Hello all,

I changed (3/4) spark plugs on my 1985 K100 two weeks ago since I couldn't manage to get the spark plug cap (boot) off one of the plugs. At the time I didn't want to risk damaging the wiring as I was going on a trip the next day and the engine was running fine the way it was. I was just doing some springtime maintenance before hitting the road. I now have more time to work on the bike, which is still running fine, and want to change that spark plug. I know that I could replace the wiring, caps, and coils. However, the bike still has the original caps on it and I want to preserve that if at all possible. 

Anyway back to the problem description;

When I was pulling the caps off the plugs, it was very difficult to dislodge them. After pulling the first I saw quite a large amount of corrosion built up on the spark plug terminal. It did have the screw on cap so I don't know why it would be corroding there, except maybe from age?? I was able to dislodge 3 of the 4 and sprayed them with contact cleaner before hitting them with a brass brush to clean off the metal connection. I have the bike on the center stand and am currently almost pulling it over trying to pull the last cap off. It can rotate freely but is unable to come off the spark plug. I have pulled and pulled and pulled, but have thus far been unable to make the cap budge more than an eighth of an inch, which it was able to do before. Does anyone have a suggestion for how I could get lubrication into the cap without destroying it? If not, I suppose it might be time for new caps and wires. 

Thank you for your advice in advance, and sorry if I rambled on a bit much.

A mate had the same problem and ended up breaking the porcelain end of the plug off. He ended up with a non OEM set with NGK resistor caps. You need to be able to get a good quality penetrant [Not WD40] into the cap which is not easy. You could try carefully  heating and bending the small tube that normally comes with the penetrant and using that to get the penetrant into the cap. You need to let it soak for a few days while reapplying penetrant. A set of vice grips applied to the tab on the cap might then pull it free. Even the plastic NGK caps can be hard to remove. I made up a heavy wire hook which makes it easier and allow me to pull the cap a lot straighter. On the road I have resorted to a piece of Para Cord around the cap to get a better purchase.
Regards Martin.

For really stuck ones I use a piece of wood on the valve cover to pry on one of these with Vise-Grips.

Corrosion often builds up in there over time what you're finding is not unique.

The original caps have a metal tab on them and I have always used a vise grip clamped onto them to get them off.

Probably worth treating the K to a new set of leads and caps.

At Uni I had an old Ford XP 1965 ... gloriously unroadworthy.
One day I had cause to get roadside assistance and directed him to a spark plug that refused to come out (there were 5 others working fine)

Anyway he monstered it with plenty of leverage and out it came. Then he said: "a quite jerk is better than a long steady pull".

Lesson learned

I hope I'm wrong, but Realm Engineering's new website doesn't seem to be advertising K100 HT leads any more. For JohnA:

https://www.euromotoelectrics.com/category-s/1783.htm

You may also be in slightly more trouble than it first seems. If you've got copper carbonate (green stuff) in the plug caps then the leads are pretty much toast as it indicates that the insides of the caps are corroding away. They may be recoverable, but experience says it's not worth the hassle. Also: DON'T lose those screw terminals because most spark plugs come without them these days. If any are shot:

https://www.ebay.com/itm/4-PACK-NGK-Spark-Plug-Terminal-Nut-145-48-NEW-Motorcycle-ATV-Screws-Onto-Studs/201116647222?hash=item2ed37c7f36:g:0NQAAOSws65TrAvY

Mind you, that looks a bit expensive to me and it was the cheapest listing. I got 25 of them in the UK for the equivalent of about $10 including shipping.

