Hi Guys,
I am a little bit puzzeled by the compression ratio of my standard 31ci single. I have read in a few places that it should be about 8.5 to 1. I have the head of another motor and used a syringe and perspex with a hole in it to fill the chamber and got 49cc (sorry i work in metric)
The specs for the engine online teel me its a 90.5 mm bore and a stroke of 77.7 mm.
Therefore Volume of cylinder equals V and using my equation i end up with 499.560cc.
So Compression ration is swept volume plus head CC divided by the head volume or 499 + 49 + 548. / 49 =11.18.
So my comression ratio is 11.18 to 1. I know there is a bit to add for headgasket so it may drop a bit but not enough to go to 8.5 to 1.
I havent had the engine apart so i dont know if the piston comes flush with head or below. That would also make a differrence.
I may have missed somthing so maybe you could set me straight.
Cheers
Baz
