Carbon fouling problem

[earlfor]

OK Jethro, I knew the coils couldnt run the engine on 8mv, I was going to let that go for now though. hehehe So you have about 12.7 in the battery and are getting 11.3 at the coils. (dropping 1.4v) As Bad Billy said, its usually a cumulative thing.) I expect youre dropping a few tenths at each point in the circuit. Basically, youre just looking at a clean up of connections exercise. Thats a far cry from the 4.5 volt drop originally suspected.
Some electrical contact cleaner sprayed into the key ignition tumbler may help a couple tenths volt.

The good news is you installed a new battery that you really did need. The old battery only holding 12.3 was certainly on its last legs.

Earl

You mean the bar switch? I checked, I lose about 1.2 volts there, both before the switch and after the switch.

Tonight I checked my coil voltage again, this time CORRRECTLY. I had disconnected the wires to the bar switch and that is why my readings showed 8 millivolts. #-o I have 11.3 volts at the coils. I checked the voltage while the bike was running and at idle- about 13.6 volts.

I don't seem to be losing a huge amount of voltage anywhere, but I still have the slight stutter on take off (only after I sit and idle a minute). Still, I went for a nice 45 minute ride today- man I love those stock pipes. The quieter the better.

I'm gonna go downstairs and smoke one up and change out the pilot jets to my #40's. I also have a whole other set of carbs in the carb dip to swap out with the ones on the bike now. What the hell else does a loser like me have to do on a Friday night! :-D

 

[Jethro]

I was going to let that go for now though.

I figured that! I was letting it go as well, because I knew you were right about it (and that I was a meathead :lol: :lol

Anyway, I changed to the #140 pilots, down from 145 and the highest idle was found at 1/4 turn out on the mix screws (as usual). It seems better, but maybe it's all in my head beacause I cleaned her up tonight and put a badly needed new tire on the front. I also don't know if it's the jets or all the cleaning and fiddling of the electrical system. It's good that the new battery is resting from overnight at 12.7, I know that.

I'll keep cleaning up the electrical system, and spray the tumbler. But is it terrible that I lose 1.4 volts at the coils? Is this enough to cause the stumble?

Back downstairs to put the second set of 100% clean carbs together, bench synch them and pull the saddle, tank, airbox and headlight off. I'm gonna need more beer...

 

[earlfor]

I wouldnt say its terrible and would guess that the majority of GS's out there are dropping an average of 1 to 1 1/2 volts in their systems. My personal limit is .5v and I try to keep it .25v or less. The less lost voltage you have, the better everything works and the less strain there is on the charging system and battery, so clean up is a good thing.

Is it enough to cause the stumble? I doubt it. You said you found the highest idle with the mixture screws 1/4 turn out. I know everyone says to set the mixture screws for the highest idle. I dont do that. I find the highest idle and then richen them up about 1/8th turn. You might try that to see if it helps.

Earl

I'll keep cleaning up the electrical system, and spray the tumbler. But is it terrible that I lose 1.4 volts at the coils? Is this enough to cause the stumble?

Back downstairs to put the second set of 100% clean carbs together, bench synch them and pull the saddle, tank, airbox and headlight off. I'm gonna need more beer...

 

[flyingace]

Has the plug fouling gone away?

 

[KarlLMT]

Be sure to check the ground cable. I had a simular fouling problem - everything checked out fine. Someone recomended adding a second ground cable from the battery to the block. It fixed my problem!

 

[GS550joe]

Hmmm.. 1.4 volts??? sounds like it may a couple of extra diodes going to the coils... a diode drops .7 volts approximately and 2 in series would drop 1.4v thereabouts... anyone with a wiring diagram see any diodes set up in the leads to the coils.. if there are they would be there to keep any back feed current from feeding the wrong way.

 

[KEITH KRAUSE]

You shouldn't need to install smaller pilot jets if the motor is stock.
I didn't read all the replies here but you're saying the bike runs fine except at idle it slowly drops rpm until it stalls. As the motor warms up this gets worse. Plugs are sooty ONLY after an idle read. You've checked the electrical as well as you can.
Fuel starvation shouldn't be the problem because this wouldn't soot the plugs.
Too much fuel could do this of course. So could too little air.
Too much fuel: After what you've said has been done/checked to fix it, could the pilot jets be wrong or modified? Unless you know the history of the carbs, I've seen PO's install longer length pilot jets. Not all carbs have different lengths but some do. So are you sure these match up to known stock pilot jets? Same number of holes too? ANY differences? Also, any chance these jets were modified/drilled out by a PO?
Too little air: are the pilot air jets clean? What size are they? Stock?
I assume your throttle cable slack is what the factory calls for? Cable operation is smooth?
Your 1/4 turn out on the mixture screws shows something's wrong.
Just wondering, you said you have the bike set to idle at 1,300 rpm. After a few minutes, as it warms, it stalls. OK. What happens if you deliberately set the idle to 1,500 and let it idle? I don't suggest a higher idle setting, even if it helped. I just wonder what the bike would do. 1,300 rpm seems a little high already.
By the way, some factory manuals will list a higher idle as a possible contributor to plug fouling. What does your manual recommend?

