Topic: Old carbs, newer motor

[beemerbum]

I'm thinking of mounting  older round top carbs to a 1977 CB 750 motor. I realize the rubber parts are likely different. Has this been done? What parts would I need to source to do this?

[Shtonecb500]

you shouldn't need anything.

[Scootch]

1 to 4 throttle cable?  Older style twist grip?

[newday777]

I'm thinking of mounting  older round top carbs to a 1977 CB 750 motor. I realize the rubber parts are likely different. Has this been done? What parts would I need to source to do this?

Yes.
Intake boots and throttle cables are different but can be changed over. I put my K5 carbs on a K8 to test run it.
If K4 and earlier then you need to put a fuel T on and reroute the fuel lines to the left side petcock.

[beemerbum]

1 to 4 throttle cable?  Older style twist grip?

No, my carb rack is the 2 cable push pull style.  I anticipate a problem with the carb to head boots. The old carb boots look like they wont fit on the '77 head.

[Mr. Mike]

I had this done to my ‘78 CB750.
The guy who did it knows his stuff. ‘74 Round tops. IIRC, I had to get proper isolator boots, an earlier air box and the boots for that too. All bolted up like it was designed. I still use the original two cable push pull. Toughest part was sourcing a new air box gasket. Found a gasket material nearly identical in dimension to OEM on Amazon and siliconed it in on one half.