Cylinder 2 DEAD

[wad650]

Bike fires and idles, exhaust 2 is cold.


We have checked spark to all plugs by touching them to the crackcase all seem to have adequate and consistant spark. Is there any way to check a coil pack for weak resistance?

What other causes could there be for dropping number 2 cylinder?

We thought this issue was with the carbs since the bike ran rough since we got it so, we rebuilt the carbs and we are having the same issues now. We are testing on an aux. tank so petcock and fuel filter is not an issue.

We believe it is an electrical issue because it seems to be ok and then just drop number 2 ( cylinder that is not human number 2 LOL) but, number 2 will intermittently kick in.

We have tried to sync the carbs thinking that was the issue but, with the cylinder dropping out its hard to get the bike to idle right.

Any help would be great.

Thanks
Walker Boys

[Nessism]

Did you do a compression check? If not, you might want to consider it. Of course, if you haven't adjusted the valves in a while that would be a good idea as well.

[Steve]

First of all, what bike are we talking about? The year is important.

To help diagnose, swap the plug leads for cylinders 2 and 3 to see if the problem follows the wire. Could be a bad wire or plug cap.


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[wad650]

First o all, what bike are we talking about? The year is important.

To help diagnose, swap the plug leads for cylinders 2 and 3 to see if the problem follows the wire. Could be a bad wire or plug cap.


.

Sorry, it is a 1981 GS650G.

[pvtschultz]

Could also be a plugged choke fuel circuit in the carb bowl. If the engine gets really warm and it still doesn't come around, could also be a lean air idle screw setting.

On my GS850G 1 and 3 are common as well as 2 and 4 IIRC...

[relic-rider]

Whenever it is just #2 on the CV carb bikes, you should always check the petcock first. If the diaphragm is leaking, it will suck excess gas into #2 cylinder and flood it, causing the plug to foul out. Some plugs will fire fine outside the engine, but put under compression and excess gas, will misfire or not fire at all. Put in a new plug, put the petcock on prime(if it has this option), and plug the vacuum line on #2 and give it a try.

[Jaguarjoe]

Is there any way to check a coil pack for weak resistance?

I just measured mine on my GS550L. 33,000 ohms between plugs 1 and 4, 35,000 ohms between plugs 2 and 3.

[wad650]

Whenever it is just #2 on the CV carb bikes, you should always check the petcock first. If the diaphragm is leaking, it will suck excess gas into #2 cylinder and flood it, causing the plug to foul out. Some plugs will fire fine outside the engine, but put under compression and excess gas, will misfire or not fire at all. Put in a new plug, put the petcock on prime(if it has this option), and plug the vacuum line on #2 and give it a try.

We are running an aux tank which is a little 2gal tank with just the one line going to carb two from the tank. It has always been a problem since I had the bike the guy I got it from said that it need the carbs cleand so I bought the rebuild kits and rebuilt them and it is still having the same issue. That is why we think it is electrical. But, I will be going to Auto Zone tomorrow and getting the compression tool and I will check comp.


If I pull one spark plug cable should the bike still run?

I noticed that when I took the cable off of plug 2 and touched it to the head there was a stong sparking coming out of the boot part of the plug wire (the plastic piece) is that good? I tried it with the other wires and they did not do that.

Thanks
Walker Boys