Topic: CB750K8 rod length

[maxheadflow]

Anyone know what the center to center rod length is for a 78 CB750K? If it changed over the years it would be interesting to know.

TIA
Max

[Jerry Rxman Griffin aka MuthaF'er]

All the same

[maxheadflow]

Good to know, thanks..  Anyone got a rod around that the are willing to measure.  Lower Id to Pin ID and diameter of the lower hole with a caliper is fine. 

[kmb69]

Stock SOHC 750 rods are 116mm, 4.567" center to center.
Big end is 39mm, 1.535".

[maxheadflow]

Thanks  bunch.

[scottly]

Why are you asking? Are you looking for an easy way to raise compression??

[maxheadflow]

Why are you asking? Are you looking for an easy way to raise compression??

Rod length is needed to calculate corrected compression ratio.  You can also compute rod to stroke ratio.

[PeWe]

CB900 DOHC has 1.5mm longer rods, fits the CB750 crank. These rods are slightly thicker than stock CB750. I have a set on the shelf.
There are threads about it.
Problem with too high piston crown, thicker base gasket needed, making issue with cam chain that suddenly is short. Might work with turbo pistons if getting a set cheap and avoid thick base gasket and cam chain issue. Lifting cylinder with base gasket can be compensated by grinding down the cam holders a little.

I wonder how the valve train geometry will change if the package on head is 1mm lower?

[maxheadflow]

Not sure why you would go to longer rods.  I larger rod to stroke ratio is nice but the R/S ratio is already 1.84. If you are thinking a little more TQ due to the longer rod, I'd expect it to be minimal.

Cutting the cam tower down 1mm will move the contact point outward at mid lift. I'm really not the well experienced on CB750 heads other than guides and valves years ago.