What are all possible causes of rich-running condition?

[bgk]

This post is a follow-up to my previous post titled ?No O-rings on my CV carb fuel mixture screws?.

I continue to be baffled by a rich-running condition in my 1980 GS1000G at low throttle settings. During the past two months I?ve carefully cleaned the carbs, replaced mixture screw O-rings with new, inspected mixture screws, replaced float valve and seat assemblies with new, checked float levels, replaced petcock with new, cleaned and flushed the fuel tank, replaced plug caps with new, checked coils, igniter box, and pulse generator.

Right now, my fuel mixture screw settings are:

#1 - 1/2 turn out from lightly seated
#2 - 3/4 "
#3 - 3/4 "
#4 - 7/8 "

I've got the main idle knob adjusted to get 1100 RPM at idle, hot with no choke.

Yesterday, on the advice of my friend and fellow GSR member Shaunt (ard) I removed the air filter from the airbox, replaced the airbox cover and went for a ride for half an hour. The bike ran just the same without a filter, as with the filter, which is to say it ran fine at commuter speeds and at engine RPMs generally around 3000 to 4000 RPM with occasional idling at red lights, etc. The plugs lightened up just slightly without the filter. I had been of the understanding that GS bikes run like total crap without an air filter, and particularly run like crap without a filter at RPMs above approximately 3000 RPM.

So, my question is:

What are all the possible causes of a rich-running condition, particularly when the bike runs rich at low throttle settings around town, but runs fine at all throttle settings and the plugs lighten up just fine after 10-minutes or so at highway speeds?

[Anonymous]

Are you running stock pilot jets?

[Hoomgar]

Clogged air jets?

Something did not get cleaned out right when the carbs were cleaned?

Pilots are way too rich? Maybe not what they appear? I have seen stock pilots drilled out by others and therefor the number on them is useless.

Are you sure the valves (specifically on the intake side) are adjusted within tolerance?

This is a head scratcher buddy

[bgk]

Yes.

Stock pilot jets, and stock main jets.

Also, I synched the carbs about a month ago with a Morgan Carb Tune.

It's possible that a previous owner drilled out the pilot jets or main jets, but I don't see any evidence of that.

[Hoomgar]

Yes.

Stock pilot jets, and stock main jets.

Also, I synched the carbs about a month ago with a Morgan Carb Tune.

It's possible that a previous owner drilled out the pilot jets or main jets, but I don't see any evidence of that.

Did you recently replace those pilots Brion? If they are the same ones that were in it when it ran right then I wouldn't suspect that. But if you replaced them when you cleaned/rebuilt the carbs then I would. See if you can at least confirm them.

These are CV carbs so are you 100% sure the air jets are right size and open?

[bgk]

The jets are the same jets that came with the bike when I bought it.

They have been removed, inspected, size numbers noted, cleaned, and reinstalled in the carbs three times now, since I've owned the bike.

I'm now going to go with your theory about the air jets and will pull the carbs off the bike again, hopefully this weekend.

I must be straightforward and clear to point out that when I say I cleaned the carbs, I have cleaned parts of the carbs, basically everything I can disassemble without actually pulling the rack apart.

[Hoomgar]

I think your going to find it then Brion. It sounds like something is clogged. Pulling them and inspecting them will most likely reveal it. Heres to a quick success!!

[flyingace]

It's a shot in the dark, but are you checking all 4 plugs to determine the over-rich condition or just 1? Seems like a dumb question, but we've had a raft of over-rich problems on the #4 carb on these old bikes.

[KEITH KRAUSE]

Shoot the two air jets/passages with carb spray cleaner. You'll see them on both inner sides of the carb, filter side.
These commonly "varnish up" and plug/restrict sooner than most other parts.

[bgk]

Thank you all for your responses.

Flyingace, yes I have been checking all four plugs. The bizarre irony is that my most of my carb work in the last two months was originally focussed on #4 plug getting dark colored, and I believe that I fixed that problem when I found a bent float pin in #4 carb, as I posted a few weeks ago. Yesterday afternoon and evening, I rode for about 150 miles with my GSR friend Shaunt (ard). The ride was ? hour interstate highway, then 2 hours sightseeing on suburban roads mostly at low/medium throttle settings in 3rd and 4th gears, and then another ? hour interstate highway. I checked the plugs three times yesterday. Currently, my symptoms are #1 plug staying dark-colored at highway speeds, while the other three plugs lighten up at highway speeds, yet all four plugs get/stay dark at lower speeds on the back roads. I?m still only getting 30 miles per gallon, mixed highway and back roads.

Mark and Keith, I intend to look at the air jets this weekend, but Keith?s post has me a little confused. I remember only one air jet in each carb, not two. I looked through the Carb Cleanup Series photos on the GSR this morning, and I still only see one air jet per carb.

What am I missing?

Also, I had thought that ?varnishing? came from fuel, not from air. What causes varnishing in the air jets?

Finally, can I just remove the air box to get enough access to remove the air jets, without having to pull the carbs off the bike?

Thanks again for your help. This problem is driving me nuts. September is the best month of the entire year to ride a motorcycle in New England, and I?d really like to resolve this thing and get on with enjoying riding my motorcycle, rather than screwing around in the garage.

