Topic: 72 motor in a 78 frame

[robe0531]

hi i am rebuilding my 78cb750 motor and i want to keep riding i have a 72 cb750 motor with carbs will i be able to mount the 72 motor in the 78 frame so i can keep riding while i rebuild my 78 motor

[mkramer1121]

hi i am rebuilding my 78cb750 motor and i want to keep riding i have a 72 cb750 motor with carbs will i be able to mount the 72 motor in the 78 frame so i can keep riding while i rebuild my 78 motor

short answer, yes, long answer, you need to switch the exhaust stubs from the '78 to replace the spigots on the '72 if its an original exhaust

[Patrick]

I have a K2 750 engine in my 1978 F3 750 frame right now. It works fine. I used the F3 air box and the F3 carbs and the K2 exhaust.

Patrick

[robe0531]

awsome
thanks for the fast response
i love these forums

[Patrick]

Oh yeah, one other thing to consider. The K2 oil tank will not bolt up to the F3 frame. Yet the vent spigot on the back of the K2 engine is smallerr than the spigot on the F3 motor and the connection on the F3 oil tank is larger than the spigot on the K2 oil tank. The F3 oil tank has only one vent instead of two like the K2. So you will need a reducer in the oil line from the tank to the engine. No big deal, but it is a difference.

Patrick