Running on 2 cylinders

[uk gs nut]

Strange problem occurred on Sunday. Out for a ride up to St Marys loch bike was running great as normal, but about 200 miles into run it missed a little. Then 10 mins later it dropped onto 2 cylinders, pulling plug leads off as I went it was 1 and 4 not working. Stopped and was going to have a look switched off and on again and it fired on all 4, never missed since. Tonight I removed fuel tank to check connections and voltages etc and all ok. Bike is a 79 GS1000. Dyna S. standard coils with relay mod. SH775. Anyone have similar issue ?

[Steve]

A couple of quick things come to mind:

1. Check that the plug caps are screwed tightly to the wires.
1a. Since you are going to be playing with the plug caps, why not just remove them, snip about 1/4" from the end of the wires, then screw the caps back on to some fresh wires.
1b. Since you are going to have the caps off anyway, use your ohmmeter to check the resistance. Should be about 5k ohms. The resistors are known to have a finite life, the exact duration is highly variable.

2. Verify that the primary leads to the coil are tight on the terminals.

.

[uk gs nut]

Thanks Steve, been there done that. 1 and 4 plug caps were renewed at begining of year and 2 and 3 last year. All plug leads were replaced also. Cantankerous old bike.

[Brendan W]

Are you sure the coil supply plugs are OK ?
The stock items can look clean at the pins and the wires outside the plug look good but inside there can be a mess of corrosion.
I have an old Piranha system. After I dealt with the coil plugs I found a loose pin in the multi-plug at the ignitor. Tracked it down by wiggling the plug at idle.

[uk gs nut]

Brendan all good and clean with dilectric grease. I will remove crash bar and ignition cover to chech Dyna pick ups tomorrow.

[Steve]

Thanks Steve, been there done that.

OK, good to know. With the failure on 1&4, I was just going with the obvious (and easy) stuff.

.

[60ratrod]

I had issues with a dyna unit on my 650g earlier this year. ended up being the left pulser coil for the 1/4 coil. it would be fine, then suddenly drop off line. usually I would end up having to pull that coil off the plate and then put it back on. in the end I replaced the dyna unit. just something to try if it drops one coil again.

[uk gs nut]

Thanks ratrod. I never got to look at the bike yesterday. Should get to it tonight, downloaded a test guide from the search function. Will post results later.

[60ratrod]

you can start by metering out the signal wires. if everything is good with the dyna, you should see at the signal terminal of the coils .8vdc-1.2vdc iirc. if not, you'll see .2vdc-.3vdc at the signal terminal. if you find the low voltage, then pull the low pulser coil off of the plate and then reattach it, make sure you mark where it was before you remove it. this should restore the voltage, and tell you that the dyna pulsers are bad/going bad

[geol]

I might trouble shoot this issue a bit differently.

First, I would consider the 1&4 ignition had an issue as have some of the others. I would FIRST ensure that the two pin plug for the 1 & 4 coil has voltage with the key on. If it does, I would then swap the connectors from the 1 & 4 coil to the 2 & 3 and also reverse the plug wires. This would tell me if the issue was coil related. If the problem stays on 1 & 4 coil, then suspect the coil. If the problem moves, suspect the pickup coil or wiring from the Dyna S. Someone suggested removing/replacing the pickup coil and I can't really see how that would make a failed component come back to life but is worth a try. I have used a lot of Dyna S ignitions and never saw a failed pickup coils so never tried it. Electrically I think they pretty simple and it may be that Dynatek might make a single one available or replace yours for free, depending on the age of the unit.

[uk gs nut]

Thanks everyone for the replays, the dyna system is around 10 years old. I fitted it due to condenser problems, all I can think is wrong is maybe there was a connection issue on low tension wires and with me disconecting thins it rectified itself. I will have another look later, been busy with work.

[uk gs nut]

Progress report. I found the problem, the low tension wires on the 1-4 coil live wire had a break in it. It was under the sheath at the cable clamp on coil mount, only found it when I unbolted the coil. I will give it a test ride at the weekend.
Thanks for all the tips .

[60ratrod]

Glad to see this may have been an easy repair. Geol, i suggested lifting the pulser coil and reinstalling it cause on the first dyna s i put on my 650g i pulled the left coil to inspect it when the issue first arised, and when i reattached it, it came back. I ended up replacing that dyna cause it gave me nothing but issues. And dyna only warranties their components for 1 year