[KEITH KRAUSE]

Varnishing happens from fumes also. There's always a film of fuel ready to dry every time you turn the motor off. If you have any leaking float valves or whatever to make the bowl levels higher, the fumes are worse.
The air jets, which are at about 5:00 and 7:00 are in a good place for fuel to run down and collect. Your '80 CV carbs should have two. A primary air jet and a pilot air jet.
If you remove the filter housing, you may be able to shoot some carb spray in them, but removal is of course best. Both of yours should be removable. Sometimes the pilot air jet isn't removable. Trying to remove them on the bike could be asking for trouble. I've actually never tried. I always put carbs on the bench when I do anything to them, except some bowl work.
30 mpg could actually be from one carb messed up, but could be a combination of things too. Hard to say, even harder if you don't know the carbs history.
Your road test results at highway and backroad speeds could be changing vacuum levels...dirty carbs...float levels...worn jet needle/needle jets...wrong jets...
If all the plugs darken more at lower speeds/throttle position, this would suggest the pilot circuit is dirty or rich and a small chance the choke plungers are not closed/leaking. Check for plungers seating fully before the choke is completely pushed off (proper slack). Obviously, as you test at highway speeds the jet needle is doing most of the mixing. If three plugs then look OK this again suggests the pilot circuit and/or primary air jet. Having one plug remain dark could still be any of the above.
You did say all four plugs have a good blue spark in a dark area?
And why are your mixture screws all set under 1 turn out? Did you adjust them for highest rpm or are they set "leaner" trying to beat this rich problem?

[bgk]

Keith,

Thank you for your excellent explanation of the varnishing condition and other possible problems that may be contributing to the plug color symptoms.

Yes, I have set the mixture screws ?leaner? to try and compensate for the problem. I did this partly because, in a previous post Earl Fornes noted that the mixture screws on his 1150 are set at around ? turns out.

This weekend, I will follow your advice and pull the carbs off and work on them on the workbench, rather than try the lazy way of just pulling the filter box off and spraying carb cleaner into the air jets. This will be the first time that I will have the carbs off the bike by myself, without an experienced GS mechanic friend nearby to look over my shoulder and help me.

I am not a motorcycle mechanic, and I don?t intuitively know what to look for or what to do, but I can follow directions and use tools properly. Your advice and the advice of others on the GSR have really helped me. Thank you.

[KEITH KRAUSE]

OK. Use good fitting tools and don't force anything. It's generally best to remove any small part and clean and inspect it closely, along with the rest of the carb, but if you can't remove a jet, you should be able to do a decent job of spraying and blowing them out with compressed air. You're trying to make sure the hole is clear in the jets. Checking/cleaning the passages is much better with the jets removed. How involved in the carb cleaning you get is up to you.
Remember to immediately rinse off any carb cleaner that contacts rubber parts.
As for your mixture screws, you can't use another model to adjust yours by, though there can be similarities. Though some people have a hard time, I suggest setting the screws using the highest rpm method. Compensation jetting never works. It just makes more problems.
If the bike still has a problem after you work on it, the problem may be effecting how the mixture screws would normally adjust.
You're POSITIVE the vacuum synch was good? You exercised the throttle several times and double checked all levels??
Anyway, try this stuff we've suggested and good luck.

[bgk]

I did some work on the bike this weekend, not exactly as I intended do, and I got some mixed results, as follows:

First, I pulled the fuel tank and air box off, and there was so much room to remove and inspect the air jets (at 7 o?clock position looking at the carbs from the air box side, and air passages at 5 o?clock ditto, as Keith described) that I chose not to pull the carbs.

I removed all four air jets and sprayed the jets and all eight passages and the slides and openings under the slides with carb cleaner, and I poked the jets and all eight air passages with steel guitar string wires and sprayed carb cleaner through them again and again. I believe I could tell everything was clear, because spray would go in one passage, and out through another. During this entire procedure, no gunk came out anywhere, no particles or dirty-colored spray, just clean spray. After I re-installed the air jets, I started up the bike in the garage with the filter box off the carbs, and she started right up and idled nice on part choke. While the bike was running, I sprayed some carb cleaner into the slides and noticed the idle bog down whenever I sprayed.

Also, while I had the filter box off, I adjusted the cam chain tensioner (while the tensioner was still mounted on the bike) following the step by step directions in the recent summary post by Sean (Shanzi). Finally, I tightened the bolts on the oil pressure sending unit, where I had a slight oil weep.

Then, I put everything back together and took the bike for a 20-minute ride on suburban roads. Probably not long enough for a good test ride to check the plugs, but the only time I had available before my son?s football game.

The good news is that my cam chain noise problem between 3000 rpm and 4000 rpm went away. The bike now sounds much smoother in this rpm range and seems slightly smoother at all other rpms. Also, the oil weep at the sending unit is gone.

The bad news is that the air jet and air passage cleaning service didn?t do a thing to lighten my plugs. The insulators on all four plugs are still variously in the range from brown to black. I?ll try to get more riding time and associated plug inspection/diagnostic time today (Sunday), but chances are slim with a full schedule of family activities.

Any other thoughts about my dark spark plug symptoms?

[KEITH KRAUSE]

In my last post I admit I said you should be able to do a decent job of cleaning the jet (itself) but taking the carbs apart is best. There's a chance you did clean the jets well or they didn't need cleaning, but you don't really know if the pilot circuit and its passages are truly clean.
So the chance the pilot curcuit is still messed up is possible.
From your past description, this does sound like a carburetion problem, not spark/compression related.
I would still adjust those mixture screws using the highest rpm method AND verify the vacuum levels. If the screws/levels are off, re-set and test.
If nothing wrong there then the carbs will have to be re-checked, including cleaning, o-ring inspection, float levels, etc.
If the bike was here, I'd just get into the carbs probably, but I'm trying to factor in your carb work abilities you mentioned and find an "easier" cure if there is one. This causes me to make a suggestion that may not be exactly what I would do first.