Magnecor makes aftermarket spark plug leads for Ks in three flavors. (7, 8 and 8.5) I run them on most of my Ks.

https://www.magnecor.com/

Dai wrote:I hope I'm wrong, but Realm Engineering's new website doesn't seem to be advertising K100 HT leads any more. For JohnA:

https://www.euromotoelectrics.com/category-s/1783.htm

You may also be in slightly more trouble than it first seems. If you've got copper carbonate (green stuff) in the plug caps then the leads are pretty much toast as it indicates that the insides of the caps are corroding away. They may be recoverable, but experience says it's not worth the hassle. Also: DON'T lose those screw terminals because most spark plugs come without them these days. If any are shot:

https://www.ebay.com/itm/4-PACK-NGK-Spark-Plug-Terminal-Nut-145-48-NEW-Motorcycle-ATV-Screws-Onto-Studs/201116647222?hash=item2ed37c7f36:g:0NQAAOSws65TrAvY

Mind you, that looks a bit expensive to me and it was the cheapest listing. I got 25 of them in the UK for the equivalent of about $10 including shipping.

Or, as I found...buy Bosch plugs.....they don't need them.

Dai wrote:I hope I'm wrong, but Realm Engineering's new website doesn't seem to be advertising K100 HT leads any more. For JohnA:

https://www.euromotoelectrics.com/category-s/1783.htm

You may also be in slightly more trouble than it first seems. If you've got copper carbonate (green stuff) in the plug caps then the leads are pretty much toast as it indicates that the insides of the caps are corroding away. They may be recoverable, but experience says it's not worth the hassle. Also: DON'T lose those screw terminals because most spark plugs come without them these days. If any are shot:

https://www.ebay.com/itm/4-PACK-NGK-Spark-Plug-Terminal-Nut-145-48-NEW-Motorcycle-ATV-Screws-Onto-Studs/201116647222?hash=item2ed37c7f36:g:0NQAAOSws65TrAvY

Mind you, that looks a bit expensive to me and it was the cheapest listing. I got 25 of them in the UK for the equivalent of about $10 including shipping.

Looking back at the plugs I pulled, 2 of the 3 of them have copper carbonate on them. The third has no corrosion of any kind on it. At this point, I am going to give the cap another bout of yanking and pulling before giving up on it. After that, I believe I will have to throw in the towel and get the NGK caps and wires. I can't seem to find anywhere that sells the original BMW caps and wires which I would have liked to had, but I am guessing the NGK's will be better than 35 year old caps and wires.

I like the Magnecors so you can color match.

7mm - black
8mm - blue
8.5mm - red

John A wrote: I can't seem to find anywhere that sells the original BMW caps and wires which I would have liked to had . . .

You can still have the original-style at $68 and change per each cylinder's wire assembly , if you are unwilling to accept substitutes. Beru supplies them. Check the Max BMW parts fiche in the Engine Electrics section and click on the Ignition diagram.

Try heating that cap with a hair dryer a little before jerking it from its nest on the plug's terminal nut. A long, grunting, dying strain on the cap usually won't free it.

This morning I went out to the bike with the resolve to pull the cap or rip the tab off in trying. This time instead of pliers, I used a pair of vise grips. I was able to pull it free. Somehow a rusty staple was responsible for binding the whole thing up. This plug, much like the second plug I pulled had no corrosion on it. I have no idea how a staple managed to find its way in there though. I will be taking the bike out once it dries up around here to make sure everything is in working order. Thank you for the help. I will probably still replace the caps and wires at this rate, but the replacements will stay on the shelf until I notice a problem most likely.

Once again, thank you for the helpfull ideas and the links to the parts.

I have a set of brand new NGK plug wires in my spares inventory.  Amazon has them for $70, I'll let you have them for $45.

I am just down the road from you and can bring them to you next week.  If that doesn't work I can post them today If you give me your address.

Point-Seven-five wrote:I have a set of brand new NGK plug wires in my spares inventory.  Amazon has them for $70, I'll let you have them for $45.

I am just down the road from you and can bring them to you next week.  If that doesn't work I can post them today If you give me your address.

PM sent, thank you.

When using the OEM leads it is also important to get them firmly seated on the plugs when installing.  I grab the tang on the OEM spark plug lead with the pliers from the OEM toolkit and then smack them with my free hand to make sure the cap goes all of the way onto the plug.

PM reply sent.