#2 cylinder always rich and fouled

[danny01975]

New to me 1982 GS1100 GK. PO changed the main jets to 120. Pilots are stock 40's. Original air box. Delkevik 4 into 1 exhaust with the center baffle removed. All pilot screws are set at 3 turns out using the engine RPM as a guide. The bike starts and idles perfectly and runs really well at mid and WOT but has always had a stutter at 1/8 throttle. Also, the number 2 cylinder is always fouled out. I'll clean the plug and put it back in, and it only takes about a day to foul out again. Also, it smells like gas at idle.

I finally took the carbs apart and to check them and document what was done previously. Everything was really clean and the float heights we all right on. The number two carb bowl had some light sediment in the bowl and the pilot was partially blocked. I was able to clean it out using carb cleaner and compressed air. I did clean all of the passage ways for the main and pilots and made sure the bowls were all spotless. But I did not split the carbs or do any kind of ultrasonic cleaning.

Put it all back together and it ran like a monster. No stuttering at all. But not long after, it started hesitating again at 1/8 throttle. Took the #2 plug out and sure enough, it's black black. Also, all the other plugs are always perfect. It's just the #2 cylinder which seems to be the source of the issue.

My question is, should I just replace the pilot? Should I just dial the #2 pilot back a bit? Or is there somewhere else I should be looking?

 

[dgates1]

Bad petcock diaphragm letting fuel got down the vacuum line into carb 2 would be my guess.

 

[danny01975]

Bad petcock diaphragm letting fuel got down the vacuum line into carb 2 would be my guess.

Huh.. I hadn't considered that. How would I check that? From what I can tel the petcock doesn't seem to leak.

 

[Nessism]

Replace the normal vacuum hose with a piece of clear tubing, just for the test.

 

[rphillips]

How about remove vacuum hose, plug the nipple on the carb and the petcock with a golf tee or correct size rubber cap, then run the bike on PRI. to see if problem persists. Be careful, if you run out of gas on PRI., you won't have any reserve.

 

[danny01975]

Bad petcock diaphragm letting fuel got down the vacuum line into carb 2 would be my guess.

I pulled the vacuum line so I can go match it up with some clear line of the same size and I did notice it was wet on both ends and it does smell like gas.

should there be any gas at all in there? My guess is probably not.

 

[tom203]

should there be any gas at all in there? My guess is probably not.

good guess!

 

[dgates1]

Nope. That tube should be dry. From what everyone says on here, it's not worth it to try and rebuild the petcock with a kit. Look for a replacement.

 

[Rich82GS750TZ]

New, OEM style, model specific petcocks can be had at georgefixs.com
https://www.georgefixs.com/brand-ne...s550-gs650-gs750-gs850-gs1000-gs1100-petcock/
Haven't had to replace mine yet but will get one of these when I do. Have only read good things.
As with everything, verify fit with your particular bike, especially mounting bolt hole spacing. Link above says it will fit:
82-84 GS 1100 GKZ/GK2/GKD/GKE GS1100GKZ GS1100GK2 GS1100GKD GS1100GKE,​
among others.
Mounting holes are 44mm center to center.

 

[danny01975]

Nope. That tube should be dry. From what everyone says on here, it's not worth it to try and rebuild the petcock with a kit. Look for a replacement.

So I already have a petcock rebuild kit that I can't return that I ordered some time ago. I may just give it a go. If that doesn't work, then I'll just replace the whole thing.

 

[Cipher]

So I already have a petcock rebuild kit that I can't return that I ordered some time ago. I may just give it a go. If that doesn't work, then I'll just replace the whole thing.

A conical felt Bob on a rotary tool cleans up the mating surface of the cock bit.
the plastic bit my be grooved

 

[danny01975]

Replace the normal vacuum hose with a piece of clear tubing, just for the test.

Winner winner chicken dinner!!
https://imgur.com/a/986KUyU

 

[gustovh]

A conical felt Bob on a rotary tool cleans up the mating surface of the cock bit.
the plastic bit my be grooved

yes and a bit of brasso to clean up the mating surface to the “O” ring, which is probably your problem.

V

 

[KiwiAlfa156]

Winner winner chicken dinner!!
https://imgur.com/a/986KUyU

Well the only way gas gets into vacuum tube is past the diaphragm. So its likely torn or holed.

 

[danny01975]

Well, the rebuild kit did nothing. It's still sucking fuel past the diaphragm. Albeit, less fuel but I can still see activity in the clear tube. And now it leaks as well. :/. Probably from me over tightening it after realizing it still wasn't working.

Looks like I'll be ordering a whole new petcock. Will update once that's here and installed.

 

[Rijko]

I have seen several rebuild kits that have an o-ring on the diaphragm that's a little bit smaller than the original.
And the diaphragm rod almost half a millimeter shorter than original.
So the o-ring never seats nicely, and gas flow does not shut off completely.
An o-ring slightly larger solved that for me.

But a buddy recently solved that by placing 2 small rings in the recess behind the spring, and it held up to now.
( stretching the spring was not sufficient )
Might be worth a try ?

 

[Bammer07]

Newbie question. I too have a rich fouled cylinder #2 plug (as well as some other issues). Replacement petcocks obviously must be vacuum style, but are there other criteria they need to meet in order to be compatible?

 

[Rich82GS750TZ]

Hi Bammer07, welcome. It would be appreciated if you’d make an introductory post in the GS Owners forum.

To answer your questions:
Nothing obvious about the petcocks. Some folks replace original vacuum types with a simple but expensive fuel tap made by Pingel. They are typically simple On/Off design, probably requiring an adaptor plate that match the threaded hole spacing on the bottom of your particular tank. Because they are simple ON/OFF, you must remember to turn it On before you start the bike. More importantly, you ABSOLUTELY MUST remember to turn it OFF after you park the bike. Failure to do so will more than likely result in an empty fuel tank, and engine full of gas mixed with the oil, and a huge mess. Also, if you use this type of non-vacuum petcock, you must plug the vacuum port on the carb body. (Front of # 2 on CVs, or back of # 3 for VMs).

The replacement OEM-style petcocks at georgefixs that I linked above are year/model specific.
And I think but am not positive, that they only sell for GS models ‘80 and newer. Different years and models have varying threaded hole spacing to line up with the holes on the bottom of your particular year/model tank. Be certain of the year/model and hole spacing before you buy any petcock.