2 cylinders stop running

[mike10]

I have 2 cylinders that stop running. Sometimes when it idles most of the time running down the road, the speed doe's not seem to matter. I cleaned all the electrical connections and I thought that fixed it. But now it's doing it again. Why would it be only 2 cylinders? And so random. Can a coil start and stop working? It starts easy . Sometimes it cranks over hard, I think that problem is in my starter. But if the engine turns over at all it starts. I have had 2 plug wires pulled off hit the starter to check for spark and it would run on the 2 remaining cylinders. Anyone else had a problem like this? I think I have checked everything I can. I'm stumped.

[tkent02]

Which two?

[Billy Ricks]

If it's one and four or two and three you have a bad coil, signal generator, or igniter. I'm betting coil. If it's one of the pairs I can post up some testing procedures that should help.

[tkent02]

If it's one and four or two and three you have a bad coil, signal generator, or igniter.
.

Or a problem with wiring going to these items.

[Billy Ricks]

Or a problem with wiring going to these items.

Could definitely be the cause. Maybe just a loose coil wire.

[tkent02]

Corrosion...
Or PO induced problems.
Most POs have very limited knowledge of basic electricity, but it does not seem to limit the number of modifications and improvements they attempt.

[mike10]

More Tinkering

Ok, I unplugged the coil wires from #2 #3 from the harness. No power to that coil, it started on #1 #4. So I unplugged the #1 #4 coil from the harness. Plugged the #2 #3 back in. It would not start. Put everything back.Started the engine. Then pulled the plug wires off each plug one at a time. If I pulled off the #1 or #4 it would kill the engine. It would keep running if I pulled the #2 or #3 off. So I'm saying the #2 & #3 are the problem. But sometimes holding the plug wire in my hand from #2 & #3 I would feel a shock. So I think either the coil to #2 & #3 is working off an on, or the coil is getting power off and on. My test light always shows power at the coil plug on the harness when the key is on. I never checked it when it was running. Can you put new ends on the spark plug leads or do you have to get a new coil? Also, if it was the ignitor or the R/R or that electronic thing that replaces the points,(I can't remember the name of right now.) Wouldn't all cylinders be dead? Even if I put a new coil on and it runs fine, I can't be sure it's fixed. Could be this intermitent problem just isn't happening right then. I need to get Beer and Drink on this a while. thanks for the suggestions.

[tkent02]

Read some threads about troubleshooting ignitions, there are a lot of them.

Very simple stuff, just work your way through it. You most likely have some kind of connection problem, although it could be a failed component.

These bikes ALL develop connection problems after thirty years of neglect.

Spark plug leads, ignition wires, anything else along the way could need attention. The charging system connections all corrode, and the systems can and will fail expensively if the corroded connections are left unrepaired and the bike is run anyway.

[Billy Ricks]

You should always have power to the coils with the key on. The signal from the ignitor is actually ground. A real quick test you can do on the coils is to check resistance. On the primary side, the side with the leads from the ignitor, you should see 3-5 ohms. On the secondary side put one probe in each plug wire for 2 and 3 then 1 and 4. You should get 30k-50k ohms. The signal generators which replace the points should measure 130-200 ohms. I can give you a test for the igniter but I'll have to get on the desktop PC for that. I have the info written up in a Word document.

[BassCliff]

Hi,

Here are a couple of links that might give you some ideas...

Testing The Ignition System - A pretty thorough write-up by Mr. Matchless.

Simple Coil Repair - I found a busted wire on a coil one day after losing spark on a couple of cylinders.

Check your plug caps and spark plug wire connections.


Thank you for your indulgence,

BassCliff

[Steve]

One other question that you asked and hasn't been answered yet:

Yes, you can remove the spark plug caps (they screw in), trim back about 1/4" of the wire and screw the caps back in. Highly recommended to do this, especially if you are not getting that 30-50k ohm reading that Billy Ricks mentioned.

.

[rustybronco]

Every measurement that I have made or seen on the stock GS coils has been in the range of 11-13K. PLUS the two plug caps @ 5K ohms EACH; for a total "plug cap to plug cap" range of 21-23K ohms.

on the coil I measured Saturday, the coil resistance was around 12K and the two 5K plug caps had measured somewhere around 8.9K each; for a total cap to cap resistance of 30.1?? K ohms.

I would consider any "plug cap to plug cap" measurement over 25K suspect, which would require further investigation.

[850 Combat]

I did not see what year bike. Does it have an electronic ignition? If not, it can also be the points or condenser.

Coils can fail intermittently, although in my personal experience it has been related to temperature, where they short out when they get warm. I have had relays do that too.

On a GS, you can actually change the wires to the coils to switch the 1/4 to the 2/3 and see if the opposite side has the problem. If it does, its coils. If it stays the same, the problem is upstream of the coils.

[Billy Ricks]

I did not see what year bike. Does it have an electronic ignition? If not, it can also be the points or condenser.

Coils can fail intermittently, although in my personal experience it has been related to temperature, where they short out when they get warm. I have had relays do that too.

On a GS, you can actually change the wires to the coils to switch the 1/4 to the 2/3 and see if the opposite side has the problem. If it does, its coils. If it stays the same, the problem is upstream of the coils.

I think he mentioned signal generators somewhere, just didn't know what to call them. The factory manual does call for 30k-50k resistance on the coils measured with the plugs in place.

[mike10]

1980 gs1000

It has electronic ignition. I will trim the Plug Leads and re-do the caps I did not know how to do that, till now. After switching that #2 & #3 coil with a different one I had, it has been running great. I like the Basscliff web site I 'm going to read that and do some tests. Thanks everybody . I'm getting less Dumb all the time.