72cc preformance questions and Where to buy preformance parts?

[matty_77]

Hey guys,
I recently purchased a chinese crf50 electric start
I changed the motor to a kickstart 72cc I think. It says 48cm3 on the bore. Yet it has larger inlet and exhaust inlets than the 50 that came out of it so i am asuming it is really a 72cc as It has way more power.

I am just wondering where you can buy things like stiffer valves springs, Cam and Bigbore kit for them?

Can you just put a 90cc head and bore off another chinese motor or do you need to change the crank or put a differant piston.

If it helps I can post a picture of the motor tonight

 

[sean01]

if you measure the installed height and diameter of your current valve springs and email akunar im sure he will have something compatible..
or just add more shims on your springs to bring up the spring rate.. but not too much without checking for coil bind..

as for the 90cc top end you'd have to check everything.. chinese engines can be weird..

 

[The_GDFP]

Chinese "90" is 86cc, and the same bore and head as you have, just a 49.5mm stroke instead of the 41.4 it has. TB 88/95 kits will bolt on. Swapping the cam and springs should not be needed. Porting is. Thinner head gasket, after measurements, usually boosts torque if you don't swap to a bigger bore.