virtual compression ratio that falls somewhere between static and actual.
All I know is that that engine sounded like it was gonna take flight or blow like a stick of TNT at top speed....LOL..!

I may have just got lucky with port timing and such on it since I did nothing scientific really, just a few measurements and guess work with some calipers, some filing and some dremel work, I had planned to take the deck height down some, but then just decided to see how it would run without changing it.
I dont always ride WOT, but when I do..I do my best to keep the rubber side down..Ride safely my friends!
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