Topic: Mixture screw question

[JDrider]

Hi everyone,
I've owned this 1975 cb550K1 since last october, stock except for a 4 into 2 exhaust that is almost as old as the bike.
It runs good (after many leaks and electrical repairs).
Now I'm turning my attention to the carbs.
I happen to notice that my mixture screws are a half turn out on all.
What does this mean? What will moving them to 1 out or more do?
I figured I'd ask before going down this rabbit hole.

I will be pulling the carbs at some point because I an getting some gas in the oil.
Thanks,

[TwoTired]

The pilot screws set the mixture for idle throttle position.  Turning them outward changes the engine pick up response under load when given a throttle twist.  The more outward you turn them , the more stumble you will encounter with throttle twist at low RPM.
The more inward you turn them the more likely to soot the spark plugs during longer idle periods.  I’ve found the stock one or one and one eighth turns setting to be a good balance point where you can twist the throttle up to half travel in any gear at low Rpm under engine load and still get reliable pick up, if not particularly quick.  If you want quick, use lowest gear and as the engine gets past 3-4K Rpm use as much throttle as you want.

[JDrider]

I just want to make sure the P.O. didnt mess this up like they messed up other things on the bike.
So I should make them all 1 turn out or more and see how that is, or leave them alone?

[robvangulik]

Why not simply try it, its easy to set back to the previous setting!

[JDrider]

Why not simply try it, its easy to set back to the previous setting!

I will do this, I just didnt know if there would be a reason it was set that way.
I dont know much about the carbs, but will be learning.

[PeWe]

A ride with screwdriver in your pocket, stop, adjust, ride, stop again to adjust.... will help to find out.

I have learned the hard way to always gently close until screw stop, from here open as needed.

If starting from a specific minimum setting and adjust +1/8 each time will often end up in different settings for the carbs.

[Scott S]

 And just so you know: as a rule of thumb, if they're on the air box side of the carbs, they control air. In reduces air in the mixture (richer), out adds air (leaner).

 If they're on the engine side, they control fuel. Same principle as above, but in cuts fuel (leaner), out adds fuel (richer).

 If you have the stock '75 carbs, yours control the amount of air in the mixture.

[JDrider]

Good to know, thank you.

[dave500]

keep the motor over 3000 rpm,wont matter then,dont be lugging it,dont be scared of high rpm at all on these!

[TwoTired]

keep the motor over 3000 rpm,wont matter then,dont be lugging it,dont be scared of high rpm at all on these!

So true, if you want any significant power from the 550 motor.  The red line is high for a reason.  Use it.

[dave500]

even in 35 mph traffic stay in 3rd/4th,keep it "on the boil"ready to peg it and scoot away if you need to.

[Floshenbarnical]

Yeah it was a real learning experience for me discovering how these bikes enjoy higher RPMs

[mr.brandon]

I noticed that nobody had mentioned looking at your sparkplug is often a very good indicator of where the air/fuel mixture screws need to be set.. if you pull the plugs and they are black this may be an indication that your screws are turned to much inward. If too white or rather white at all (lean), too far turned out. The latter (lean), being a much worse running condition for your engine as, this will produce way too much heat and do bad bad things. Sparkplug condition or color will not always be directly linked to your air screws.. however, it can certainly play a big role. I would check your plugs after a decently long ride having used ALL throttle positions (there are youtube videos on how to do this properly).. also, the your carbs have been synced to each other correctly, I would assume?