82 Suzuki GS1100G - Carb problem

[williamcryan]

This is so frustrating. I just spent over an hour posting a detailed description of my problem and plan to fix the problem and when I hit submit, I got a message that I was logged off and all my work was not recoverable.

Here we go again. I will save to a clipboard occasionally to avoid losing my posting.

BACKGROUND

1. I have an 82 Suzuki GS1100G with Mikuni BS34SS carbs, 4 into 1 Vance Hines exhaust.
2. The top end was rebuilt two years ago. Valve job and new rings and carb manifold boots. The bike ran great. I replaced the coil set with a new stock Suzuki coil set and the bike ran even better.
3. Last year I used it very little but I would occasionally get a sooty fouled plug on #2 cyl.
4. This year, the #2 plug began fouling more frequently, every 50 miles or so. Not a fun ride.
5. I took the bike to my mechanic and he adjusted valves and balanced the carbs. The valve adjustment on #2 was way off he said and adjusted with right sized shim.
6. I still get the plug fouling on #2 so I decided to bite the bullet and pull the carbs and check float levels.

CARB WORK

1. I pulled the carbs and disassembled them. They looked pretty clean inside so I did not dip them.
2. I went through each component and they all looked good and I did clean with carb cleaner and used a fine wire to go through all small holes.
3. I replaced all o-rings and gaskets.
4. I changed the fuel needle valve from #2 to #3, since #2 was my problem and there was no apparent difference, but just to see if there was, the problem on #2 would show on #3.
5. I checked the float levels, but they all seemed to be the same height of .81, but I'm not sure I measured them accurately, but I did get consistent measurements.
6. I reasembled and bought a Carbtune to balance the carbs. A GS Resource member helped me balance the carbs and set the air screw to 2 turns out.

ROAD TEST

1. Horrible fuel consumption. I took a 200 mile ride and I could almost see the fuel level going down. No fuel leaks. I got about 20 mpg. Previously I got about 32 mpg and my buddy with a similar motorcycle gets about 35 mpg.
2. Performance is a little rough also.
3. Back home. I just checked the plugs and #1, #3 and #4 look tan and burning ok.
4. #2 plug is not sooty fuel fouled. It looks wet and shiny as though it is not firing. hmmm.

NEXT
Having learned a lot from pulling the carb and all that I want to get it right this time.

1. I'm first checking the ignition on #2 and #3 by switching the plug wires to see if I'm getting good firing on both cylinders.
2. Pulling the carbs and checking the float levels.
3. I will submerge the floats to check that I do not have a leak.
4. I'm going to change the float height from the .81 which is below the manual spec of from .84 to .92. I will set the height to .84
5. One thing I missed that I saw in the manual was applying Blue Loctite to the set screws for the choke link and to all the scews for the two carb plates holding the carbs together. I don't want the screws to come loose and fall off in the future from vibration.
6. Reassemble and reinstall the carbs and rebalance.
7. The air screw is set to two turns out.

A QUESTION

1. I see references to the Pilot screw being set and I think there seems to be confusion between the Pilot screw and the Air screw. The Pilot screw has the rubber cap and I saw no references of setting this. I scewed the Pilot screw to a firm set and did not back it out. The air screw is backed out two turns.

ANY COMMENTS, TIPS, SUGGESTIONS WOULD BE APPRECIATED

Bill

[Nessism]

A sooty #2 plug could mean the petcock is dumping fuel down the vacume port fitting and into the #2 carb. You might want to replace your vacuum line hose with some clear tubing to see if anything funny is going on.

Another thing to try is building yourself a fuel level gauge like the Suzuki service manual shows; using a tool like this will allow you to measure fuel level, not just trust the level is what you expect based on measuring float height.

Good luck and hope this helps.

[williamcryan]

Thanks Ed

Hmmm, Several times when removing the vacuum hose, I noticed a wetness but didn't know quite what to make of it.

I will check out how to build a fuel level guage.

