Swapping Carburetors CB750F to CB750K Keihin | Carb Clean & Rebuild | Honda Project | Part 17

Swapping Carburetors From CB750F to CB750K Keihin | Carb Clean & Rebuild | Honda Project | Part 17

In this episode, I cleaned and installed a set of round top carburetors to try on my CB750 project bike. These are the earlier style Keihin carbs from a CB750K, I'm replacing the CB750F carburettors that came with this bike in the hope to get it to run better. I am building this bike to be a road-going runner, not a full restoration.

Honda CB750 Carb repair kits I use: https://ebay.us/oF83mw

I have a set of PD carbs on the bike, but they are off a later model. It was suggested in the comments by Joe (Jose) that I might try a set of the correct round top carbs, due to possible differences between the earlier and later Honda CB750 engines in terms of compression ratio etc, so I decided to give it a go.

The carbs that I found were pretty gummed up. But once I started cleaning them they turned out not to be too bad. Apart from the seals, float valves and the pilot jets I used all of the original parts. I wanted them in working condition, so that was the focus of my efforts.

I set the floats to the standard 26mm, but despite this and the new float valves and seats and fuel filters, the bike does sometimes leak a little when you first switch the fuel on. Not always and not much, maybe it’s a normal thing, but I don’t remember it from the first time around with these bikes!

When I fitted the carbs I realised that the inlet rubbers are wrong, in that they are too short. Obviously, they are for the later carbs. The knock-on of this is that where the throttle cable is clamped is very close to the heads, and when I fitted the airbox, the rubber horns don’t seal into the box, they nearly an inch short. If I decide to keep these carbs on the bike I will buy the correct ones.

I also had to adjust the nipple on the pull cable, and the outer sheaf on the push cable. This happens every time for me. Maybe I am buying cables that are too cheap, or just using mismatched parts. There is another video on soldering the nipple to come so I can show you how that adjustment is done.

For more helpful how-to guides and restoration project logs, visit our blog: https://www.spannerrash.com/

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