Spark plug choices

I have been looking at upgrading my spark plugs for my XS2 , I know everyone has their preferences.

My ignition system is a Pamco, with a high output coil, new solid core silicone wires, and new NGK resistor plug caps.

Presently I’m running standard NGK BP7ES plugs

I have been looking at NGK Iridiums BPR7IEX,
Really nice plugs, if expensive.

Also, Autolite AP63 , platinum core , very reasonably priced. XS Leo runs these.

Anyone running any other brand of platinum or iridium plugs? Bosch or Nippondenso perhaps?
Got any hot tips on good prices?

Hey, Bob.
Lots of endorsements in here for AP63s.
Economical, reliable, available.
Besides, these will be your "break-in" plugs, tossed at the 500 mile tuneup.

I'm running the BPR7EIX, with no-resistor caps.
Quite happy with them.

More fun reads:

http://www.xs650.com/threads/e3-spark-plugs.36815/

http://www.xs650.com/threads/nkg-iridium-spark-plugs-bpr7eix.48251/

http://www.xs650.com/threads/indexing-spark-plugs.48354/

TwoManyXS1Bs said:

Hey, Bob.
Lots of endorsements in here for AP63s.
Economical, reliable, available.
Besides, these will be your "break-in" plugs, tossed at the 500 mile tuneup.

I'm running the BPR7EIX, with no-resistor caps.
Quite happy with them.

Another fun read:

http://www.xs650.com/threads/e3-spark-plugs.36815/

Click to expand...

Thanks Steve! I never really looked for alternatives before tonight. I was surprised that there are quite a few options.
I’m running the NGK Iridiums on my ‘77.

My situation is a bit different. Old man kick-start only.

Hot weather, cold weather, hot engine, cold engine, first start, after an hours stop, right after the traffic light chug/stop blooper, winter blend, summer blend, any of those combos, ...etc.

The BPR7EIX plugs have given me the least grief, almost always a 1-kick start.

Of course, they're indexed...

Clocking plugs....there's a nugget a lot of folks never consider.

A dual output coil such as used on the XS650 produces a negative voltage for one spark plug and a positive for the other. The magic of Iridium spark plugs is the ability of the tip to get very hot without self destructing. This hot tip then acts to promote the emission of electrons from the negative spark plug tip towards the grounded electrode, much like the way the cathode worked on tubes for those of you old enough to know what tubes in TV's were. However, the hotter tip has zero effect on the positive voltage on the other spark plug, so Iridium's are a waste of money for one of the cylinders, but figuring out which is which is tricky, but if you could figure out which is the negative spark plug wire, you would benefit by installing an Iridium just on the negative spark plug wire and save the cost of a useless Iridium on the positive wire.
Some auto manufacturers who use a dual output coil mitigate this issue by installing a different spark plug on the negative cylinders vs the positive cylinders.
There are a couple of methods to figure out which is the negative wire and I will share those methods with you if asked, which will also serve to let me know if anybody is actually reading this post.

I thought this would be a quick little read to get some info on plugs. Over an hour later I've finished 2M's links. Think I'll just grab whatever cheap as plug I can find, side gap, index, done. Thanks again guys!

pamcopete said:

There are a couple of methods to figure out which is the negative wire

Click to expand...

I'm interested.

Yeah, I think this is interesting also. I don’t know as though I’d run two different kinds of plugs at the same time but the science behind it is interesting.

Tom Wesenberg Tip:
"To check coil polarity hold a pencil lead in the spark path with the plug wire about a third of an inch away from the distributor terminal. You’ll see a FLARE on one side of the pencil lead and this flare should be on the spark plug side of the lead." Tom suggests to hold the pencil in the middle or even slide the pencil into a plastic tube to avoid an electrical shock.

I was going to mention how to check the polarity check but while I was writing out my post gggGary posted it first. I went back and edited my post to remove my poor explanation to let gggGary's much better one stand alone.
I thought once of getting two separate coils with the right input ohms then wiring them in series to get proper ohm reading Might have to add a resistor, then wiring them both to the right polarity. Then using the iridium plugs may be worth the extra cost. I tried the Iridium plugs. They cost about $7 each then, probably more now. I tried the AP63's and the bike ran just as well with them. They cost about $4 a pair then. They more costly plug for the performance gains was not cost effective. No noticeable gain but costing about 3.5 times more. You do the math.
The AP63 has the center pin of platinum. kinda like the Iridium plug has a Iridium center pin. So would probably work better with both plugs have the same polarity.
I also run a Pamco ignition. It came with the green monster coil so that's what I run. I upgraded by adding the E-Advancer. Works great by the way. well worth the cost. I know the green monster coil can be a problem, but it is working good for now. I try not to leave plug wires unhooked, that's where the trouble starts.
On my 83 I put in the kit that came with the E-Advancer. I used the stock coil and it's working fine. My next Pamco will be the one with the E-Advancer built on the sensor plate. Clean up the install. My 82 is acting like the TCI is crapping out.
Leo

I ordered a box of four AP63’s for $9.95 and free delivery on eBay, just moments ago. Such a deal!

Still working my way through a box of "used once" standard NGK BP7ES plugs that came with an oil burning TX750, torch, brush off the ash, install. After 10's of thousands of XS650 miles don't think I've ever replaced a worn out plug. I have used a BP6ES or two as a band aid on a cylinder using oil... I've removed a lot of different plugs from "used to run" XS650's that arrived here, a few had NO resemblance to the right plugs.

To really get old spark plugs clean, never mind the sand blaster, brushes etc. Just soak them in battery acid for a couple of hours.

The guys who are running high output coils should think about increasing the plug gap. The higher voltage will jump a larger gap. The longer spark has a more consistent firing of the mixture.

As well as needing less energy, Iridium plugs don't shroud the mixture as much as a conventional electrode. There is less flame quench due to less mass. The initial flame kernel is larger. All minor but good qualities.

Denso has a plug with a tiny .4mm electrode. I run one in my high compression SR 540.

Tom

My vote is for the Iridium plugs. I've been running them with the 'Kung Fu' coil that both MMM and the place in Florida sell. Modern high-performance wires and no-resistor caps. I was able to hit a .060" gap without it breaking up on top, chickened out above that. But, do your tuning with regular plugs, that combo will light off just about any mixture and doesn't give you enough feedback on jets. Feels real good to drive it.

Do you really need resistor plugs or caps? Is the only reason for them to not interfere with someone's antique AM radio?

xjwmx said:

Do you really need resistor plugs or caps? Is the only reason for them to not interfere with someone's antique AM radio?

Click to expand...

Modern electronic ignitions produce a very high Voltage to the spark plugs. After the initial spark across the spark plug gap, it's important to reduce the current that actually flows during the spark to reduce the current through the tip of the spark plug to reduce the erosion of the tip. That is one of the functions of the resistance in the spark plug or the spark plug resistive cap.
Not only is it important to reduce interference to old AM radios, but the spark plug also creates interference to the electronic ignition itself that needs to be reduced to avoid misfiring. The very high Voltage works by jumping the gap, which can be increased to take advantage of the very high voltage, but once the spark has jumped the gap, it is no longer needed, so the resistance serves to just limit the current.

Excellent answer Pete, I remembered hearing that it somehow could affect the ignition system but I have never heard it explained clearly.

OK So mine still has points but uses the Dyna coils. Why would it need resistor ANYTHING in the secondary side?