Topic: k engine in F2

[vaskeet]

Any fitment or other issues with putting a K engine in a 78 cb750F I understand carbs may need to be rejected

[bryanj]

Exhaust fitment, one has spigots the other studs, split collars and different clamps

[Jerry Rxman Griffin aka MuthaF'er]

Depends on which K engine. Pre 77 will need to have the front sprocket offset dealt with. +10mm difference in your F2.

[70CB750]

I put 78SS engine in K3 frame - no issues. 

[vaskeet]

Depends on which K engine. Pre 77 will need to have the front sprocket offset dealt with. +10mm difference in your F2.

do you have a engine SN breakdown to show when engine was made. There is a engine (only) for sale near me and I was thinking about getting it as a spare

[HondaMan]

The 'quick test' is: look at the countersprocket's shaft on the engine you wish to install in an F2/3 frame to see if it has a 'stepped' end on it for mounting the sprocket. If so, that one should fit OK.

Another 'quick test' if the sprocket is on that shaft (so you can't see the shaft end): if there is a single (center) bolt and a big washer holding the countersprocket onto the end of the shaft, it is most likely a 630 chain-size sprocket, which will likely drop into your frame with no grief.

The earlier engines have 2 small bolts (6mm, with 10mm heads) that hold a locating plate (oval shape with big hole in the center) that captures the sprocket in a floating manner on the countershaft. These are all a smaller chain size (530/50). This shaft will be shorter than the one found in the F2/3 engine arrangement, causing chain-alingment problems.