Topic: running rich, adjustment screw

[78_SaltLick]

so i am clearly the dumbest person on this board when it comes to bikes, so my question im sure will be laughed at, but i have to ask it.  My bike runs good without an air filter, runs great. put one in and it runs way too rich, black smoke comes out of the tailpipe when you really gun it, it spits and sputters at slow speeds. This is with a new K&N filter, and a recent tune up. So this means the carbs need more air, correct?  Is this a case of the carbs needing to be rejetted or the air/fuel mixture screw needing to be turned to lean it out? If its the screw, where is this screw and how should it be adjusted  i have a 74 cb550. Ive heard alot of stories on this board that leaning out the mixture will correct the issue i am talking about, i would love to give it a try if its as easy as turning a screw, where is this screw? Is it only one, or are there 4, one for each carb? How far in or out do you turn it? thanks again.

[csendker]

i am clearly the dumbest person on this board

Angling in on my territory? 

So this means the carbs need more air, correct?

Assuming you want to normally run with the filter installed, I think it's actually less fuel that you want as the air quantity will be somewhat fixed.  Typically, that means rejetting, or maybe fooling around with the needle clip setting.  There is an air bleed adjustment screw that should be set to 1-1/8 turns out (from gently seated) for a stock set-up if I recall correctly.  Your air filter type (or pods) and exhaust all play into the air/fuel settings.  This thread will surely bring in some experts for better advice though.

[TwoTired]

Look on page 109 or 113 of the Clymer manual (M332).  Idle air bleed adjuster screws are depicted.
However, there is only one screw on the side of the carb body.  1 & 2 carbs have it on the left, 3 & 4 carbs have it on the right. These screws are spring loaded to hold set position.
Insert a slot matching screwdriver and turn each clockwise until gently seated, counting the number of turns.  Setting them is the reverse.
The stock setting is 1 1/2 turns out from closed, plus or minus 3/8 of a turn.  Each carb should have the same setting.  If you want to lean the idle mixture, turning them out counter clockwise will increase the amount of air mixed with the fuel, making it leaner.
Given your bike's symptoms, add 1/2 a turn to whatever your current settings are, and drive for effect.  There should be some improvement.  If not enough keep opening the screw on each carb in equal increments, and retest.
At three to five turns out, the screws become less effective at change.  If your engine response is still not improved by then, other changes inside the carbs Will be needed.
Yes, it is possible to go too far.  On a stock bike going to far will make throttle response poor so that only very small changes in throttle position are accepted.  Also, the screw springs may become ineffective and not hold the screws where they were set.  There should always be some resistance to setting changes felt through the screwdriver.

Cheers,

[78_SaltLick]

Look on page 109 or 113 of the Clymer manual (M332).  Idle air bleed adjuster screws are depicted.
However, there is only one screw on the side of the carb body.  1 & 2 carbs have it on the left, 3 & 4 carbs have it on the right. These screws are spring loaded to hold set position.
Insert a slot matching screwdriver and turn each clockwise until gently seated, counting the number of turns.  Setting them is the reverse.
The stock setting is 1 1/2 turns out from closed, plus or minus 3/8 of a turn.  Each carb should have the same setting.  If you want to lean the idle mixture, turning them out counter clockwise will increase the amount of air mixed with the fuel, making it leaner.
Given your bike's symptoms, add 1/2 a turn to whatever your current settings are, and drive for effect.  There should be some improvement.  If not enough keep opening the screw on each carb in equal increments, and retest.
At three to five turns out, the screws become less effective at change.  If your engine response is still not improved by then, other changes inside the carbs Will be needed.
Yes, it is possible to go too far.  On a stock bike going to far will make throttle response poor so that only very small changes in throttle position are accepted.  Also, the screw springs may become ineffective and not hold the screws where they were set.  There should always be some resistance to setting changes felt through the screwdriver.

Cheers,

When you say "add 1/2 a turn to the current settings" do you mean turn the screws clockwise or counterclock wise?

[TwoTired]

Counter-clockwise

This will make the throttle from idle to about 1/4 open position, leaner.

