1986 XJ700 Maxim-XS...Spark Plug Arcing

Just posted my intro last night http://xjbikes.com/Forums/viewtopic/t=12660.html in the GL so I wont blather on.

I have been hearing a ticking or clicking sound in the vicinity of the left side cylinders which my neighbor (who is an electrical engineer) thought was arcing. Started the bike up at night and sure enough blue flashes of light were bouncing around from plugs 1 and 2 (fairly new D8EA). 3 and 4 were OK. When you give it gas though the arcing stops? From what I am reading it sounds like the plug caps or wires but how can I be sure? They still look new (only 3900 miles on the bike). The bike starts beautifully with a half twist of choke but I have to leave it on at least a quarter until warm or it will crap out. Once warm steady idle right at 1k. And the bike is a rocket in all gears and revs except 1k-3k in 1st.

Let me know if you need more info. Also, probably a stupid question but in the short term if I continue to ride with this condition am I doing further damage to something else down stream? Thanks in advance...

 

Plug caps screw into the wire - check if they have gotten loose. You can just tighten them. If they are worn at the end you can cut them back a bit (1/2 inch or less) if you have enough extra length. Look for splits in your wires and cracks in the caps while you are at it.

Arcing will rob power from your spark making a weaker spark so I can/will effect how your bike runs.

The choke sounds about right for a cold engine. Search on plug chop in the forums. The plugs really tell the tale of how well tuned you are.

 

I'm sure you saw it from my thread, but I've had this exact same issue with my XJ700X. The arcing seems to occur at the hard section of the plug boot (right above the orange rubber section). It will arc onto the valve cover and I've currently only seen it happen on cylinders 1 and 4. I also remember it only happening when my bike was idling REALLY low and about to bog down and die, otherwise, everything was fine. I haven't checked it after I got the bike running much smoother and can't really go back and check it now since I messed up my carbs, but just chiming in to say you're not alone and I'm subscribing to this thread for potential solutions.

 

Thanks Bill. I would never have known the plug cap just screws into the wire like that. They weren't loose but since I had #1 unscrewed I took #2 off and screwed them both back tight. Inspected caps and wire back to the coil and they look great...no cracks, splits etc. at all. Fired the bike back up and still arcing at 1 and 2. I have newer NGK D8EA's in there per HAP"S recommendation on maxim-x.com, which I quote:

"If your Maxim-X still has the stock coils and you're uncertain about the condition of the rest of the ignition system, then err on the side of caution by installing non-resistor NGK D8EA spark plugs as Yamaha did in 1985, or use an equivalent D8EA substitute. It'll improve your odds of getting the bike on the road without too much cost and effort... albeit slightly"

Yamaha supposedly changed the spec to include resistor type spark plugs for the 86x vs non-resistor for the 85x. Just wondering if this has been tested to any degree with the X nation here and could the higher heat rating in the resistor plugs be a factor in the why there is arcing. If the coils were going bad could this be the culprit? (again very low mileage bike). Would a pull of the plugs provide any info to help solve this issue?

Wombat, I am following your thread closely...its all good!

 

Unscrew the Plug Cap and try adding a layer of Industrial Heat Shrink to the Plug Wire.

 

Rick, could you expound just a little? Not sure what you mean

 

I remember having this problem and never took care of it. If my bike runs great now this will make it better. I also never knew about the caps screwing on. I'll check it now. Great questions. Even better answers!

 

I have not researched this on this forum, but has anyone used dialectric grease on your caps? I think the reading on the tube states that the grease will help with this.

 

The Grease won't help too much if the Cap has a fracture on it. Look at the Cap under a magnifying glass ... from all angles ... see if it's got any hairline fractures in the composite. If you find a crack on it; the best thing too do is replace it.

 

Lacking any cracks, dielectric grease is a good idea to promote ease of cap removal and to ward off water intrusion. Just a smear, not gobs. The silicone grease is very good lube for the boots and helps protect them against cracking and hardening.

 

Just an update...

I removed the plug caps and inspected carefully along with the wires. No cuts, cracks or damage at all. Decided to take Bill's advice and so cut a 1/4" off the wire ends for a fresh bite and then smeared some dielectric grease on the spark plug's ceramic body and metal screw cap along with some on the inside of the plug cap boot. Reassembled everything tight but no change...still arcing about the same. I happen to notice when I had everything off that the plug and cap connection is not a true male/female kind of deal. They basically just butt up to each other. However, when you unscrew the metal cap from the spark-plug the smaller threaded end can now slip inside the metal connector in the plug cap (a little). Does this matter? Plugs 3 and 4 don't have any arcing and are installed with the screw on caps. Any thoughts?

