Running on one cylinder.

C Squared · December 11, 2006, 08:54:24 PM

My 1990 GS is only running on one cylinder. It's getting spark and sounds like it wants to turn but still only runs on the right cylinder.

Float height checked.
Air mixture screws checked.
Carbs cleaned.
Spark checked. Even switched the coils. No change.
It's getting fuel.Plugs checked.
Compression is good.

Non-firing cylinder (left) plug is black and wet.

Any ideas? Thanks!

annguyen1981 · December 11, 2006, 09:00:13 PM

My guess is that your left cylinder isn't firing.

Sorry...

I'm working on (or supposed to be) TWO class presentations that I just started... Both are due this week.

scratch · December 11, 2006, 09:03:46 PM

What do you mean spark was checked?

Did both sides have spark?

espm1000 · December 11, 2006, 09:07:23 PM

If you didn't already replace both the plugs with some new ones. The NGK's come pre-gapped. That may not fix it, but it's a start. When you say you rechecked the air mixture fuels does that mean that you screwed them all the way in and then out to the stock setting? A plug that is black and wet tends to mean that it is running way too rich.

http://www.aa1car.com/library/cm1196.htm

GeeP · December 11, 2006, 09:07:48 PM

I take it that it has a spark on the dead side, compression is good and the plug is wet... It should run!

I might check the carbs for water from your tank.

No water? Dry off your plugs with compressed air, motor over the engine w/ the plugs out a few revolutions and try again.

Another thought is you might have a stuck slide or needle. It might be getting fuel, but the mixture might not be combustible.

That's off the top of my head...

Oh, Welcome!

C Squared · December 11, 2006, 09:42:42 PM

Quote from: scratch on December 11, 2006, 09:03:46 PM
What do you mean spark was checked?

Did both sides have spark?

Correct. Both sides have spark.

C Squared · December 11, 2006, 10:07:13 PM

Quote from: espm1000 on December 11, 2006, 09:07:23 PM
If you didn't already replace both the plugs with some new ones. The NGK's come pre-gapped. That may not fix it, but it's a start. When you say you rechecked the air mixture fuels does that mean that you screwed them all the way in and then out to the stock setting? A plug that is black and wet tends to mean that it is running way too rich.

http://www.aa1car.com/library/cm1196.htm

Brand spankin' new plugs. I guess I'll go through the carbs again. Thanks!

Egaeus · December 11, 2006, 10:35:48 PM

Have you checked your valves? Balanced the carbs?

Try running on the left cylinder only and see if it will run at all. If so, it's probably one or both of the above.

C Squared · December 11, 2006, 10:41:13 PM

Quote from: Egaeus on December 11, 2006, 10:35:48 PM
Have you checked your valves? Balanced the carbs?

Try running on the left cylinder only and see if it will run at all. If so, it's probably one or both of the above.

Left cylinder won't run at all. I'll check the carb balance when I run through the carbs again. Thanks for all the replies guys. Keep the suggestions coming.

Jughead · December 11, 2006, 11:42:56 PM

Go to your Dealer and Get an NGK or Equivalent Non Resistor plug Cap(s).That may be your Problem.Your Bike is a 90's Model and the Resistors in the Caps Have Probably built up too much Resistence over the Years.If your Running Resistor Plugs then your getting too much Resistence.You actually do not need Any resistence it is only to Cut down on Radio Interference.
Remember if it's Black your not getting a Complete Burn.You are getting Spark but not Enough to Burn Hot Enough to Keep the Plug ETC. Clean.More than Likely IF you don't see a Spark your Plug is Fouled out and the Spark is Going Straight to Ground from the Electrode to the Oily mess on your Insulator.

Actually I have Preached the Resistor Cap Issue on all of the Boards that I belong to until I have Turned Blue in the Face.The Only Guys that Have Listened are the ones that Have Had Nothing but Problems thinking that it was the type of Plugs they were Running or their Carbs Being Dirty or their Timing Being Off.ETC.ETC.ETC. Everything that they tried it would be the same thing until they switched the Plug Caps.75% of the time they would Thank me in the End when they Ditched their Resistor Caps.

The Buddha · December 12, 2006, 06:44:48 AM

Hey mine too ... the savage I rode in on today ... ran on 1 cyl the whole freaking way from the time I started it, to when I got in to work ...

I just could not get it to run on 2 cyls. It ran good though. Made 90 clicks and stops and starts were peachy. never stalled once ...

