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Discussion Starter · #1 ·
What way do you turn the screws to adjust the mixture? I am running a little rich and want to lean it out a little.
 

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Turn it in like you are tightening a screw to lean it out.
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Turn them IN (clockwise.)



R
 

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I started to say clockwise too. But I started thinking the same thing Rick.
 

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I thought from previous discussions they were backwards, more of an air adjustment screw.



So, in effect, they're like a regular needle valve that lets more fuel in if you loosen them (CCW) and less fuel in if you tighten them (CW) ?



I also seem to recall the starting point is 2-1/2 turns out
 

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I thought from previous discussions they were backwards, more of an air adjustment screw.



So, in effect, they're like a regular needle valve that lets more fuel in if you loosen them (CCW) and less fuel in if you tighten them (CW) ?



I also seem to recall the starting point is 2-1/2 turns out


I think as a rule of thumb, if the screws are on the air box side of the carbs, then they are usually an air adjustment screw and turning them in would result in a richer condition,,but if the screws are on the engine side of the carbs they are fuel adjustment screws and turning them in will lean the mix.

Yes 2.5 turns or so is a good starting point for adjusting the mixture.
 

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I've seen some posts on the old site about verifying your mixture by doing a spark plug color check, but if I remember right the color only reflects the last couple of seconds of running before the engine is shut off. Are there other good ways to check if the mixture is right? Infrared thermometer on the pipes, smog check, trial and error with gas mileage?
 

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1978 CX500 "The Grub", 1983 GL650I "Nimbus"
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Yes 2.5 turns or so is a good starting point for adjusting the mixture.
It depends on the model and year. Initial settings are in the FSM.



R
 

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Virtually the only time you will get a false reading of the spark plug colour is if you have just started the bike from cold.Check the plugs after a ride or take a plug spanner out with you and stop somewhere safe and check.



If ever you have the carbs off you may want to do the modification I have done,







I have ground off both sides as per the picture of the substantial carb bracket to allow easier access to the idle mixture screws and have ground an angle on a small screwdriver to use as an idle adjuster tool.













HTH
 

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Discussion Starter · #11 ·
Thanks guys. According to my feeling the pipes the left side is nice and hot and the right is medium hot. That might explain the hesitation.
 

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I've got a % oxygen analyzer around here somewhere but wouldn't know how it could be used.



Actually, if you hit a salvage yard and grab a set of old O2 sensors that have the heaters built in (they're usually the second ones, after the cats) you should be able to easily rig up your own mixture analyzer that can not only give direct readout but comparisons at the same time.



You'd need the sensors with the heaters since they wouldn't get into their operating range by placing them at the ends of the tailpipes so you'd need an auxiliary battery to keep them heated. Then comes a simple A/F gauge circuit which monitors the output of the sensors. It isn't a linear output, it constantly varies between 0 to 1V almost in a square wave so you integrate/average the sensor output and a 0.5V average indicates a proper mixture.



Sounds like a neat project may be in the works for the future, wonder if I still have my special O2 sensor socket hanging around somewhere so I can take it the next time I hit the auto salvage yard.
 

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Discussion Starter · #13 ·
I am going to borrow a color tune from a friend and get the mixture set right. Be nice to ride and not wrench on this thing.
 
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