Am looking into this idea Rick threw out there about heat shield too. Thanks much...

 

nice look'en bike there
just do it right and hit Chacal up for some spark plug caps and plug wire splices or search for "new plug wires" by Mr. 'omatic, i believe
time just gets to that rubber stuff and fixes won't last long, you want new on a bike like that

 

From what I've read here, some caps use the metal bushing on top some use the threaded post without the bushing.
My caps actually click down onto the metal bushing.
I don't think it should be a butted against each other situation.

Are you using the recomended plug type.
It seems to me that the difference between using metal bushing or threaded post was if your bike used resistor plugs or not.
Some bikes the resistance was built into the wires and after market wires did not have the resistance.
Some one jump in and help me explain this if what I've said is wrong.
This just maybe his arcing issue.
If the plug wire and plug are being vibrated apart constantly it could arc.

 

Ahhhhhh...here's what I've been looking for http://xjbikes.com/Forums/viewtopic/t=8 ... plice.html scroll down that link to read Chacal's entire post but to paraphrase:

"Spark PLUGS on all XJ-series bike were factory NGK models. Although many other brands of plus can be safely cross-referenced to the originals, NGK plugs offer both a value and performance that is quite satisfactory, in both original design configurations or high-performance "Iridium" design plugs. All non-resistor plugs have a resistance equal to zero ohms, while all resistor plugs.....those with an "R" in their part number.....have a resistance rating of 5K ohms. NOTE: all original and replacement plug caps are designed to be used on plugs that have their screw-on insulator stud cap removed, and used with the threaded stud exposed. And the NGK plug caps are specific to either the 12mm plugs (all XJ550's and all XJ700-X models) or the 14mm plugs (all XJ650, XJ700 non-X, 750, 900, and 1100 models)".

"In conclusion: you can safely use replacement NGK plug caps with a 5K resistance rating with either resistor or non-resistor type spark plugs. If replacing spark plug wires on either original coils, or when using aftermarket coils, it is recommended that you use copper core, non-resistance spark plug wire. Doing the above will give you the total 5-10K plug/cap resistance values that coils need to "see" to perform properly. And finally, always check, with an ohm meter, your coils primary and secondary resistance, and your plug cap resistance, before you start "throwing money" at engine performance problems that seem to be electrically-related"!

Guess I will try removing those screw on caps from the plugs and see what happens. Still wondering about the issue of of using non-resistor plugs which were spec for the 1985 Max-X versus resistor plugs which were spec for the 1986 Max-X. Sounds like they are both "safe" but has anyone tested one against the other in terms of performance?

 

I removed those threaded bushings from the spark plugs and now those two plugs are arcing worse. Its like a fireworks show at night. If a more solid connection makes it worse would this now indicate that the plug caps are probably bad even though they look perfect? Would an ohm meter reading on the wires and/or plug caps be the next logical step? Or is that not even relevant to the problem of arcing? This stuff is totally new to me...thanks much.

 

Can you tell where it is arcing from? Wires or caps? What Rick was suggesting in putting some high temp heat shrink on will insulate over any cracks. You said it sparked worse after you took the barrels off. I'm wondering if the barrels opened the connector and you have a loose fit.

I don't think those caps are expensive (I have never had to buy any so I don't know) you may want to replace them and give that a shot.

 

you could try using spark plug boot grease,it is supposeed to prevent arching.

 

It seems to be coming from the orange insulator boots right at the base of the opening to the plug hole. I tried to search for this heat shrink stuff but not exactly sure what it is. Would an Auto Zone type place sell this? I did put a little di-electric grease on the threaded plug tips, ceramic body and a dab on the metal connector inside the plug boot. I dont mind buying new plug caps but just want to trouble shoot in an orderly manner. Thanks again!

 

Radio shack has heat shrink tubing- may not be a thick as the stuff Rick is talking about but would do to test. But I don't think that is your problem.

So if I follow you the arc is from the "bottom" of the boot to the case going around the plug so to speak? If that's right I would think connection to the plug. Electricity is always going to take the path of least resistance which should be your plugs in this case not arcing to the engine.

Can you tighten the connector inside the boot? I would say it's that or the boot is just bad and needs replacing. The other advice you have been getting is because it is far more common to have arcing from the wires or wires/boot junction.

 

If you have an owners manual it will tell you the resistance for the coils and how to test them new caps are $6-10 at any bike shop will likely fix your problem and is the cheapest place to start