#2 Not Firing

[sebring38]

Cyl 1,3 and 4 are firing great, and the bike runs amazingly well on 3 cylindars.
On the #2 there is spark at the plug, but that cylindar does not fire until it gets fully warmed, and I run it at high speeds. At idle and when cold it doesnt fire at all, or very intermittently.
I have swapped plug wires around with same result. I pulled #2 plug. It is black and wet with gasoline.
Suggestions appreciated.

[83GS1100E_Tornado]

Carb problem, probably a stuck float. I would drain the float bowl for just that cylinder, bop it was a screwdriver a couple of times, and fill it back up with gas again. You might get lucky, if not, a carb rebuild may be in order!!!!

[bwringer]

You have the classic and unmistakeable signs of a bad petcock.

The vacuum line from the petcock goes to a fitting on the #2 carb. When there's a leak in the thin, delicate, aged diaphragm in the petcock, it dumps gas into the #2 cylinder, causing the plug to foul and stop running.

Replace the petcock and forget about this problem for another 20 years.

Rebuild kits are pretty iffy -- I wouldn't waste the money and time. Depending on your model, a new petcock from Suzuki is only $40 - $60.

A good source for Suzuki parts, and the best prices I've seen:

http://www.flatoutmotorcycles.com

[KEITH KRAUSE]

Yup. A bad petcock could explain it. You can prove it if you want.
Remove the vacuum line at the petcock and positively plug the line and (for safety) cap the petcock vacuum port. Remove the fouled plug and replace it or clean it very well if you can't easily get a new one. If using the old cleaned one, I'd swap it with plug #1 to help it fire better initially. Then turn the petcock to prime. Test.
Put some miles on it so any improvement isn't just because you cleaned the plug. If the plug looks good now, then it appears to be the petcock.
You may want to change your oil too if this is the case.

[headsbikesmopars]

Yes classic bad petcock. Be careful, when you even suspect this...STOP running the engine until you know for sure. A super rich mix like that will wash down any and all oil on cylinder wall. And scuff the rings. Won't take but a few (20) miles to do that too. Take a compression test after the fix is made. Be surprissed what you might find. Terry.

[sebring38]

Thanks, I am going to bet you are right. I noticed recently that my oil level went UP. Bet there is gas getting down into crankcase.
thanks

[sebring38]

Thanks All. You called it exactly right. I bypassed vacuum on petcock and it fired up and ran great. Got a new petcock on order from Flatout.
thanks,
KC

Yes classic bad petcock. Be careful, when you even suspect this...STOP running the engine until you know for sure. A super rich mix like that will wash down any and all oil on cylinder wall. And scuff the rings. Won't take but a few (20) miles to do that too. Take a compression test after the fix is made. Be surprissed what you might find. Terry.

[Rocketman]

I'm a believer. Ordered my new petcock from FlatOut this morning ($41.04 yeah!), with new o-ring, plus new fuel and vacuum lines. Once its installed, I'm hoping Ill be firing on all 4 cylinders consistently. We'll see soon.

[bwringer]

I'm a believer. Ordered my new petcock from FlatOut this morning ($41.04 yeah!), with new o-ring, plus new fuel and vacuum lines. Once its installed, I'm hoping Ill be firing on all 4 cylinders consistently. We'll see soon.

What did Flat Out charge you for shipping? Some folks have complained that their shipping for smaller orders seemed a bit higher than expected. Their service and prices have been stellar, though. Just by way of perspective, BikeBandit charges $4 to $6 shipping for smallish packages.

I need a few odds and ends, but I'm might see if they'll let me come and pick up my goodies instead of shipping them to me -- they're located about 15 minutes from my office.

[Roy]

only if parked on side stand

You have the classic and unmistakeable signs of a bad petcock.

The vacuum line from the petcock goes to a fitting on the #2 carb. When there's a leak in the thin, delicate, aged diaphragm in the petcock, it dumps gas into the #2 cylinder, causing the plug to foul and stop running.

Replace the petcock and forget about this problem for another 20 years.

Rebuild kits are pretty iffy -- I wouldn't waste the money and time. Depending on your model, a new petcock from Suzuki is only $40 - $60.

A good source for Suzuki parts, and the best prices I've seen:
http://www.flatoutmotorcycles.com

Hey guys my 1982 gs 850 gz is doing the same thing . If i park on the side stand for a while. When I start her she runs on 1 3 & 4 for about 10 to 15 secs but after that she is fine. If I park on the centre stand I have no problems at all. . Could this be a fuel tap problem & if so why only on the side stand.???

