Oddity on 3 cylinder

[darrell3001]

Hello All,

Im finally getting around to working on an 83 GS1100ED that i acquired about 8 years ago. I have no records for this bike as it was bought at auction. Im seeing some very strange symptoms on number 3 cylinder. I thought i would post these and get feedback before i go any further.

Overall, the bike seems to have been well maintained, although, it does seem to have set outside (covered) for several years. The bike was running well when i bought it.

Background

- Carbs have been removed and professionally reworked.
- Using PODS instead of air box
- Factory exhaust system
- All hoses, including intake/carbs boots, replaced with Suzuki parts
- Fuel take thoroughly flushed. Inline fuel filter installed
- Oil changed
- Battery replaced
- Plugs gapped

I got her running last weekend, but idle was very rough. I spent some time looking at this today. Ive got idle working well now. However, ive been digging a bit deeper and uncovered a mystery re: cylinder 3.

Symptoms

1) Using a ColorTune, i noticed that i had nice blue burn on 1,2 and 4. Noticed that i have non-blue on number 3. BTH, ive never really been able to tell the difference between lean/rich based on color of ColorTune.
2) With ColorTune installed on number 3, i adjusted the mixture screw on the top of the BS34. To my surprise, this had ABSOLUTELY NO affect. Humm.. Ok, moved the ColorTune to number 2 and adjusted the mixture screw and got expected results (ie color changed from blue and idle degraded). Moved it back to number 3, and got same results. No matter how much i moved the screw, it just stayed non-blue.
3) Also, i measured the exhaust pipe temp with an infrared thermo and found that the number 3 exhaust pipe is running at least TWICE as hot as the other three at the same location of the exhaust pipe.
4) Checked compression and found all 4 measure more or less the same
5) Next, i hooked up my vacuum sync gauges and i found that number 3 seems to have low vacuum. At least that is what gauge reports. At the very least, number 3 is reading significantly lower than the other 3.
6) I decided to try and rule out a vacuum leak. Sprayed carb cleaner around number 3 carb and did not notice any reaction from engine, so i dont think i have a vacuum leak.


This is where ive left off for the day.

Im thinking that i may have an intake valve that is out of adjustment. This is what my instincts tell me. Can anyone shed any light on this? I can totally believe that the intake valve may be out of adjustment. However, the symptom that i cant seem to explain is the run-away temp on the number 3 exhaust cylinder. Why would an intake valve adjustment be causing a run-away temp on the exhaust? Anyone got any ideas or guidance?

Many thanks in advance,

Darrell

[Rich82GS750TZ]

Edit your post and add a space between your #’s and your numerals. We’ve covered this before. Ever since the upgrade, #’s followed my numerals displays goofy links. We don’t know why.

[phydeauxmutt]

I think you are about the second person to report that you saw a change in the flame color with the Color Tune and CV carbs. Most of the time, we have to settle for consistency of flame, and adjusting as lean as possible, while maintaining a steady burn. The color never changes.

What did you do? What tips can you offer on how to get the color to change?

[Brendan W]

If that inline fuel filter is for pressure pumped systems you might be starving fuel and there is always one in the litter that feels it first?
Mixture screw having no effect doesn't seem right and points a finger at that carb at least?

[darrell3001]

Edit your post and add a space between your #’s and your numerals. We’ve covered this before. Ever since the upgrade, #’s followed my numerals displays goofy links. We don’t know why.

Ok. Did that. Thanks!

[darrell3001]

If that inline fuel filter is for pressure pumped systems you might be starving fuel and there is always one in the litter that feels it first?
Mixture screw having no effect doesn't seem right and points a finger at that carb at least?

Humm. This does not feel like a carb or fuel starvation issue. It feels like a (lack of) vacuum problem. One thing i forgot to mention in my original post.. When adjusting the fuel mix screw.. If i screw it all the way down, the bike die on idle. So obviously the adjustment is having some affect. Also, when i put the gauges to do the throttle sync, the gauge on the number 3 is registering very low vacuum. My next step is going to be to pull the valve cover and check the clearance on the valves. What i hope to find is an intake valve with a very large clearance. This seems the only culprit that could be causing low vacuum. Compression test was good on cylinder 3 so this seems to tell me that vacuum would also be good as well.

Im still stumped on the runaway temp readings on the exhaust pipes. I saw a guy doing this on YouTube. In his video, all of the exhaust pipes warmed up evenly if things are setup correctly. it just seems damn odd that i would have this runaway temp on the very cylinder that is giving me strange readings.

I will keep everyone posted on my progress.

Regards,

Darrell

[rphillips]

Just a thought, if carb 3 has significantly less vacuum, it is sucking significantly less fuel thru the carb won't 3 be significantly leaner (& hotter) than the others.

[darrell3001]

Just a thought, if carb 3 has significantly less vacuum, it is sucking significantly less fuel thru the carb won't 3 be significantly leaner (& hotter) than the others.

Does "leaner" translate to "hotter?"

Logically, i would think that "leaner" would translate to "cooler." If you are suggesting that its the other way around (ie leaner = hotter), then im hopeful that i may be on the right track and could expect to see an intake valve out of adjustment once i pop the valve covers off. I would certainly be doing the happy dance if that is true!!!

Best Regards and Thanks,

Darrell

[93Bandit]

Does "leaner" translate to "hotter?"

