cb72 crank in cb77

spanky · Post by **spanky** » Sun Apr 02, 2017 10:44 pm

Can anyone tell me if i am able to run a cb72 crankshaft in a cb77,the only difference i can see is the splines are different on the drive end?

G-Man · Post by **G-Man** » Mon Apr 03, 2017 5:17 am

There are different sized balance holes to match with the piston weights on the two cranks. The CB77 has larger holes (around 23mm from memory) compared with the CB72 (around 20mm).

The spline changes is an early / late issue and was common to both cranks. Shallow is later.

You will probably see more vibration from using the 'wrong' crank but I have seen cranks built out of odd parts just to be able to get a working crank 50-years on.

G

DJM · Post by **DJM** » Mon Apr 03, 2017 5:55 pm

I've done this in the past with no real problems, as G-man says you might get slightly more vibration, or perhaps the same vibration level at different engine speeds but it shouldn't be a big issue. Don't try and run a CL crank in a CB engine as it's missing an oil hole for the starter sprocket. You can run a CB crank in a CL OK if you block off the hole.