 

[Jethro]

Be sure to check the ground cable. I had a simular fouling problem - everything checked out fine. Someone recomended adding a second ground cable from the battery to the block. It fixed my problem!

I have another ground in to the frame as well. I made sure they were connecting well.

Kieth, I'm glad you are here to help me once again!

The bike actually runs awesome, it will idle at 800 RPM all day long. Just a small stutter or fumble when the bike sits at idle for a minute or so. I rode about 80 miles today, love those stock pipes! (thanks Adam!)

I have completely rebuilt my carbs to exact factory specs- the manual I have been using is a Haynes, but I have my 81 factory manual for cross reference. The doner carbs were an identical 83 1100ED set that was pretty clean that had never been cracked open. I made them better than pretty clean with a dip, and re-assmebled with new o-rings.

The pilot jets were the stock #45's the other day, yesterday I put my #40's in and it seemed to help a little. Mix screws show highest idle at 1/4 turn out from seated. The pipes are stock, airbox, filter all stock. Should I try an even leaner pilot? Seems strange...

Just wondering, you said you have the bike set to idle at 1,300 rpm. After a few minutes, as it warms, it stalls.

The bike dosen't stall any more, I think that problem was a dead battery that Earl helped me determine. Problem one with the stock transformation has been fixed.

Just wondering, you said you have the bike set to idle at 1,300 rpm. After a few minutes, as it warms, it stalls. OK. What happens if you deliberately set the idle to 1,500 and let it idle? I don't suggest a higher idle setting, even if it helped. I just wonder what the bike would do. 1,300 rpm seems a little high already.
By the way, some factory manuals will list a higher idle as a possible contributor to plug fouling. What does your manual recommend?

I set the idle today to 1100 exactly, and it had no problem all day. The battery and melted r/r harness made that go away. But I still have this fumble off the line! Maybe I am being to critical, and expecting more for a 23 year old bike! If I blip the throttle I can pull away smoothly, if I don't, I chug slightly until 3500 rpm. It doesn't look very pro!8-[

 

[Jethro]

One more thing. I forgot if plug readings are pretty much worthless at idle, are they?

 

[KEITH KRAUSE]

One more thing. I forgot if plug readings are pretty much worthless at idle, are they?

Well, they can fluctuate some, that's for sure. Still, a correctly jetted/synched bike will give acceptable reads at idle. Any street motor will. You said the plugs were sooty after idling? I guess I'm a little late in replying and you've made progress.
So now the only problem is a stumble off idle/trying to pull away?
No sooty plugs?
The carbs you're using are from an '83? Your bike is an '81? If anything, we all know the factory would only go leaner from '81 to '83. So there could be other jetting differences you may not be aware of.
If you still want to try a leaner pilot jet it must be because you DO STILL have sooty plugs? Just trying to catch up with you to try to figure out the problem.
Normally, you wouldn't want to go leaner than stock jetting (pilot jet) because it would be compensating for something else wrong. But there COULD be differences between the two model years carbs/motors that require this mod' and it could work. It's very hard to tell differences sometimes between carbs. Why does a '78 750, with seemingly identical carbs, use a 102.5 main jet and a '78 1000 use a 95 main? Motors can, and do, have minor changes from year to year that require jetting changes to help with minor problems. So it would be no surprise to find that a smaller pilot jet,used in a later model carb, might fix your stumble.
Anyway, because I may still be behind your progress, why are you thinking about the smaller pilots and what makes you believe the stumble is a richness problem vs a lean problem?
Also, without being able to ride the bike, we have to rely on your word description about the stumble and what it's really like. It may be that you ARE expecting too much, maybe not, I don't know. I read all the time about how a new '06 model will have an annoying quirk of some kind, even with fuel injection.
Let us know how you've determined it's a rich problem and what you may have done to prove that. Any obvious symptoms? Gets worse as it warms up? Blipping the throttle in neutral makes the rpm's momentarily dip below normal idle?

 

[Jethro]

The carbs you're using are from an '83? Your bike is an '81?

