Topic: CB750K & F Conrods

[mick7504]

What is the best way to ID between the two?

The rod on the right is from an F motor with the thrust side squared off at the base and the rod on the right is from a K motor with a full circular thrust side.

Is there another way to ID between the two?

Mick

[Jerry Rxman Griffin aka MuthaF'er]

Mick,

I don't think there was ever more than one part number for the rods other than by weight. ie just changes along the way like what you see. ie one rod fits all engines. Bolt differences yes. Just so happens I have my 75/76 F parts manual out and the rods are all listed as -300 rods. My one original rod from my 75 that is permanently affixed to the piston with the big hole (thats how I know it's the original  ) in it has the rounded base.

How's the weight on each? What are the weight codes on the side of the big ends? D, F, H ?

[mick7504]

Thanks Jerry

I've weighed the rods and shown on the picture the weights and the codes for each.

The cap bolts both weigh in at close enough to 15 grams each even though 1 is approx 2mm longer and has slightly more shank length under the head.

It also protrudes through the flange nut approx 2mm whereas the shorter bolt protrudes only slightly through the undercut nut.

Mick

[Jerry Rxman Griffin aka MuthaF'er]

Different bolts, huh? Which F model? Perhaps the 77/78 F since it used different/better/stronger bolts?

[mick7504]

Jerry these rods are from a '78 F.

I bought a crank with rods from a guy in the US and got him to send the crank directly to Big Jay rather than to ship one from Aust and then back here again.

Just having a look at the Honda microfiche, No.6 gives the 2 part nos for the bolts and No.7 the 2 for the nuts with images.
http://www.cmsnl.com/honda-cb750f2-supersport-canada_model14686/partslist/E15.html