Has the bike been out in the rain? Wash it recently?
the cavities where the plugs go sometimes fill up with water and you lose spark. there are two drain holes on each side, one at each spark plug port. They get plugged up over time and don't allow collected water to drain. straightened coat hanger works well to clear the drains.
If there is no water present, check the plug caps, make sure you have a nice clean connection where the wire goes into the plug cap. It may be necessary to cut a half an inch to an inch of the wire and screw the cap back into the wire to make sure the you have a good connection.
You'll also want to pull the plugs to make sure they aren't fouled due to a weak spark.
Also if I recall correctly the coils fire 1&3 and 2&4. So if 3&4 aren't firing it's not likely to actually be a coil issue.
As I stated, new coil w/wires= good fresh connection at boot. Used a spark tester, shows a much weaker spark than the other coil. If you are looking at the coils from the riders pos, right coil fires cyl 1&2, the left coil fires cyl 3&4
gee its looking like that may be where the problems at....but id go through things good before going there ...its a rure rear tear down to get at the pluse generator ....but can be done from the center stand possistion ....even the swing arm has to come out for me and my big hands ....
Here is a pdf file of how to test the ignition circuit of a 1100. Might be different than the manual you have. Note that testing the spark units is not simply measuring resistance. It involves measuring a voltage change when grounding one of the pulse generator leads. Good luck.
EJ, an ohmeter cannot always show you a bad ignition coil. Since you have a known good coil and a suspected bad coil, as someone else suggested, swap them and see if the problem follows the coil.
What happens inside of ignition coils is the circuit is still complete and will test ok with an ohmeter, but the insulation has cracked due to heat and or vibration, and under a load the voltage jumps inside the coil and bypasses part of the internal wiring, or partially shorts to ground in the case of the older GL coils. They will still produce a spark, but it is much weaker. I have bought bad coils from my local salvage yard, they always take them back and give me another one till I get a good one LOL. Since I pass right by there on the way to the shop every day,it is no big deal.
Test your circuit going to the coil with a test light with engine running, all the igniters or whatever do is turn voltage on and off going to the coil. The test light should flash on and off rapidly.
Thanks to every one who responded, but let me bring everyone up to speed. Starting at the plug caps, I took them out of the circuit and tested with a 5K ohm reading on each. The circuit in question (3&4) cly has a new coil (now I know I could get a defective part, but the current coil is doin the same as the old coil) to top that off, I swopped coils and the problem does not follow. Leading me to belive the coil is good. As to voltage @ the coil (input) it is the same on both coils. On up the line @ the spark unit, again with all things being equal, I swapped them with out with the problem not changing (still at 3&4) so spark unit good. Again I also followed the test procedures in manuel and found no ill results. I did the grounding of the pulse gen lead test with good results. Ohm tested the pulse gen with a reading of 570 ohms @ 80 degrees (spec is 530 +/- 50 ohms At 68 degrees). Here is another thing that troubles me, I connected a spark tester to the spark plugs, 1&2 fire great, 3&4 is a noticable weaker spark. Plus when engine is reved to 3K rpm, spark gets weaker and at 3500 rpm, spark goes away compleatly for both 3&4 cyl. Am I looking at pulse gen issue? Again thanks to everyone for your help
Yes, it is very possible you have pulse generator problems, if, your CDI unit is good. Good with a ohm meter is not the best testing method. If that is the tool you have available, it is what you have to use, however. If you have a regular unpowered 12 volt test light, you can test the voltage going to the coil when the engine is running and try to duplicate the problem. If the light quits flashing, you know you have either a CDI ign going out, or the pulse generator going out. Since you have isolated the problem to the primary side of the ignition circuit (CDI or pulse gen) I would begin testing in that direction. I would not rule out a bad connection somewhere for sure.
To test the pulse generator, disconnect it from the CDI unit, set your volt ohmeter to AC voltage scale to a low setting, spin the engine over with a good battery. Compare the readings, since you have two pulse generators. Compare the readings. See what you find and get back to us.
Yes, the CDIare the spark units mounted up under the false tank on the left side.
As the instructions show for using an ohmmeter, unplug them there is best.
I forgot to tell you that dependingon the sample rate on your volt ohmmeter, your findings of AC voltage should vary some, but you should get a reading. The more expensive meters have shorter sample rates that show the voltage up on the screen much faster so would vary more. This is why I cannot give you a voltage reading that is is definetly good.
What you want to see if both are good is a voltage reading that is the same. If one is way less than the other, using the same voltohmmeter, the low one is bad, or in your case, going out.