[KEITH KRAUSE]

Hey guys my 1982 gs 850 gz is doing the same thing . If i park on the side stand for a while. When I start her she runs on 1 3 & 4 for about 10 to 15 secs but after that she is fine. If I park on the centre stand I have no problems at all. . Could this be a fuel tap problem & if so why only on the side stand.???

To see for yourself how angle can effect fuel flow even though there's vacuum present, do a little test.
Dip a piece of fuel line into a gas can so there will be several inches of fuel inside the line. Press your thumb over the top. Lift the fuel line out but keep it reasonably straight up and down. The fuel should stay inside.
But now if you take the top of the fuel line and start bringing it down to create an angle just as it's mounted on the petcock on your bike, you'll see the vacuum weaken and the fuel will flow. So angle changes things.
Even if your petcock is sealing well when the bike is turned off, the amount in the line can still flow into the carb bowl and so cause a high fuel level that can be enough to cause your problem. Carbs 1 and 2 are the ones effected by this because they are on the left side of the fuel "T" and gravity will do the rest. I'm not sure why but carb 2 seems more common to have this problem.
But the reason the fuel enters the bowl is because the float needle valve isn't sealing well.
I've seen many bikes leak while on the side stand but apparently not leak, or not nearly as much, while on the centerstand. I've also seen bikes with brand new petcocks and even non vacuum Pingel valves leak while on the side stand. With a clear fuel line attached I've seen the fuel slowly drain down while on the sidestand but very little or not at all while on the centerstand. The valves looked good in many cases. Only thing that would allow this flow is a float valve not sealing well or something wrong with the float assembly operation. Many of the float valves appeared to be in good condition. No tip grooving or weak tip spring, etc. A bit of a mystery.
This high fuel level can lead to temporary fouling. Over time, you can accumulate a lot of fuel into the crankcase too. Though not as bad as a verified leaking petcock, it still adds up.

[gs425e]

hi is this a common problem i have a similar problem to i get no spark on cylinder 2 gsx550 ran when i first cleaned carbs but would not the day after cannot get a spark on 2 cylinder plug even when ive cleaned it and resting on the bike i thought it will be the coil but m be not do all vacuum pet cocks dump fuel to cylinder 2 and if it does fire once i have done the test does the who petcock have to bo replace or just the diapram cheers andy

[Road_Clam]

Cyl 1,3 and 4 are firing great, and the bike runs amazingly well on 3 cylindars.
On the #2 there is spark at the plug, but that cylindar does not fire until it gets fully warmed, and I run it at high speeds. At idle and when cold it doesnt fire at all, or very intermittently.
I have swapped plug wires around with same result. I pulled #2 plug. It is black and wet with gasoline.
Suggestions appreciated.

Clogged #2 carb pilot jet,. Common problem. Look inside your fuel tank, if theres rust, you've got problems, as the rust sediment gets into the carb jets and cloggs them. A lesser possibility is low compression. Buy a compression gauge and check all 4 cyl. befor investing $$$, and guessing.

[Roy]

To see for yourself how angle can effect fuel flow even though there's vacuum present, do a little test.
Dip a piece of fuel line into a gas can so there will be several inches of fuel inside the line. Press your thumb over the top. Lift the fuel line out but keep it reasonably straight up and down. The fuel should stay inside.
But now if you take the top of the fuel line and start bringing it down to create an angle just as it's mounted on the petcock on your bike, you'll see the vacuum weaken and the fuel will flow. So angle changes things.
Even if your petcock is sealing well when the bike is turned off, the amount in the line can still flow into the carb bowl and so cause a high fuel level that can be enough to cause your problem. Carbs 1 and 2 are the ones effected by this because they are on the left side of the fuel "T" and gravity will do the rest. I'm not sure why but carb 2 seems more common to have this problem.
But the reason the fuel enters the bowl is because the float needle valve isn't sealing well.
I've seen many bikes leak while on the side stand but apparently not leak, or not nearly as much, while on the centerstand. I've also seen bikes with brand new petcocks and even non vacuum Pingel valves leak while on the side stand. With a clear fuel line attached I've seen the fuel slowly drain down while on the sidestand but very little or not at all while on the centerstand. The valves looked good in many cases. Only thing that would allow this flow is a float valve not sealing well or something wrong with the float assembly operation. Many of the float valves appeared to be in good condition. No tip grooving or weak tip spring, etc. A bit of a mystery.
This high fuel level can lead to temporary fouling. Over time, you can accumulate a lot of fuel into the crankcase too. Though not as bad as a verified leaking petcock, it still adds up.

Thanks Kieth I will certinly fix this annoying little problem.Its a bugger having to park on the centre stand all the time.:-D