I'm looking for a crankshaft for a ciao and a guy has one that has been cut for better performance. I'm not too familiar with this. I know it's has to do with the timing but that's it. Can anyone explain it further? Am I going to have to do a buttload of other adjustments like on my points or anything? I'd rather just get a stock one if it's a hassle. Any help is appreciated.
Cut crankshaft
Re: Cut crankshaft
a ciao has a rotary valve intake, which means the intake hole lines up over the crankshaft web. The web (web= half a crankshaft) has a notch cut into it which allows fuel/air to flow into the motor. A "cut" crank has a bigger notch, giving more time for the fuel/air to enter the motor, and thusly more power, faster, etc... if done properly, rotary valve mods can create fantatstic power. ... but I don't want to start that thread over again.
Re: Cut crankshaft
cut crank. ten mill on the right, five in the right. it changes intake timing not ignition timing. plus you can't adjust vespa timing.
Re: Cut crankshaft
You can adjust Vespa ignition timing, just not a lot. It's all in the point gap.
Re: cut cranks, though, you might find the attached picture informative.
Re: Cut crankshaft
You're right James. i was just simplifying.
Dave, James knows his shit and shares is knowledge on most Vespa threads. Take heed.
Re: Cut crankshaft
oh, thats cool. i actually thought that there was a small notch going down the crankshaft balancer weight thing. does a stock shaft/rod look anything remotely similar to that or is it way less radical in design?
Re: Cut crankshaft
James' pic is a stock crank mine is a pic of a stock cut crank and it should have read 5 mil on the left, 10 on the right meaning that's how far back I cut the "ramps" from their stock position. if you look at James' pic again you'll see they form a pie wedge shape, where as when cut, they are almost straight across. hope that makes sense.
Re: Cut crankshaft
oh, ok
Re: Cut crankshaft
So James would you suggest it in the end if I'm not super excited about splitting my case again and again if it doesn't work out? i've got a feeler gauge to adjust my points and dropping my engine out isn't that big of a deal anymore. but I'm at the point where i'm done modifying this bike, i'm happy with it's performance, and just want to ride it for pete's sake.
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