Cylinder 2 not firing

[PB_Maine]

I have an 81 GS1000L with 20K mi on it.

Cyl #2 is not firing, the pipe is cool and removing the plug wire does not affect how the engine runs. The spark plug is firing about as hot as the other ones, but is fouled, and wet, shortly after it is cleaned.
Compression is about the same as the other cylinders. I removed he carbs and they look fairly clean, however I didn't dissassemble them and I fear doing so because while I'm fairly mechanically inclined I've had little success fixing carbs. Just for the heck of it I'm going to do as the manual suggests and swap the coils and see if the problem moves. I know, I've got spark but if that doesn't work I'll have to deal with the carburators. I did use a lot of stabilizer before storage this year and have run a few tankfulls out since. This didn't take long because of the lousy milage I'm getting.
Does anybody have any suggestions that may help? Ones that don't include carburator disassembly are especially welcome.

Thanks

[Redman]

Does 1000L have a vacuum operated petcock?

If so, one possibility might be a problem with vacuum operated petcock. It takes its vacuum from #2 carb, so there is a tube from carb throat to the vacuum operted petcock. Various Probelms with petcock can then cause problems with cylinder #2, either a big vacuum leak or maybe sucking extra gas.
To eliminate this as a test, can either pinch off the tube between the carb and petcock, or pull it off of petcock and plug it. Will then need to put petcock on PRIme.

[Steve]

Another thing to try before you go to the effort of switching the coils...
just swap the plug wires between #2 and #3. They come off the same coil and fire at the same time, so that will tell you if it might be a bad plug wire (if the problem moves) or a bad plug (if the problem does not move).

Just trying the easy stuff first.


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[bwringer]

What do the plugs look like?

If #2 is fouled, you have a bad petcock. Replace the petcock -- don't try to rebuild it. That way lies only madness...

[PB_Maine]

I'll try it

I just talked with a fried of mine who is also a GS fanatic. He also suggested the petcock. I replaced the hose because I thought it was a vacuum leak but I didn't think of the petcock allowing it to suck gas. I'll try it tomorow and get back to yas. If that doesn't work I'll try the plug wire swap.

Thanks for the help..

[chef1366]

Check and see if there is gas in the petcock vacuum line.

[svahnm]

I must tell my story too.

I have gs850g '79.

It had weird spark failure in cylinder #2. Swapping parts (coils, wires, plugs) did NOT move the failure. Compression was equal. Carburetors were working quite fine.
Spark seemed to be ok also in #2, while plug was taken out and grounded cylinder head. However inside cylinder with compression it must have failed.

The engine was running fine with 1&4&3 cylinders, but 2 wasn't.
If I removed 1&4 sparkplug wires then #2 started to run happily with #3, so there was lack of energy. Somehow #2 was giving up first.

I had changed all the ignition components (it was upgraded electronic aftermarket ignition).

Finally mystery solved with new battery, or at least it started to work with that. Old battery was ok too and that is why I didn't change it before.

So if you don't find anything wrong with petcock, at least try to run engine with only 2&3 cylinders 1&4 wires removed (and 1&4 wires grounded with two extra plugs to head). If #2 starts to work then it has something to do with strenght of ignition.

Edit:
Oh, and don't ever assume you have working spark plugs if they are rather new, they can die anytime....

[PB_Maine]

It was indeed the petcock

I removed the vac hose from the petcock and plugged it with a pencil. When I moved the valve to prime the gas ran out of the pipe. So as you can imagine it made # 2 run rich. It is now running on all 4.

Before I read your responces I did open the carbs and give them a light clreaning. Just as well because there was a bit of crud in the bowl and above the rubber plug that covers the idle jets. One question though, what do the needle valves do that are above the throat where the carb goes into the head. I took them out and cleaned them and put them about where they were. My manual makes no reference to the sdjustment. Are these the air mixture valves that are, according to the book, illegal to adjust. If so I'm back to biking for 2 years and already an outlaw.

Anyway, Thanks for the advice and saving me from a long drawn out process.

[Steve]

Yes, those are the ones that are illegal to adjust. :shock:

Just sit tight, the EPA police will be there in just a few minutes. 8-[










While you are waiting for them, snug up the screws to see how many turns it takes to lightly seat them, then write it down. A good place to start, if they are very far off, is about 2 turns out. Warm the bike up thoroughly (darn, another excuse for a ride), then slowly turn each of those screws, listening for the highest rpm. Start with about an 1100 rpm idle, tweak a screw. Adjust idle back to 1100, tweak the next screw, etc. When you are done, record the new settings and save it somewhere that you can find it next time.


The EPA police are just about there now, but you will be able to outrun them now. \\/


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[headsbikesmopars]

Take a compression test of all the cylinders. Be sure to open the throttle. Too much fuel like that will/can wash down any oil on cylinder walls.. this can scuff the rings and walls real fast..ask me how I know. I had 171-175 lbs. on 1, 3 and 4. 125lbs on number two, took just about 20 miles to do this too. On newly rebuilt engine. Had to 're-ring' number 2 and all is well. In the future..ANYTIME I loose number 2..I shut it down and check petcock first. FYI, Terry.

[PB_Maine]

I'm worried about that

I put about 20 miles on it before I figured it out. I don't think I'll do the compression check and go with a false sense of security, at least until I find out if I'm going to jail for adjusting the idle scews.

[Skyboy8950]

I have the same problem with my GS650GL. The guy I bought it from said the petcock was working, so he introduced his own shutoff right next to it to shut off the fuel. I guess he didn't know (as well as I) that the petcock serves another purpose. I pulled the vacuum from the carbs, started 'er up, and plugged the hole with my finger. Nothing happened until I let go of it. VROOM! It fired for a few seconds, then puttered out (the cyl that is). So tomorrow, I am off to find a petcock. Are they easy to rebuild?? I've seen many kits.

[steely]

Do not get the rebuild kit. They are crap. Just spend the $60 for a new one from Suzuki and forget it for the next 25 years. I have tried it both ways.