Logically, i would think that "leaner" would translate to "cooler." If you are suggesting that its the other way around (ie leaner = hotter), then im hopeful that i may be on the right track and could expect to see an intake valve out of adjustment once i pop the valve covers off. I would certainly be doing the happy dance if that is true!!!

Best Regards and Thanks,

Darrell

A lean burn is hotter than a rich burn. An increase in oxygen (lean) creates a hotter fire.

[decker7]

I'm having the same exact issue. Do you have any update on what you were able to find/determine? I have cleaned the carbs and checked valves. Everything seems to be in good condition.

[phydeauxmutt]

Re-reading your original post, you say that cylinder 3 is "low on vacuum".
That tells me that it is open farther than the others.
You need to do a carb sync, THEN re-check your mixtures.

Also need to verify: which cylinder are you calling number 1?
Number 1 is under your clutch hand, number 4 is under your throttle hand.
Is it still number three that has low vacuum?

[darrell3001]

I'm having the same exact issue. Do you have any update on what you were able to find/determine? I have cleaned the carbs and checked valves. Everything seems to be in good condition.

Hi decker. So here is where im at with this. First, as the post above indicates, the lean condition was caused by the carbs being out of sync. The butterfly on the number 3 was just slightly ajar and the other three where completely shut. Second.. If you dont have a set of gauges, just order a cheapo set on amazon. Also, you probably want to order a hanging aux fuel tank as well. You will need to have the tank off to do the carb sync. A couple of things that i learned while doing this.

1) Get yourself a flexible screwdriver. You will need this to get to the adjustments on each of the carbs.
2) Ignore what the gauges say about "low on vacuum." The main thing is that you want all of the needles on the gauge to all be at the same position.
3) after you make an adjustment, dont forget to do a quick rev and let it settle back to an idle.
4) Adjust the inside adjustment first and get 2 and 3 synced, then do the 1 and 4. Rinse and repeat until you get them more or less the same.
5) (and MOST important).. LESS IS MORE. you will be making very tiny adjustments. When i say tiny, im talking about 1/8 of a turn MAX.

The tiny adjustment thing was key to helping me understand how to diagnose this. I was making the mistake of trying to adjust all three adjustments and then checking the gauges. It takes some time, but you can easily see the needle move when you make tiny adjustments. Once i got them synced, the red hot condition on the number 3 exhaust went away; that cylinder was just running very lean.

Now, with that said, im still not completely satisfied with the idle. The midrange and top end are fine, but the idle is still choppy and tends to stall after a while. The guy who did the rebuild put in 47.5 pilot jets. This is 2.5 above factory, but im thinking that this is still too lean. I bought a pilot jet kit of Amazon and im going to move up the chain on the pilot jets and see if i can get a better idle. The main jets seem to be fine. Im thinking that the pods may be leaning out the idle circuit too much. If i see any success, i will reply to this thread.

Hope this helps.

Best Regards!

[decker7]

Hi decker. So here is where im at with this. First, as the post above indicates, the lean condition was caused by the carbs being out of sync. The butterfly on the number 3 was just slightly ajar and the other three where completely shut. Second.. If you dont have a set of gauges, just order a cheapo set on amazon. Also, you probably want to order a hanging aux fuel tank as well. You will need to have the tank off to do the carb sync. A couple of things that i learned while doing this.

1) Get yourself a flexible screwdriver. You will need this to get to the adjustments on each of the carbs.
2) Ignore what the gauges say about "low on vacuum." The main thing is that you want all of the needles on the gauge to all be at the same position.
3) after you make an adjustment, dont forget to do a quick rev and let it settle back to an idle.
4) Adjust the inside adjustment first and get 2 and 3 synced, then do the 1 and 4. Rinse and repeat until you get them more or less the same.
5) (and MOST important).. LESS IS MORE. you will be making very tiny adjustments. When i say tiny, im talking about 1/8 of a turn MAX.

The tiny adjustment thing was key to helping me understand how to diagnose this. I was making the mistake of trying to adjust all three adjustments and then checking the gauges. It takes some time, but you can easily see the needle move when you make tiny adjustments. Once i got them synced, the red hot condition on the number 3 exhaust went away; that cylinder was just running very lean.

Now, with that said, im still not completely satisfied with the idle. The midrange and top end are fine, but the idle is still choppy and tends to stall after a while. The guy who did the rebuild put in 47.5 pilot jets. This is 2.5 above factory, but im thinking that this is still too lean. I bought a pilot jet kit of Amazon and im going to move up the chain on the pilot jets and see if i can get a better idle. The main jets seem to be fine. Im thinking that the pods may be leaning out the idle circuit too much. If i see any success, i will reply to this thread.

Hope this helps.

Best Regards!

Thank you! I am planning on doing my carb sync over the next day or so.

[gustovh]

Interesting post. This is my take, first do a lean best idle adjustment. First Start and warm up engine to idle. Start with Home and adjust the pilot screw in until the engine stumbles and then back it back out 1/8 turn, the idle may speed up and need to be readjusted. Do that to all carbs a couple times, this sets the pilot circuit to leanest healthy point. After you are satisfied with that then do the syncing. The manual shows cylinders 2&3 to be a half bubble lower than 1&4.

This should give good results with clean carbs. GL

V

[Maddevill]

Whenever dealing with a bike with an unknown maintenance history, checking valve clearance should be one of the first things to do.

Mad