| He's right mountain ....... although 4 strokes only have a power stroke every 2 crank turns (720 degrees) , the ignition fires every 360 degrees because the flywheel is turning one to one with the crank ........
In other words every second rev there is a wasted spark in a single cylinder 4 stroke engine that uses a crank triggered pickup ......
The only way around it would be to time the spark off the end of the cam which runs at HALF crank revs like early Honda SL/XL and Honda posty bike engines do .... or in the case of a 4 cylinder bike .... run a camshaft driven distributor like a car does .......
Incidentally , since 4 strokes only fire every 4th stroke ie 2nd crank rev ..... they SOUND like they aren't revving as high as they really are (they'll sound like they're doing half their actual revs) ..... So you CAN'T accurately judge how high an engine is revving by the sound of it's exhaust note ..... Only the crank which makes no "Bang, bang" noise revs ...... the piston which is driven by the "Bang , bang" noise reciprocates (goes up and down like a yo-yo ... LOL) ..... so you'd need either a mechanical crank driven tacho or an electronic tacho that measures pulses every 360 degrees ....
Last edited by Cactus Jack : 25-07-2008 at 05:09 PM.
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