[78_SaltLick]

thank you kind sir, i did find the screws right where you said they were. i do believe they are off, i can just look at the slot position on the screws and tell they are in different positions, on one side the slots on the screw heads are straight up and down, other side they are sideways.....these are all suppose to be backed out the same amount of turns right? would you suggest in this case i seat them all the way in, and then back them out or leave them as they are like you said, and back them out?

[paulages]

they probably wont all be in the same exact position when they lightly seat, and thus won't all look exactly the same. a better measurement if you're looking for better consistency might be with a dial indicator, measuring each screws depth against each carb body. does this sound reasonable lloyd? i do think lightly seating them then running each out an equal number of turns should suffice though.

[78_SaltLick]

i just backed them out 1/2 turn, its 1am here now, neighbors will go nuts but what the hell i have to try it out now....hey paulages this is dave i talked to you a while ago via email from oregon whats up man. see ya around.

[TwoTired]

they probably wont all be in the same exact position when they lightly seat, and thus won't all look exactly the same. a better measurement if you're looking for better consistency might be with a dial indicator, measuring each screws depth against each carb body. does this sound reasonable lloyd? i do think lightly seating them then running each out an equal number of turns should suffice though.

Paul, if you want to expalin to Dave how to obtain, mount, and use a dial indicator, I won't hold you back.  However, I feel screw thread pitch is plenty accurate and predictable w.r.t. air bleed settings.

I'm trying to figure out why Dave completely ignored instructions for determining his current Air bleed screw settings, and decided to simply change what it has, right or wrong.

The hole seat depth may be different from carb body to carb body.  Further, the screw slot placement in the screw head is NOT calibrated from screw sample to sample, therefore comparing screw slot positions between carbs is meaning less.  To find their adjustment position, you have to count the turns out from seated on each carburetor.

[78_SaltLick]

they probably wont all be in the same exact position when they lightly seat, and thus won't all look exactly the same. a better measurement if you're looking for better consistency might be with a dial indicator, measuring each screws depth against each carb body. does this sound reasonable lloyd? i do think lightly seating them then running each out an equal number of turns should suffice though.

Paul, if you want to expalin to Dave how to obtain, mount, and use a dial indicator, I won't hold you back.  However, I feel screw thread pitch is plenty accurate and predictable w.r.t. air bleed settings.

I'm trying to figure out why Dave completely ignored instructions for determining his current Air bleed screw settings, and decided to simply change what it has, right or wrong.

The hole seat depth may be different from carb body to carb body.  Further, the screw slot placement in the screw head is NOT calibrated from screw sample to sample, therefore comparing screw slot positions between carbs is meaning less.  To find their adjustment position, you have to count the turns out from seated on each carburetor.

ha ha !! i told you im the dumbest person on this board, i had to prove it to you all. I didnt ignore it, just misunderstood you. i went off of this statement "Given your bike's symptoms, add 1/2 a turn to whatever your current settings are, and drive for effect" so current settings i thought you meant leave them where they are at, and back it out. Possibly what you meant was return the settings to stock (backed out 1 1/8th turn, then back it out 1/2 turn more? Anyways i took it for a test run after backing it out a half a turn, and it took care of the problem. Seems to be colder to warm up (before it warmed up too quickly) but once its warmed up it runs with no hesitation at all now. Your the man TwoTired! Thanks again guys!

[78_SaltLick]

im tempted to return the settings to stock, then back it out 1/2 turn now that i know what you really meant Two Tired, but since its running good i am scared to mess with it.......

[paulages]

glad to hear of the fix.

yeah, tt i didn't really think the dial indicator was neccesary or even neccesarily a good gauge of equality between the settings. i figured the screws are probably all the same length, and the bodies all cast to the same depth, but the threads probably all set at a different start point, making the relative position of the slotted head irrelevant, but the depth possible more accurate. in any case, as i said iv'e never had any problems using lightly seating and counting the turns. sure no point in overdoing it for nothing. 

[Dusthawk]

And this is a perfect example of why I love this forum!!!!!!!

Thank you yet again TT for your excellent advice. I've been having a few probs in this area myself and your concise and accurate info cleared the webs once again!!!

I will forever be grateful to these forums and those who post for the knowledge passed along!!!

Peace and Long Rides,

Jeff