No, it's all 83 1100ED stock, carbs, pipe, airbox and all. I still have sooty plugs when I read them at idle.

Anyway, because I may still be behind your progress, why are you thinking about the smaller pilots and what makes you believe the stumble is a richness problem vs a lean problem?

Becasue in both the shop manual and the Haynes book troubleshooting section they say carbon deposits are a result of improper fuel mixture, rich condition. And the fact that my mix screws are best set at 1/4 turn from seated, I am guessing I am too rich.

Also, last year I had pretty much the same problem with my 4-1 pipe and pod filters, DJ kit. The main indicator as to why it was rich was the intense smell of fuel out the exhaust. That has gotten much better, but I still smell some fuel.

 

[Jethro]

Hey Kieth, something I just thought about. I never re-installed the float bowl vent tubes. Could this be a factor? How long are those hoses? I certainly don't have them anymore.

 

[KEITH KRAUSE]

Hey Kieth, something I just thought about. I never re-installed the float bowl vent tubes. Could this be a factor? How long are those hoses? I certainly don't have them anymore.

With a totally stock intake, the float bowl vent lines should go back on.
Just as removing them aids the jets in drawing fuel when you run pods (desired), it would also make it too easy for the jets to draw fuel with a stock (more restrictive) intake. There would be a richening effect. How much, I can't say.
I believe the correct length is about 18". Should be 3/16" but possible 1/4"? Ask someone here with a similar model to be positive about length and ID. Since you're installing new ones, might as well do it right.They should be routed under the seat someplace. No kinks.
I've never actually ran any stock bike without the factory venting, so I don't know if this would effect only the pilot circuit mixture. Hope it works for you. Let us know.

 

[earlfor]

On my 1100/1197, I'm not running with carb vent lines installed, but I am running with no air box lid. It runs sooty with the lid on. I'm running 125 mains though.

Earl

 

[KEITH KRAUSE]

On my 1100/1197, I'm not running with carb vent lines installed, but I am running with no air box lid. It runs sooty with the lid on. I'm running 125 mains though.

Earl

No air box lid effects the intake enough that the vent lines should be removed, just as with pods.

 

[earlfor]

Yep, works just fine. The point I was trying to make is that if youre a bit rich, you can restrict fuel, or increase air. The result will be the same.

E.

No air box lid effects the intake enough that the vent lines should be removed, just as with pods.

 

[KEITH KRAUSE]

Yep, works just fine. The point I was trying to make is that if youre a bit rich, you can restrict fuel, or increase air. The result will be the same.

E.

Okie-dokie Earl.
Jethro says his problem is only at idle though. Apparently the other throttle positions burn well. If he DID want to remove his lid, he'd have to re-jet for the other jetting circuits, which he wants to avoid. He just wants stock everything.

 

[Jethro]

Okie-dokie Earl.
Jethro says his problem is only at idle though. Apparently the other throttle positions burn well. If he DID want to remove his lid, he'd have to re-jet for the other jetting circuits, which he wants to avoid. He just wants stock everything.

That's right, just as god (Ichiro Suzuki) intended it!

My bike idles like a champ, will idle at 1050 RPM all day long. But a little stutter as I leave the stop lights (unless I blip the throttle first).

 

[KEITH KRAUSE]

So Jethro, did you install the vent lines? Any change to the stutter?
Also, I forget if I asked...does the stutter get worse as the bike warms up? If you let it idle a moment, then blip the throttle (completely warmed up), do the rpm's jump up then DIP down below the normal idle? Both are richness symptoms.

 

[Carter Turk]

What about the emulsion tubes ovaling out, allowing more fuel past the needle.

I bought a set of 90 GSXR 11 carbs for my 1150 5 years ago with a used probably tinkered with Dynojet kit and used K & N's.

The needles looked really blunt on the end more so than stock.

So, I bought a Factory jet kit with needles that had a taper not a blunt end. I thought I would get more precise metering for fuel/air.

I popped those in to reccommended settings and fouled more than a dozen plugs. I leaned the pilots, lowered the needle, lowered the main, turned the airfuel mixture screws in, leaned the floats, replaced the needle jets, nothing would keep the plugs from fouling. I bought new filters, thinking that might be it. No!

I realize these carbs weren't designed for this bike, but heard other people had success with this set up.

I went back to the Dynojet kit it came with it ran finally. My unscientific explanation is the fattest part of the needle is a different diameter.

I also remembering hearing the GSXR carbs emulsion tubes had a tendency to oval over time causing a rich condition.

Thought this might be something to check. Wouldn't the needle be fully down at or near idle? If there was a wear problem there on the tubes, likely fuel would be getting by?