Yamaha crankshaft , 650 vs 701 why stamped different?

[RoscoeJ]

I know you can use ,a 650 crank in 701 ,or vise verse ,question is : why is the crank from a 701 stamped 6M6, and a 650 crank stamped 6R7 ,even hotrod cranks shows same number for 1990 650 , but there 701 only goes from 1998.. What are ,or were ,the differance in the older cranks? 6M6 vs 6R7 ....
I did search form first ...

 

[kevbo]

6m6 have slightly thicker webs than 6r7. the 650 coupler shaft was bored to save weight. 760 cranks have rods that are not machined and have sheetmetal wear ring to save cost.



S

 

[Midlake Crisis]

I have a really clean, tight 650 crank I was getting ready to use in a ported 62T/61x 701 - good idea or no?

 

[kevbo]

They are great for 701s.