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Carb knowledge?

  • Thread starter Thread starter IOWA450T
  • Start date Start date
I

IOWA450T

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I have to preface this by saying I am not normally a moron....
I bought a Colortune over the winter and since the weather was condusive to riding today I got Rita out (1981 GS850G) and pulled the tank and started "playing with my new toy. I really should have done a little research first I now realize. Not really having any idea what I was doing I started adjusting the only screws I could see (I think they are air screws, on top, engine side of the carbs). Nothing I did seemed to make any difference in the combustion color; it stayed a pretty steady blue with an occasional yellow flash. To make a long story short, I wasn't really paying close attention to what I was doing and lost track of how far I had turned each so I don't think I got them set back to where they were; I had to turn my idle up to about 1500 to keep her running. Took it for a ride and acceleration seems to be quicker than before but vibration seems a little higher; possibly my imagination but there seemed to be more valve train noise when I got home and took my helmet off. I drove about 30 miles. I guess my question is this: are there standard settings for these screws that I should attempt to set them to or some method I can use to make sure I have them right? I am really a novice where carbs are concerned and probably should have asked before fiddling but you know how it is when the sun comes out and you have a new tool to try out... any knowledge out there I can tap in to?
 
You should reference a manual but if you are talking about the pilot mixture screws then usually they are 1 1/2 to 2 full turns out. I would try carb #1 and carefully turn clockwise(in) and count the turns til it doesn't turn anymore(Don't force it!!). I use only two fingers to be sure I'm not muscling it too much. See if it is about 2 turns to close it and now turn it out 1 1/2 turns. Do this for each carb and write down how many turns they were originally out to get a starting point to go back to if you mess things up. But you will wind up with all at 1 1/2 turns out for the first test. You might have to then add a 1/2 turn (2 total) to all to see if it runs better.
 
Hi,

From my little BikeCliff website, here is one suggested procedure for setting the pilot screws:[FONT=Helvetica,Arial,sans-serif]

The Highest RPM Method (by Mr. psyguy)[/FONT]
  • Take off the tank.
  • Set the pilot screws at 2 turns out.
  • Warm up the engine and let it run.
  • Adjust the idle to approx. 900 rpm.
  • SLOWLY turn the screw at carb #1 in - at some point the rpms are going to start dropping and the engine wont run as smoothly.
  • Start turning the screw back out while you get the highest rpm read and a smoother sound from the engine.
  • At some point, turning the screw out further won't make any difference (and even further out may again take away the smoothness and the rpms).
  • You want your screw turned IN as much as possible without affecting the rpms/smoothness.
  • Re-adjust the idle to 900 rpm.
  • Stop the engine to let it cool down a bit or place a big fan in front of the engine and do this while the outside air is cooler (morning/winter).
  • Proceed with carb #2.
  • Repeat steps 4 through 10 as necessary for all carburetors.
  • When complete, re-adjust the idle knob for the correct rpm as per your factory manual (usually 1050 rpm +/-100 rpm). In any case, do not idle below 900 rpm as this may result in insufficient oil flow.
Thank you for your indulgence,

BassCliff
 
I found the carbtune to be more of a problem than a solution. I used it on my 85 GS550 and spent a lot of time adjusting the air screws with no great improvement.

I've since used the spark plug chop to provide better results.
 
Me, too!

Me, too!

gaillarry said:
I found the carbtune to be more of a problem than a solution. I used it on my 85 GS550 and spent a lot of time adjusting the air screws with no great improvement.

I've since used the spark plug chop to provide better results.
Click to expand...

Me, too! I bought one and think it was a huge waste of money; a total gimmick. I used it once and, if anyone wants one, mine is for sale...cheap!
 
gaillarry said:
I found the carbtune to be more of a problem than a solution. I used it on my 85 GS550 and spent a lot of time adjusting the air screws with no great improvement.

I've since used the spark plug chop to provide better results.
Click to expand...

yeah, me too! i can do it better than the colortune just by using my EARS :-s

however, the old elect system would be contributing A LOT to the "bad" colortune readings, i should imagine
 
BassCliff said:
[FONT=Helvetica,Arial,sans-serif]The Highest RPM Method (by Mr. psyguy)[/FONT]
Click to expand...

wow, i'm getting quoted now
surprise.gif
 
If you turn the screws all the way in it doesn't turn the flame yellow? If not your o-rings are ate up and you need to get new ones.
The colortune set my pilot mixture too lean and I had to come out another turn or so. It's great for a ballpark setting but you can do this with the highest rpm method which I use.
 
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