Topic: 73 CB350 Throttle Adjustment

[brendanpk]

I have a 73 CB350 which now has clean carbs, stock airbox and kei hin carburetors. After putting the carbs back on after a needed cleaning, I'm not sure how the throttle should be adjusted. My bike will ride fine for about 10-15 minutes then chokes out pretty easily. I'm sure the mixture is probably rich from what I have read on the forums, but I still have a question for which I could find no answer. Should the throttle plate be  adjusted so that it is completely shut in the carb or slightly open for airflow? Good sense tells me that it should be shut, but it won't idle correctly when it is adjusted that way, so I am reaching out past my hometown mechanic friends to find out some more feedback. Thanks for any and all responses!

[kslrr]

The closed position of the throttle linkage and the slides is adjusted by the idle speed knob.  The throttle cables are then set at the required slack.  Do you have a shop manual?

[brendanpk]

No, I don't have a manual, but I did make sure the scews that move the throttle arm were just barely touching after i let it snap fully shut. Is that what you are refering to? But more to the point of answering my question, should they be slightly open or completely closed?

[Gordon]

I think you need to clarify what you mean by "throttle plate".  Are you talking about the choke valves or the cylindrical throttle slides? 

[brendanpk]

The flat plate that sits inside of the carburetor on the engine side. It is connected to the metal dowel that slides through the carb which the throttle cable hooks into on one side and has the arm with a screw/spring on the other to adjust the the arm up or down. Basically, the plate in the carburetor, on the engine side,  that opens when you open the throttle and closes when you close the throttle. Maybe that was too descriptive, but I am very new to this, so my terminology may be off a bit.

[Gordon]

I'm still not following you 100%.  The only flat plates that should be in your carbs are the choke plates.  The throttle slides are cylindrical, and they're the parts that slide up and down with the movement of the throttle grip. 

If that's what you're talking about, then there will be a very small opening at the bottom when the throttle is completely closed.  This allows enough air in for the engine to idle.  You don't need to measure or set this gap, though.  Adjusting the idle stop screw to get a good idle speed when the engine is warm will take care of that. 

[hoodellyhoo]

Is your bike a 350 Twin or a 350 Four? I'm guessing it's a twin because then it would have the valves you describe because it has CV carbs.

[brendanpk]

My apologies, it is a twin. I suppose I could have mentioned that. So, with that in mind, should the plates be completely shut or adjusted so it idles around 1500?

[DollarBill]

http://forums.sohc4.net/index.php?topic=17788.0  There is a CB350 Manual in here somewhere.....

I have a 73 350 twin and if I recall the throttle slides should be open a little bit.  I haven't looked at them in a while but I think almost all carburated motorcycles require a little opening for the idle.

[Green550F]

the butterfly throttle plates will need to be open slightly in order to idle.