Okay I will try to give the short version here... I bought my 2001 GS last summer and I rebuilt the carbs because the bike had been sitting for a while. I drilled out the brass caps over the mixture screws, and they seemed to be about 2.25 turns out on one, and 2.5 turns out on the other. I adjusted them both out another 3/4s of a turn, so they should have been around 3.0. and 3.25.

Recently, I noticed the bike having more trouble getting a steady idle (I was constantly adjusting the idle screw at stoplights), and the bike seemed to be even boggier at lower RPMs. So I readjusted the idle screws another 3/4s of a turn out, so now they should be around 4.00 and 4.25 (assuming they held their previous positions over 8 months and 3000 miles).

Now the bike feels muuuuuuuuuuuuch healthier. Idle is rock solid. Don't need the choke as long. I can ride somewhere, park it for a half an hour, come back and start it up without the choke. I could never do that before; the bike seemed to cool down far too quickly.

But there was one drawback.... the bike seems to have lost a bit of power at the top end. I am supposing that now the bike is running too rich at that range.

I am considering backing the mixture screws off 1/4 of a turn, and then call it a day. I am also considering backing them both all the way down and then resetting them so that they are equal.

Here are my questions:

1 - Can you lose upper RPM power from running too rich of a mixture?

2 - are there any other drawbacks of running the bike too rich?

3 - should I reset my mixture screws so they are the same, even thought they were slightly off from the manufacturer?

4 - how do you define "one turn" of the mixture screw? I always thought this meant 360 degrees, but a fellow motorcyclist is trying to tell me that 180 degrees is one turn.

bump... anyone?

sorry not to be more help but I run my bike 3 full turns out.  I have a K&N, rejet, and pipe.

Quote from: SixSpeedSquirrel on April 05, 2009, 08:10:29 AM


Here are my questions:

1 - Can you lose upper RPM power from running too rich of a mixture?

2 - are there any other drawbacks of running the bike too rich?

3 - should I reset my mixture screws so they are the same, even thought they were slightly off from the manufacturer?

4 - how do you define "one turn" of the mixture screw? I always thought this meant 360 degrees, but a fellow motorcyclist is trying to tell me that 180 degrees is one turn.

1.  The mixture screws have no effect on wide open throttle upper rpm power.  They only affect idle and small off idle throttle inputs.  

2.  Lots of drawbacks from too rich including plug fouling, carbon buildup, poor MPG.......

3.  A quarter turn difference between the two is no big deal.  

4.  One turn is 360 degrees

There is a correct way to set the mixture screws.  Just backing them out 3/4 turn at a time won't get you dialed in very well.  If you do a search here you'll find it.  4 turns out seems to be more than what most people end up with.

turn them both all the way in then back out equal amounts....play around with it.

Quote from: ineedanap on April 06, 2009, 03:23:18 PM

There is a correct way to set the mixture screws.  Just backing them out 3/4 turn at a time won't get you dialed in very well.  If you do a search here you'll find it.  4 turns out seems to be more than what most people end up with.

I am thinking that maybe my carbs need to be synched, and right now one is working harder than the other. Richening the mixture is helping to mask that a bit, but it's obviously not the right solution. Just a temporary fix for a guy without vacuum gauges

If you will pop the carbs off the intake,  You can see the butterflies.   You can get a pretty good darn synch by eye, just adjust both carbs to show an equal gap or crack at the bottom when closed with the screw near where the throttle cable plums into the carb.   Mine are adjusted this way to show just a hairline opening and the bike runs excellent.

woops, ignore this

You don't need vacuum guages.  You can do what commuterdude said, but you might find it easier this way.   

Get 5 feet of clear tubing that will fit on carb sync port on the top of the carbs. (1/4 inch?  I can't remember off hand but it's one of the 3 common sizes at the hardware store) 
Hold it like a U. 
Put a few ounces of oil in the tubing (until the oil fills up 12-18 inches of hose). 
Connect an end to each carb top.  
Let the U hang.   
When you start the bike the oil will move toward one carb or the other.  Turn the carb balance screw clockwise or counterclockwise until the oil stays in the middle.  Easy and cheap and nearly as accurate as those expensive gauges. 

Quote from: ineedanap on April 07, 2009, 04:23:03 AM
You don't need vacuum guages.  You can do what commuterdude said, but you might find it easier this way.   

Get 5 feet of clear tubing that will fit on carb sync port on the top of the carbs. (1/4 inch?  I can't remember off hand but it's one of the 3 common sizes at the hardware store) 
Hold it like a U. 
Put a few ounces of oil in the tubing (until the oil fills up 12-18 inches of hose). 
Connect an end to each carb top.  
Let the U hang on the ground.   
When you start the bike the oil will move toward one carb or the other.  Turn the carb balance screw clockwise or counterclockwise until the oil stays in the middle.  Easy and cheap and nearly as accurate as those expensive gauges. 

THAT'S COOL!  WILL HAVE TO TRY THAT SOMETIME!

I found it on a ninja website a few years ago when I had a ex250.   

I edited the instructions to read "let the U hang" instead of "let the U hang on the ground"  It can hang however it wants but you want the oil to be able to climb up the hoses. 

Also if the oil level gets too close to one of the carbs, just shut the bike off and wait for the oil to settle.  That's it, super easy and cheap.