Topic: 350F jetting

[steve]

I am rebuilding the carbs on a 1973 CB350F.  The bike will have a 4 into 1 exhaust and stock airbox.  Any recommendations on jetting?
Also: If I were to go to air pods -   any air pod and jetting recommendations?

Thanks

[Nurse Julie]

Personally, if you stick to standard air box, I can't see it needing re jetting. I have fitted a 4 into 1 delkevic on one of my 550's and a 4 into 1 1970's Yoshi on another of my bikes and they all run great with the original jetting set up. I can't see why a 350/4 would be any different 🤔🤔🤔🤔.

[carnivorous chicken]

I'd stick with stock and keep the airbox. I've used 400F 4-1 systems on a few 350Fs with no need for rejetting. I've rejetted my current 350F (with 400F system) but only because of altitude -- I am at 2500 meters.

[steve]

Good feedback. Thanks

[carnivorous chicken]

I should add: keeping the stock airbox means that removing the carbs is a PITA. Replacing the float bowl screws with allen head ones means that if you have an issue -- clogged jet, e.g. -- you can drop the bowl with the carbs on the bike to inspect it. And when you have the carbs off for rebuilding, make sure everything's done correctly the first time before mounting them because of the PITA factor.

[HondaMan]

I'll echo the others: keep the OEM airbox and jetting. There is no need to rejet these tiny jets unless the cam is changed, and even then most of the time it stays fine - so long as the airbox is kept in place. Without it, you will never get it jetted right again to run the 10,000+ RPM this engine can do.

The length of the bike (all the SOHC4 bikes, for that matter) is too short for the exhaust pipe length to cause need of rejetting. Outside of the special Mike Hailwood 250cc Six's megaphones and the super-long Dunstall 4-2 headers for the 750, there haven't been exhausts that made significant increases in power, nor carb jet change requirements. Briefly, in 1974, there was a single 4-1 header for the K3/K4 750 that added a couple of HP at 7000 RPM, but that was it. It also hung so tightly around the oil filter that you had to remove the pipes every time you wanted to change the filter, so it didn't stay around very long.

[steve]

Good info.  Thanks.  I did purchase new rubber for both sides of the carb which should help with assembly.  Just to clarify - #35 & #75 is considered stock jetting, correct?

[HondaMan]

Good info.  Thanks.  I did purchase new rubber for both sides of the carb which should help with assembly.  Just to clarify - #35 & #75 is considered stock jetting, correct?

Yep, that's it. All of the rebuild kits for these carbs that I have seen supply larger jets (#40 and #80), which makes the bikes blacken plugs and have a host of throttle-control issues. They are, after all, just 85-ish CC engines, so they don't drink very much!