Ignition coil

[Thadbaker86voyager]

Hey was wondering if you loose an ignition coil does it drop two cylinders, or one? I am thinking the coils are one coil, feeding two cylinders. Not two coils in one package. Is that correct?

[Nails]

One coil feeding two cylinders, at the same time. (It fires on exhaust as well as compression, like most bikes.) The cylinder pair served by one coil fire 180-degrees apart.

Despite different PNs, the coils are identical except the mounting bracket, which generally reverses. I carry one spare coil and one spare wire. I think new stock coils are hard to find.

[Thadbaker86voyager]

Thanks! That’s what I was thinking, just needed a second opinion! Lol! Got first ride in yesterday, it was great! After about an hour, developed a slight miss on one cylinder. Thinking plugs or wires. Was able to ride home no problem, just the occasional miss on one cylinder.

[cranky]

iridium plugs made a noticeable difference to me!! .... just sayin'....

[Thadbaker86voyager]

Thanks, Cranky, I am going to try those. Standard plugs in it now.

[ekap1200]

Thanks! That’s what I was thinking, just needed a second opinion! Lol! Got first ride in yesterday, it was great! After about an hour, developed a slight miss on one cylinder. Thinking plugs or wires. Was able to ride home no problem, just the occasional miss on one cylinder.

check out the resistor plug cap's . Its easy enough to do with a good known muti-meter. It is a deep dive in the pool to get to the coils, NGK caps are not at a bad price from vendors such as partzilla or bike bandit and come with the 2 rubber boots also , ( not so from Ma Kaw stock ) Had that happen to me last fall, 1-4 were giving me a slight miss.
Gene Kap

[triton28]

Ignition coil failure shows up after the coil heats up and becomes an open circuit. 2 cylinders will be effected so it is very evident when a coil does go bad. Plug caps should read between 4990-5020 ohms resistance when checked with digital multimeter.
As Cranky said Iridium plugs are so much better performing than the standard plugs.The difference is noticeable.
Dave

[Thadbaker86voyager]

Thanks everyone I hadn’t thought about the plug caps, will have to check them also!

[SgtSlag]

My '79 Honda had weak coils from the factory (known issue). Replacement/upgrade coils were around $40/coil, back in 2008! Tried NGK Iridium plugs instead (far less $$ out of my pocket). They were amazing: engine fired, and was running, almost instantaneously! Never had to grind the starter for 5-7 seconds, wait 10 seconds for the starter to cool, then grind it again, to start that bike, after installing the Iridium plugs...

I liked the performance so much, I installed them in my XII, as well. I paid around $8-$10, per plug. Worth it, IMO. The XII seems to have much stronger coils installed, from the factory. The Iridium plugs, however, will almost never fail to fire -- they provide piece of mind. They're not a 100% guarantee, but they should shore up other weaknesses in the ignition system, if any, at least for a while. Cheers!

[ekap1200]

I see you had joined back in 2016. Have you kept up on draining the carbs, adding Sea-Foam, and all the other maintenance items.... Talking to the many here that are paid professional's , they have not seen issues with the coils . They are mounted in a very well air cooled area, and even when the bike is shut down at the end of the day, they are not directly over the heat of the radiator or engine.
Gene

[Thadbaker86voyager]

Yes I have ran sea foam, drained carbs, and stabilized fuel during the winter. However this was the first ride after storage, so fuel is a suspect for sure. At this point have changed plugs and checked spark plug wires and caps. All checked fine there. Drained carbs on paper towels, but didn’t find anything, except gas. Fuel Smells/looks good, not stale. Changed fuel filter and checked fuel line routing for kinks. Fuel pump and fuel flow checked out. Have not load tested coils, per service manual. Haven’t had a chance to ride and try it out again since plugs etc. hopefully will be able to take a ride tomorrow and see if miss is gone. I am kinda doubting coils, thinking the missing would have been more serious if a coil was bad. Thanks for continuing to help with trouble shooting my problem.

[Nails]

I went through a similar problem. Did a ton of stuff, mostly overdue maintenance like completely dismantling the carbs and chunking them in a sonic cleaner. I chased jetting (had moved the newly-bought bike to a much higher elevation) and screwed with the pump and filter just like you. I balanced the carbs. I removed the valve covers -- the valve train looked fine (gasket leaked anyway). I found a damaged plug (porcelain cracked), but replacing them didn't fix it. I swapped spark wires. And yes, I replaced the coils (Chinese, saved old stock ones for spares). Nothing worked.

It was a bitch to figure out partly because the missing wasn't too pronounced (at first), it was worse or better from day to day, it seemed to go away at speed (I could get 46mpg on 60mph roads), and I couldn't reliably test the compression (couldn't get any of four different compression testers in there right). I had several confounding problems along the way like a funky gasket that interfered with a carb float -- this bike hadn't really run right since I bought it. Acting on a mere hunch (inspired here), it turned out to be stuck piston ring(s).

My first clue was the damaged plug. I ran a few days on the mostly-dead dead cylinder, and I think that caused the whole problem in the first place. (Well, the bike had sat a long time before I bought it.)

