81 650H ignition for dummies

My 81 650H has factory electronic ignition. No longer satisfied that my troubles are entirely carb dummy related, I started digging into another area I know little about. 

I pulled my plugs and 3 were sooty, and the #2 was wet with gas, so I thought I should look at ignition. #2 was definitely spitting/popping/backfiring at times, along with #4. Before testing resistance, I checked the #4 for spark and it "looked" good, for what ever that's worth. 

I then measured resistance on my #1 and 4 coil, primary is at at 2.4 and secondary (without caps) at 12.3 resistance. The 5K NGK Caps were 5.25k (1) and 5.5k (4) 
I measured resistance on my #2 and 3 coil,primary was 2.6  and 2ndary was also 12.3.  Cap 3 was and NGK at 4.4K and cap 2, which I just discovered was different from the other 3 (a NICHIWA 5K), was all over the place. Sometimes it would settle at about 4.2, but it would also jump up over 100 at times, and everywhere in between. I kept measuring because I wasn't sure if I was just not getting good contact, or if the resistance was really haywire. Kept getting the same results.  I then tested plugs 1-3 for spark. 1 and 3 looked good, but 2 didn't have any spark. 

Maybe worth mentioning that I have BR7ES resistor plugs, and have read on here that having both resistor plugs and caps might not be a great thing. IIRC when I went to buy B7ES they were special order locally. 

Correct me if I'm wrong but it seems like my primaries and secondaries are OK, at least resistance wise, and I have a bad cap, or maybe all my caps are far enough out of spec to replace them? Since I'm replacing one I guess I should do all 4. 

I'm sure there's more advanced testing that can be done but I think they only thing I have the knowledge and equipment for is to test the pickup coil resistance, which is next on my list

I agree with what many here have indicated regarding resistor caps and /or plugs. One but not both. I actually don't use either. It is my understanding the use is mostly to combat RF interference.There maybe other reasons, and I would think others will chime in. I learn something new here all the time.

Anywhere in the region of 5kohms is ok for the caps, when you checked coil resistance did you also check for continuity to the laminated iron core (mounting post) this should measure as infinity. As well as checking the resistance of the pick-up coils you can check the system is functioning by placing an LED across the coil primary connections (polarity sensitive) when you crank the motor the LED should "pulse"

2 & 3 fire together, so since you have a good spark on 3, that indicates something is wrong with the #2 HT lead.  I'd replace all of them.  7mm copper core wire is pretty cheap.  If you squirt some WD-40 inside the outer wire sheath, you can pull it off the old wire and install into your new ones.  

Wookie58 wrote:

Anywhere in the region of 5kohms is ok for the caps, when you checked coil resistance did you also check for continuity to the laminated iron core (mounting post) this should measure as infinity.
As well as checking the resistance of the pick-up coils you can check the system is functioning by placing an LED across the coil primary connections (polarity sensitive) when you crank the motor the LED should "pulse"
 

I believe I did that continuity test too. I also tested voltage to the coils and not surprisingly found it a bit low, at about 11.5v.   So I could probably spend all winter cleaning connections but I won't be here all winter. 

I presume you mean an LED test light? NOt sure if I have one but I might. If i don't I can pick one up tomorrow along with a new plug cap. If the other 3 are within tolerance I think I'll just get another resistor cap for now. I

Nessism wrote:

2 & 3 fire together, so since you have a good spark on 3, that indicates something is wrong with the #2 HT lead.  I'd replace all of them.  7mm copper core wire is pretty cheap.  If you squirt some WD-40 inside the outer wire sheath, you can pull it off the old wire and install into your new ones.  

 

I think its just the #2 cap that is janked.  Although I'm contemplating replacing all 4.

The pickup coils pass the multimeter tests in the FSM. So I think I will replace the cap or caps and give it another test start, and if I still have trouble guess its deoxit time. 

It is perhaps worth mentioning that when I first got the bike it had low compression. I haven't tested it lately because while I have run it a fair bit in the garage I really haven't ridden it any distance so I don't know if it has been run enough to overcome years of not running. I think its under 15 miles since I got it. Maybe I will check the compression again before I give up for the winter