Topic: 82 cb650sc vb44c pilot screw adjustment help

[cmouta]

I tried to dial in my mixture today following the clymer manual and I think I'm an idiot. Can I explain what I think the manual is telling me? It seems like I'm just riching the hell out of my engine and running it hot.

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3. Lightly seat pilot screws, 1.5 turns out
7. Set idle to 1050+-50 with idle adj screw
8. Turn each pilot screw out 1/2 turn from step3 setting. (All of them???)
9. If speed increases by 50rpm or more, keep turning out by a half until rpms drop by 50( why would it eventually drop 50rpm if i keep enriching it? Wouldnt i just achieve max idle? again, all four at once? I was doing all four at a time and speed kept increasing and the oil I'm leaking from head really starts smoking so I quit and go back to 1.5turns)
10. Adjust idle screw to 1050rpm (if I'm supposed to be doing Max idle 1 at a time, do I do this after each Max idle Carb adjustment or after all 4 reach Max idle)
11. Turn no.1 pilot screw in(lean) until speed drops 50rpm
12.turn out 1 full turn
13. Adjust idle to 1050
14. Repeat 11-13 for other carbs

[tomkimberly]

The idle screw on the VB44 carbs meters the air, not the fuel.

As a rule of thumb, idle screw in front of carb, air metering, idle screw at rear of carb, fuel mixture.

On my 650C, I did a bench sync using 1/8" drill bits, set the idle screws to 2-1/2 turns out, and left it at that. It runs great.


Tom

[cmouta]

The idle screw on the VB44 carbs meters the air, not the fuel.

As a rule of thumb, idle screw in front of carb, air metering, idle screw at rear of carb, fuel mixture.

On my 650C, I did a bench sync using 1/8" drill bits, set the idle screws to 2-1/2 turns out, and left it at that. It runs great.


Tom

Thanks for the input Tom.  I've read so many different things on the topic, I must have gotten mixed up somewhere but that makes sense.  Turned the screws out, more air, leaned out the engine, started running hot.  I could have sworn though that, generally, pilot screw on the engine side = fuel mixture adjustment.

from the carb faq:
"What happens when I turn the airscrew out - richer or leaner?
If your airscrew is on airbox side of carb, turning out will lean mixture; opposite if airscrew is on engine side of carb. "

my VB44C's being on the engine side, turning them out would allow more fuel and run richer which i think is confirmed in the '82 high altitude adjustment supplement of the clymer manual which has you turn out .5 turn from lightly seated initially, resulting in a leaner condition.


honestly I think the bike has been running fine since i got it running with the initial 1.5 turns out but I know so little about bikes I want to make sure it's as perfect as possible.  Maybe I'll go for a good ride and pull the plugs and check them.