carb swap....... i think??

[mattmf01]

I have 2 different ssets of carbs here, one from a 72 cb750 four and one from a 76 cb750 hondamatic, I want to put one on my 78 custom chopper, has a 78 cb750k in it..... bored once over. is this possible?

[shultz_1978]

Hi Matt

Not sure if they will. But I am sure that as long as they will line up and fit the intake boots you can make any thing work. If I am wrong one of the other guys will say so.

I my self have two 78's but am running stock year carbs. I think the 77 and 78 carb's are the only two years for these carbs.

Good luck.

[seestheday]

Pretty sure you should be fine as long as you're ok with fiddling with jets etc.

I think that all of the SOHC measurements were the same, but you might want to confirm (or someone else more knowledgeable about the SOHC's can chime in).  I do know that the DOHC and SOHC engines had different measurements so you'd have to make new manifolds if you wanted to switch them.

[shinyribs]

All SOHC 750 carbs will interchange. But not all boots are the same.

Roundtops have two different linkages. The very first set used four individual cables out of the top of each carb connected to a common cable back to the throttle control. All the rest of them used a push-pull cable setup and a lifter fork setup to operates the slides.

77-78 engine used keyholes carbs. They also had a separate choke cable where the roundtops had carb-mounted choke linkage.

The keyholes use different boots than the roundtops.

All the head stubs are the same so you just have to use whatever boots fits the carbs.


Roundtops

Keyholes

[mattmf01]

Great thanks, im going to figure out how to work the Key Hole style.

[Piute]

mattmf01 wrote

Great thanks, im going to figure out how to work the Key Hole style.

   Been real happy with mine Stk 77 F2 key-top's, have fun,

[Lucky 1]

The 1972 CB750 carbs will work the best.
If you have aftermarket exhaust and pods use #120 main jets and #42 idle jets.
Use needle clip position #4 counting from the top for the 7A's. and use needle clip position #5 for the 657's.

[TOOLS1]

Lucky 1 wrote

The 1972 CB750 carbs will work the best.
If you have aftermarket exhaust and pods use #120 main jets and #42 idle jets.
Use needle clip position #4 counting from the top for the 7A's. and use needle clip position #5 for the 657's.

I thought you were a Keyhole fan.
TOOLS