Bill

[Steve]

I see references to the Pilot screw being set and I think there seems to be confusion between the Pilot screw and the Air screw. The Pilot screw has the rubber cap and I saw no references of setting this. I scewed the Pilot screw to a firm set and did not back it out. The air screw is backed out two turns.
ANY COMMENTS, TIPS, SUGGESTIONS WOULD BE APPRECIATED

My suggestion would be to eliminate some of your own confusion.

What you are calling a "pilot screw" is actually the "pilot fuel JET". Yes, it lives under a rubber cap, but it should be installed snugly, there is NO adjustment possible without replacing it with a jet of a different size. There is a "pilot AIR jet" in the intake throat of the carb. Together, they set the A/F ratio for the "pilot fuel mixture". There are three small holes at the top of the outlet of the carb where this mixture is able to flow. Two of them are just behind the throttle plate, and only flow as the throttle is progressively opened, the third one is under the "idle mixture adjustment screw", which is what you are incorrectly calling the "air screw".

On the VM-series carbs, you do have fuel screws and air screws. On your BS-series carbs, the ratio is set by jets, you can only adjust how much of that mixture gets to the engine. Two turns will probably be the minimum for decent running on a stock engine, might do better with 2.5 or 3 turns.

.

[SqDancerLynn1]

Block off the vacuum hose on #2 and run the bike on prime. Then recheck the #2 plug

[bwringer]

Jeez, buy a new petcock already!

You've already seen gas in the vacuum line, you're getting all the textbook signs of a bad petcock, it's bad, replace it, ride happy for the next 20 years. It happens to every GS.

No, the rebuild kits aren't worth the trouble and time. No, you can't fix it using bubble gum, spit, twine, and JB Weld. You need a new one. It's a critical valve controlling an explosive liquid six inches from your crotch. Don't fart around.

[williamcryan]

Thanks guys

bwringer, I appreciate your sense of humor and I think you have isolated it to the petcock. allright allready, I'll get a new petcock.


Steve
thanks for the clarification and confirmation of what I believed to be correct.

SwdancerLynn1

Good idea, I'm just going to get a new petcock as bwringer has suggested.

Bill

[williamcryan]

Gas in vacuum hose

An update. I changed the vacuum hose to a clear one and plugged the vacuum hose from the petcock. I started the bike with fuel lever set to on and set to prime. The vacuum hose is filled with gas, so I believe that accounts for my rough ride and high fuel consumption.

I haven't run the bike on the road yet to check the plugs, but at idle and with some throttle, I'm getting some smoke.

I'm waiting for my bid for a new petcock to be accepted and getting it within a week.

QUESTION

Should I go ahead an pull the carbs and check my floats levels now and be ready for the new petcock and then balance the carbs or just wait and see if the petcock solves my problem. Making a float level gauge has been suggested, but I don't know how to make one and set it up. Does anyone have specs on how to make one?

Bill

[slip]

Jeez, buy a new petcock already!

You've already seen gas in the vacuum line, you're getting all the textbook signs of a bad petcock, it's bad, replace it, ride happy for the next 20 years. It happens to every GS.

No, the rebuild kits aren't worth the trouble and time. No, you can't fix it using bubble gum, spit, twine, and JB Weld. You need a new one. It's a critical valve controlling an explosive liquid six inches from your crotch. Don't fart around.

[williamcryan]

Bike is running so sweet

Update -

1. Battery ran out of juice and it was replaced.
2. Did a helicoil on #2 plug because of cross threading and plug not seating all the way.
3. Replaced petcock with a new one.
4. Balanced the carbs.

It is running so good and is such a pleasure to ride. It is fast,, runs up to 70 in second at 8k rpm quickly. Feels like I could do a wheelie if it didn't scare the crap out of me to do one.

Bike has 92k on it, I think motor has 67k.

I am so pleased. Thanks guys for your tech help.

Bill

[argonsagas]

The G will do wheelies, but not very high and not for an extended time, unless you have quite a bit of weight towards the rear.

If you rev it high and pop the clutch it will sit up higher, but that is NOT recommended because it tends to be VERY hard on the final drive splines.


That said, in first gear and with a good twist on the throttle from GO! an 1100G will easily clear an intersection on its rear wheel and set back down smoothly.

[bwringer]

*sniff* I just love a happy ending!