1986 XJ700 Maxim-XS...Spark Plug Arcing

I am waiting as we speak for the XJCD's. Just wasnt sure if the ohm readings would be of any help to solving this problem. The bike really runs pretty well otherwise

I think thats right Bill. Its hard to know whats going on because you cant see past the orange insulator boot but it seems like the spark is leaking past the boot and onto the case. Not sure how I would tighten that connector as its the taller Tokai Denso caps and its buried pretty deep. Does that connector inside the cap screw into something or is it welded? One last thing...I noticed the two arcing plugs look really lean (white). Sounds like this related to mixtures but just throwing it out there in case its relevant. Appreciate all the help.

 

You can also remove the caps and check there resistance i know i had to replace one of mine because it was nfg

 

Bringing this thread back up. I've replaced a good amount of seals and o-rings to try and get my bike to idle correctly, but it just isn't listening. After a nighttime ride, I noticed that my plug caps are still arcing like crazy, but it will only happen at idle (and when my bike dips below idle.

I haven't tried to solve the arcing problem...yet, but I'm beginning to run out of ideas as to why my bike won't behave at idle.

 

OK...so I took all the plug caps off to check resistance

#1 8,800
#2 9,900
#3 9,900
#4 8,900

Pretty consistent numbers and within spec I believe. Here's my new problem. Out of morbid curiosity I disassembled #1 to see what the guts looked like. There was some corrosion on the top (wire side) of the spring which I wire brushed off. Also rubbed the tiny brass disc against some fine sandpaper. Put it all back together and now cannot get ANY resistance reading? The resistor reads fine outside of the cap and also with the guts aligned on a work bench but once I put everything back in the cap -- nothing!

Is it possible that the corrosion on the bottom of the spring was acting as a bridge to allow some conduction? If that top plate (or whatever it is that completes the connection to the wire lead) where the spring rests is corroded could it be cleaned with a long Q-tip and solvent?

I know, I know -- just buy new caps and be done with it. To be honest, this is a lot more about learning about my bike than the $20 for new caps.

 

Don't be alarmed, this happened to me as well and I disassembled and reassembled the plug cap about 50 times before I got a reading. Even when I got a reading, it was WAY out of spec (like 1200K Ohms). I tested the plug cap for spark on the bike and it was fine, so I shrugged my shoulders and put it on anyway and the bike ran great. I retested the spark plug caps after a couple hundred miles of riding and I was finally able to get them to read properly again. I'm thinking the vibrations from the engine allowed the internals to settle back into place.

Anyway, take a look at this thread: http://xjbikes.com/Forums/viewtopic/t=2 ... +caps.html

We're not alone and that thread has some links to some really nice spark plug cap replacements which are dirt cheap! I think I might order a set just to have them around in case anything happens. Seems like cheap insurance to me.

 

Great stuff...thanks again Wombat! I honestly thought I was losing my mind after re-assembling the thing like 10 times w/grease...without...etc. Guess I will proceed with taking them all apart, reinstall and see where I stand. Good idea on the insurance policy too...would be interesting to compare those NGK 5k caps against the stock 10k in terms of performance.

 

SPARK PLUG CAPS ARC FOR 1 OF 3 REASONS ONLY

1. BAD/CORRODED/NON EXISTANT CONNECTION AT THE PLUGWIRE-METAL CONNECTOR JUNCTION INSIDE THE PLUG BOOT

2. SPARK PLUGS ARE WRONG TYPE , OR HAVE EXCESSIVE GAP AND CANT FIRE

3. PLUG WIRES OR BOOTS ARE DEGRADED

IF # 3 IS THE CASE, YOU CAN SPLICE NEW WIRES ONTO THE OLD (WAY UP NEAR THE START OF THE WIRE IS BEST) USING NGK'S PLUG WIRE SPLICER


* I SUPPOSE THAT THEIR COULD BE A POSSIBLE SCENARIO WHERE SOME CHECMIAL WAS USED ON THE BIKE ( TO WASH OR CLEAN OR SOMETHING ) AND THAT CHEMICAL IS ELECTRICALLY CONDUCTIVE AND HAS GOTTEN DOWN IN BETWEEN THE BOOT AND THE WIRE...ALLOWING SPARK TO SEEK EASIEST PATH TO GROUND.

 

"Path to Ground" says it!

There has to be some Path to Ground.
It might be a hairline fracture too small to see with the naked eye.
Try looking at the Plug Caps with a magnifying glass and see if you can detect a hairline fracture.

If you KNOW the Plug Caps are arcing, anyway ... tape 'em up and see if that ends it.
If it does ... get yourself some new Plug Caps!