No spark on 2 & 3, GS1000

[Guest]

Hello! I recently purchased an amazing 1979 GS1000. Had not run in three years, new gas and plugs and she fired right up and ran good under 5000 rpm.

Power fell off after 5K do to what I belive really dirty carbs. I noticed the float bowls were real dirty, and the main fuel T into carbs leaked real bad, and tank was real dirty. I cleaned everything, and replaced anything rubber and cleaned the carbs real well. I get it all back together and now I have no spark going to cylinders 2 and 3

My question is this, with the ignition on, I find 12 volts in each of the two wires going to each ignition coil? IS that correct??? Should both wires going into the coils have power like that? Any insight would be much appreciated, thanks.

[rustybronco]

Yes, you should have power going to both ignition coils.

Power goes to the coil, through the coil, to the points and is grounded when the points are closed. When the contact set opens, the coil fires.

[DanielGS1000]

Thank you Rustybronco! That makes sence! I worked on the bike more this morning and found that I actually only dont have spark to #2. Cylinder #3 was getting spark when I checked today.

The coils appear to be original, along with the spark plug wires which are cracked and dried out in some places. Can the coils or spark plug wires just go bad like that?

I would think that if #3 is getting spark then #2 should be getting spark as well because 2 and 3 come from the same coil. Am I wrong to think that?

[azr]

You're right, 2-3 are together but you could easily have to spark to #2 due to what you mentioned, cracked wires and caps. How are checking for spark? It is possible to dig out the stock wires and replace them with new wires and caps. It's rare that a stock coil itself will fail though, they're pretty bullet proof. It has been known to happen but it is very rare. How old are the spark plugs? sounds like the bike needs some good routine maintenance.

[DanielGS1000]

Thanks Arz. The plugs are brand new NGK's from suzuki dealer. I am working hard to do a full maintenance. Just went through the carbs, tank, fuel, and oil system and they are good to go now.

I am checking spark by pulling the plugs and holding them against the top of the engine while I crank the engine with the key on. I noticed today that I got a very week spark from cylinder #2 while holding the plug on the engine and cranking it over, once I instaled the plug and tried to run the bike it ran bad. I noticed that #2 exhaust header pipe was warm/cold while the other three were piping hot. It also seems to me I get a brighter spark from other cylinders...

You mentioned digging out the OEM wires from the OEM coils and replacing them? What dose that take, any tips or recomendations to what wires to buy?

[rustybronco]

First try reaching in the spark plug cap with a small screw driver and unscrewing the small brass screw. Under it you will find a resistor. It should measure around 5K ohms...

[DanielGS1000]

Thank you!!! the resistor in the spark plug boot was really lose. Cleaned the sring and brass washer, tightened the assembly up and she fired right up!

Now to figure out why she smokes out of one of the exhaust pipes...