So yea ... join the club

Cool.
Srinath.

The Buddha · December 12, 2006, 06:47:36 AM

Oh yea ... you are sucking fuel through the petcock diaphragm. Cap the vacuum line and cap the petcock and run it in prime. see what that does. Then fix the diaphragm in the frame petcock.
And no resistor caps aren't hurting you. I ahve seen plugs (especially NGK's) that were total sheite right out of the box.
Cool.
Srinath.

C Squared · December 12, 2006, 10:02:52 AM

Quote from: seshadri_srinath on December 12, 2006, 06:47:36 AM
Oh yea ... you are sucking fuel through the petcock diaphragm. Cap the vacuum line and cap the petcock and run it in prime. see what that does. Then fix the diaphragm in the frame petcock.
And no resistor caps aren't hurting you. I ahve seen plugs (especially NGK's) that were total sheite right out of the box.
Cool.
Srinath.

I'll try that but I actually ran fuel from the tank directly into the carbs with no change. Right cylinder only kicks over. But I also replaced all my lines after that. So I'll try again. And as far as the plugs I bought more than a few and tried switching them out. They always work on the right and not the left. Meh. Dammit.

C Squared · December 12, 2006, 01:22:25 PM

Quote from: seshadri_srinath on December 12, 2006, 06:47:36 AM
Oh yea ... you are sucking fuel through the petcock diaphragm. Cap the vacuum line and cap the petcock and run it in prime. see what that does. Then fix the diaphragm in the frame petcock.
And no resistor caps aren't hurting you. I ahve seen plugs (especially NGK's) that were total sheite right out of the box.
Cool.
Srinath.

I capped the vac line and petcock and tried to run it on prime and it would not even start. Tried some brand new plugs. No change. Dammit. time to go through the carbs again....

The Buddha · December 12, 2006, 01:51:15 PM

OK sorry this reply was not including your previous post. I sat with this in the editor for over an hour while I was going other sheite. I'll look and think and tell you.

OK then, in that case - crank trigger. Its possible to run the left one off the right trigger. You need 3 wires with spade female on one end and male on other. The trigger wires should be swapped but not the ground and oil light. Then run right sparkie on the left coil and vice versa. That will make the left coil fire using the right trigger and it will be routed to the right cyl. That way you can eliminate everything but the trigger.
Cool.
Srinath.

Egaeus · December 12, 2006, 02:09:44 PM

Don't forget to check the valves while you have the tank off.

Chuck · December 12, 2006, 02:30:21 PM

Pull off the carbs, and disconnect the right plug. Squirt a very small amount of starting fluid in the left intake. Crank it.

Disconnect the left plug and reconnect the right plug. Squirt the same amount in the right intake and crank it.

If the behavior is the same, you can focus on the carb. If the behavior is different, first try it again and make sure, and blame it on electrical or valves. Swap plugs, swap coils. If the problem doesn't switch sides then it's not electrical (unless the electronics are hosed).

Do a compression check.

Um..... maybe some other stuff.

C Squared · December 12, 2006, 06:13:04 PM

Quote from: Chuck on December 12, 2006, 02:30:21 PM
Pull off the carbs, and disconnect the right plug. Squirt a very small amount of starting fluid in the left intake. Crank it.

Disconnect the left plug and reconnect the right plug. Squirt the same amount in the right intake and crank it.

If the behavior is the same, you can focus on the carb. If the behavior is different, first try it again and make sure, and blame it on electrical or valves. Swap plugs, swap coils. If the problem doesn't switch sides then it's not electrical (unless the electronics are hosed).

Do a compression check.

Um..... maybe some other stuff.

Swapped coils and plugs trying to sort this out. No change. I'll try what you suggest though. Maybe something will come up. Thanks!

The Buddha · December 13, 2006, 10:09:05 AM

Your problem then isn't the coils. Its the wiring or the crank trigger.
Oh wait a sec ... auxillary ground. Yea that ... disconnect it and you lose a cyl. Different bikes you lose different cyls.
Cool.
Srinath.

Chuck · December 13, 2006, 10:12:46 AM

Did you try the starter fluid squirt test? I was convinced my carburetor was clean as a whistle until I tried that and realized that the non-firing cylinder would fire the same as the other one with some starting fluid. I went and cleaned the carb like two or three more times (it had been sitting for about 3 years with gas in it) and got it running like butter.

News:

Running on one cylinder.