Topic: Carb Issue 73 Honda CB350F

[Kyle56403]

So first off I'm extremely new to carburetors engines and 4 carbs is daunting and complicated but the issues that I'm having are as follows.
First if all i cleaned the carbs and did a simple bench sync using a 5/32 drill bit to set the slide height at idle and got the carbs on the bike and started it and well it would run but if the choke was open then the engine would start to sort of run away and rev higher than i was comfortable with so i would close the choke to almost fully closed and it would run stable a little rough but it wasn't running away like it was before and if i fully closed the choke the engine would shut off, not sure how or why as I've read that during normal operation you want the choke open, but that's only the first problem secondly anytime i tried to give it any throttle the engine would die. Any help on either of these issues would be greatly appreciate.

[jaytee-nz]

I have no experience with CB350 carbs specifically but I'm pretty sure all Honda fours behave in a similar way i.e. you need the choke to start the bike from cold and they take a few minutes to warm up before you can start to ease the choke off. You can't start the bike and expect the engine to immediately idle well without the choke on, if it is cold.
The high revving may be due to a vacuum leak. Have you renewed the o rings in the carb manifolds to get a good seal ? Also check that all the carb related clamps are tightly secured and the four rubbers connecting to the manifolds are not cracked or split.
The pilot jets will block easily due to their very small size. When you say you "cleaned the carbs" did you clean all the jets (especially the pilots) so that you can see through the holes and check that the internal passageways inside the carbs are not blocked ?

[denward17]

When you performed the bench sync was the idle screw backed off all the way?

[jpschroeder]

secondly anytime i tried to give it any throttle the engine would die. Any help on either of these issues would be greatly appreciate.

This generally is due to lack of fuel. Basically when you go wide open there is too much air vs fuel and the engine runs over-lean and dies. Check your fuel/air screws — lots of mixed reviews out there on what it should be set at but 1 full turn out seems just right for my CB350F (out = lean, in = rich). If i had to guess — I would assume your main jets are not getting enough fuel. The other thing you can check, if you pull the slides out, is what position the c-clip is at the top of the needle. Most folks seem to run those in the middle from what i can tell (for stock jets).

Also, what kind of airbox do you have?

[carnivorous chicken]

Could be air leaks, but could also simply be an idle set too high. If you start it with the choke closed and open it, and the revs start to take off, back off the idle adjustment screw and bring the idle down -- see if that works.

[Gibbon]

Hello.

My first guess would be the idle is set too high. 5/32" is much larger than I would use. I set mine using a 1.5mm drill (aprox. 1/16").