Left side not firing?

[facepants]

The right side of the motor gets a lot hotter than the left.  I thought that maybe the left side wasnt firing.... so i disconnected the cable on the left side while the bike was running, and nothing happened.  It kept running the same.  Reconnected it and went to the right side... did the same thing and the bike died immediately.

Does that mean that the left isnt firing or is there something special about the right that allows it to keep the bike running on its own?

BTW, there is spark coming from both wires and I bought new plugs... didnt make a difference.

[hmmmnz]

left isnt firing.
change the coils over, if the problem changes side then your coil is stuffed, if it doesn't then its either the wiring going to the coil, or from coil to spark plug or its the carb

[Jughead]

Original Plug Caps or NGK Resistor Caps? If you Have Aftermarket NGK esistor Caps on it toss them because the Resistors Build up too much resistace over time.

[yamahonkawazuki]

Original Plug Caps or NGK Resistor Caps? If you Have Aftermarket NGK esistor Caps on it toss them because the Resistors Build up too much resistace over time.

[Cal Price]

My Yamaha sometimes sulks and does this.

Do the simple stuff first.

Clean plug, check gap, make sure plug - lead interface is clean and secure.
Lay the plug etc on the fins or engine somewhere and press the starter, if you hold the plug on make sure you have on rubber gardening gloves or somesuch. You should be able to see a spark, this will also blow any crap from the cylinder out or make obvious a problem if one exists.

Normally this fixes it, if not take the advice above, when you get it sorted expect some smoke for a while as crud tends to build up in a non-firing cylinder.

[gsJack]

Had the same problem on and off this past spring, my garage is very damp and sometimes in the spring there is more dew on the bike inside the garage than on cars outside.   

Problem turned out to be a slightly loose plug wire in the left side coil allowing spark to take path of least resistance when bike was damp.  I tightened down both plug wires into the coils and tightened the caps down on the plug ends and haven't had a problem since.  There's a screw post where the plug wire goes into the coil so it can be tightened.

Parts fiche shows a boot over that connection but there are none on my 02 GS, don't recall if the 97 had boots there and didn't bother to check.

[facepants]

Checked spark as you said... spark is fine
checked gap... correct gap
switched the cables to opposite sides, right still fires, left still doesnt
wires/caps are stock

it doesnt seem like an electrical problem...

however, i did open up the carbs and found that the left diaphraghm is torn.  would this prevent the left side from firing? 

[hmmmnz]

it wouldn't help. it would stop the right amount of fuel getting there.
fix it and try again, if still not working change the coils around. its a 2 minute job.
then you'll at least know if the coils are goosed or not

[gsJack]

Also make sure there isn't anything wrong mechanically by checking compression.  Finger in the hole should suffice to make sure valves are functioning ok.  Pull plugs and turn on key and hold finger tightly over a plug hole and crank engine.  Finger should blow away from the plug hole with a loud pop if there is adequate compression.  Repeat for other cylinder.  I tie the clutch lever to the handgrip with my hankie while doing this to complete cranking circuit and complete test using only 2 hands.   

My 02 GS also acted the same way described above starting on one cyl only when it had a stuck valve bucket.  Freed up and ran smoothly shortly after start up all summer but didn't free up when weather got cold and resulted in broken valve.  Compression check will tell if valve stuck or if zero shim gap is making a valve tight.

Carb still needs fixed too.

[Rangerkyote]

From the left field... and from personal experience:
Synch your carbs.  My left buterfly was closed just slightly more than the right, just enough that it wouldn't allow the left side to fire.  As soon as I cracked the throttle they both ran.  This is my first time around a GS so I didn't know what it was supposed to sound like at idle.  Amyway, a few turns on the screw between the throttles fixed the problem.  Try it, might work for ya.

[red_phil]

Also check the Vacum line from the left carb to the fuel tap for leaks.
If the fuel tap leaks fuel into this line the left cylinder runs horribly rich.
If the line leaks air into the left carb thenthe left cylinder runs lean.

Been there, done that.

[Egaeus]

To check for a carb balance problem, simply unplug the right and see if you can start it at all (with a bit of throttle).  If it won't run on the left at all, then it's not the balance. 

My bet is the diaphragm.  If it's the one on the top of the carb, then it's not going to pull up the slider thingy.  You get little air and little fuel, meaning that the cylinder won't run.

[Toledo Jim]

I seem to remember someone saying something about the auxiliary ground (the small wire off the negative cable at the battery) causing problems with one side not firing if it was loose or broken. (I think Srinath said it maybe?)

Jim

[The Buddha]

Yup auxillary ground. The extra black wire from negative battery post. The smaller one, poor contact = one cyl missing ... problem is, on different bikes its a different cylinder. I have lost left and right due to this problem on 2 different bikes.
Also the crank trigger could be a problem too.
Of course your vacuum line oges to the left, you have a leak there like a line with a crack in it, and bingo.
Cool.
Srinath.