RPM limit on stock cdi?

Rigz

Member
Mar 1, 2018
50
5
8
39
orlando
Wondering about how much rpm the stock cdi can handle. Iv read that the stock cdi can only handle about 9k rpm. Iv only been able to reach 8800 rpm with my lightly modified 66cc China girl 38mm stroke type A piston. I completely gutted the stock pipe. I have a short port matched intake and rt carb. I cut and smoothed the slag out of the transfers and polished/smoothed out the intake/exhuast ports. With a 38 tooth gear and 26 inch wheels I'm at about 42mph. I have a tach and speedo.i can can feel the pipe in resonance at about 7000rpm so I thought I passed the power band at 8800 and that's why it wouldn't rev higher. But after reading about the cdi I wonder if that was the limitation
 

xseler

Well-Known Member
Apr 14, 2013
2,883
126
63
OKC, OK
Just my opinion, but I'd be scared to rev it much higher than that if I planned on a motor powered ride home........

Good luck in your search for answers!
 

Rigz

Member
Mar 1, 2018
50
5
8
39
orlando
I know that these motors don't like to handle sustained rpm over 5k rpm without balanced crankshaft and some lightening of the piston and or a better needle bearing/bronze bushing. I am testing the effect of mods designed for high rpm and wondering if the stock cdi will limit that. There's guys that are going in the 70s saying that the stock cdi is fine. Although I gave no idea what there gear setup is like
 

Larry Trotter

Active Member
Nov 26, 2017
157
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Likely the CDI will be good for more rpm than the engine is. Probably you are needing more spark advance to go much higher than 8K. Larry