Given what you already looked at ... If it's one particular cylinder misfiring (one exhaust pipe slow to get hot), then I suggest the following: take out all the plugs and remove an engine side cover to get at a bolt to turn the engine over. Put the problematic piston all the way down, and then fill it with Seafoam. Let it sit until it leaks into the crankcase. (Just an hour for mine, my second clue.) Maybe do this a couple times, turning the engine over a few times between. Put it back together, deal with your overfilled crankcase, and fire it up to see if the miss is gone.

(For this testing, I left that ton of Seafoam in the crankcase -- just drained the volume down. I could tell right away that the miss was gone -- didn't need to drive anywhere. THEN I changed the oil. And man, that oil sure did smell rank!)

This site has a few threads about stuck rings. I've never had that problem with any other motor, ever. Therefore, I think XII are prone to stuck rings.

[Thadbaker86voyager]

That is something to consider. Sea foam in the cylinders would definitely free things up! I have ran this bike for several years with no problem. It ran about an hour of mixed riding conditions before the slight miss started. All spark plugs were the same color. Normal color for good heat range and correct mixture. I would think if it was a spark plug, electrical problem there would have been a plug that was wet or had soot on it. I am starting to think that even though I didn’t get anything out of carburetor bowls except gas, that maybe something is in a jet on one carb causing it to be slightly lean and create an intermittent miss. Will know more when I ride it again and see if the miss is gone or not!

[Nails]

It ran about an hour of mixed riding conditions before the slight miss started.

That to me doesn't sound much like a stuck ring.

I would think if it was a spark plug, electrical problem there would have been a plug that was wet or had soot on it.

Or a big crack in the porcelain.

even though I didn’t get anything out of carburetor bowls except gas, that maybe something is in a jet on one carb causing it to be slightly lean and create an intermittent miss.

That should show in the plug color.

Just draining the float bowls doesn't really say very much. There's lots of things that can go wrong with the carbs: fuel level, clogged circuits, sticky piston, leaking diaphragm ... it's hard to get them right. Lots of threads here about this. Also https://gadgetsfixitpage.com/article.ph ... carburetor.

The easy solution would be to swap all your carbs with Carl Leo for a set that he has gone through. If he's actually still in business. This could make sense even if you didn't have a miss.

Back to the basics: you need compression, spark, and fuel.

[Thadbaker86voyager]

Load tested coils and they passed. Buttoned it back up and took a test ride. Rode same route, doing everything as much the same as the first time. Ran perfectly! Then rode about 30 minutes more, still ran perfectly! Probably was just as simple as a spark plug going bad. Am glad I checked out everything else while I had it apart. Thanks to everyone for all the help and brain storming!

[ekap1200]

Thanks! That’s what I was thinking, just needed a second opinion! Lol! Got first ride in yesterday, it was great! After about an hour, developed a slight miss on one cylinder. Thinking plugs or wires. Was able to ride home no problem, just the occasional miss on one cylinder.

Thad, when you wrote " just the occasional miss on one cylinder " was this at idle or running down the road ? Also did you - or - are you checking the carb sync. ?
I have followed this thread and see your running down the road nicely now. Engine just needed a good heat cycle , and fresh fuel passing thru it.
Gene

[Thadbaker86voyager]

It started the slight missing after about 30 or more minutes of mixed riding. Missed at cruise and load, but didn’t seem to miss as much, or at all at idle. Which makes me think now that’s more like starving for fuel on one carb. Anyway I am glad it is running correctly now. It has always ran perfectly, until that missing.

[ekap1200]

It started the slight missing after about 30 or more minutes of mixed riding. Missed at cruise and load, but didn’t seem to miss as much, or at all at idle. Which makes me think now that’s more like starving for fuel on one carb. Anyway I am glad it is running correctly now. It has always ran perfectly, until that missing.

Good to hear. put some miles on it and run out the old fuel. See if your mileage per gallon has drasticlally changed. Let it get some heat up with some new fuel and if all seems good give it one more carb purge and maybe at least do a carb balance vacuum inspection for the season and go riding.....
you stated that " I ran sea foam, drained carbs, and stabilized fuel during the winter " Does that mean you added SEAFOAM and used another product to stabilize the fuel in the tank also ? I have had issues with other products used for EXTENDED storage getting a gloob of goo in the bowls that needed just time and good fuel and some miles to clean out. As Bill-O would say " If it ain't broke don't fix it " I would say that if it ran great when you turned the key off for the season , what and how can it break down .....
I can only assume you did look at the air filter for varments looking for a winter home ???
Any how hope it clears out and goes back to running like it always has ran. Are you going to the Rally ? The more the merrier

[Mr Jensee]

I need to check the resistor plug caps. I have a loud hash noise in my radio now when I get some distance from the station. Not there when I am near an FM tower.

[Thadbaker86voyager]

Hi ekap1200,
I only used sea foam in fuel, as stabilizer and in fuel as a cleaner. No other products. I have a hardware cloth type wire, 1/4 or 3/8th inch, something like that in the air filter intake to keep critters out in the off season. So no problem with air filter. It has been running perfectly since the plug change. So all is well now. Have ran it 200 or so miles now with no problems.