Topic: Final drive: getting an extra bit of power from CB750K

[HondaMan]

One of the "secrets" to getting a little more power on the ground in the Production Racing class (stock) is to reduce bearing widths. In the case of the CB750K0-K5, the final drive bearing was usually a 2-row #5206 bearing. Nice and rigid, but causes drag at speeds above 50 MPH. I once saw a K0 with this narrower bearing and the slightly longer wide shoulder on the drive shaft. I got one for my K2, and it helped! And, it lasted over 100,000 miles, so it doesn't seem to be a wear issue...

You can make this arrangement by installing a tubular collar on the drive shaft that is the difference in length between the #5206 double-row and this #6305 single-row bearing. This bearing is the same size as the one used inside the rear wheel's sprocket hub, but with the oil seals popped out.

Although I never dynoed it for a difference by itself, the math shows that about .5HP extra will be available at full load in 4th or 5th gears.

[chung]

That looks like a K7-8 beside a K0-6?

[HondaMan]

Actually, the one in the cases is the K0-1-2 "sometimes I saw it" genuine Honda parts. Mine happens to have it now: you used to be able to find the 2 different types in the Honda parts books long ago. That's how I got it. After K4, I think all of them had the 2-row bearings, but Yoshimura offered the single-row bearing and shaft with the CR750 "kits" of the 1970s era.