Plug heat range

[kell]

The plugs have been fouling on my pan (1952, stock displacement, STD heads). S&S super E with 0.070 main and 0.0295 intermediate. Mufflers. I went from RC9YC to RC12YC already. I guess I will have to go to something hotter, but I was wondering: there must be some kind of tradeoff, is there a disadvantage to running hot plugs?

[Ente]

Hi Kell.
Because of the longer isolation-nose in the hotter plugs they schould not be used in performance-engines because of the bad heat-transfer and it could self-glow and produce extra detonation, but they are perfekt in standard engines and a recomendation. And a cold plug in a standard engine will not burn away all carbon, which results in bad mileage and sparks. But are necessary in a performance engine to stand the heat...
So I guess the answer is: NO disadvantage in standard-engines....

[Cotten]

Kell!

You have an electronic ignition?
If not, trash those resistor plugs immediately, and resistor wires, if you have them, as well. (Accell yellow crap are the worst I've encountered.)
If you still foul on a points ignition, tell us if it is a wet carbon or dry sootiness on the plugs, and if the plugs are different in color.
(Post modified to get rid of an annoying emoticon.)

[Ente]

Hi Kell..
Just went so excited about the heat-range and answer THAT question. Smile As an advice about the fouling... Listen to Cotten..

[kell]

Cotten:
I have an electronic ignition. No computer, though. It is homemade. I put hall sensors on the stock manual-advance breaker plate and mounted stationary permanent magnets above them, with a shutter wheel attached to a bushing I mounted on the shaft, for shunting the magnetic field, during dwell. The sensors trigger transistors (regular ignition IGBT's) that I put in the space under the plate. I am already running solid copper plug wires with no ill effects, and will look for non-resistor plugs. I don't anticipate any problems, the circuitry is not temperamental and I have bypass capacitors for the sensors and transistors (to absorb the transients that come back from the coils, which a lot of people misidentify as "RF interference"). It's single fire and I run 1.2 ohm coils off a ballast resistor about 2 ohms.
The fouling is dry soot. Today I switched to a 028 intermediate jet, rode a hour or two but still too early to tell if it will foul up again. If it does I will maybe try a 68 main. Also going to look for c12yc or c14yc (without the "r") or equivalent, as per your suggestion. Although the Champion web site didn't have them. It's c not j because they are the plugs with 5/8" hex head and the long threads (the bike has STD heads) so I suppose there is not as much variety.
Oh there are four plugs, all look the same.

[Cotten]

Wow! You went way over my head! (I'm still lost in the first half of the 20th century.)
All four plugs burning the same is a good thing of course. With a little patience I'm sure you will dial her in perfect.

[Ente]

Hi Kell.
Could it be the accelerator-pump that pump in to much fuel? I run my with S&S super B with 0.074 main and 0.031 intermediate. 2-1 pretty open exhaust. RC12YC-plugs. Points with one Andrews-coil, 1 plug/cyl. And my plugs are brown

[weezeo]

Don't know squat bout all that electro thing but minus the heads (STD) I run the same carb with A grind and use J12yc or J13Yc and they do work well but I have been known to gas foul real cold start lke whern its beeen raining for a month. use 68 or 70 main

[ironman]

I have been running autolites for about 15 years and they seem to run better and longer than the champions do, they might solve your problem. The 75 is the same as a J12YC, the next hotter plug is a 76. If you need resister plugs they are 85's or 86's.

[Ente]

ironman..
Are they still making the Autolite? Here in Sweden it was years since I saw them in the shops, but I will look after them now. I'm very pleased with the Champions.. but.... you will never stop sorted and testing things out Smile

[kell]

Trying to find plugs that correspond to the RC12YC but are non-resistor. Champion doesn't list C12YC, so I have nothing to cross-reference. Can't use J12YC, these heads take a different size plug.

[panhandler]

I am running the longer plugs in my heads and ran the Champion N11YC with an S&S E, andrew J and 29.5/68-70 jetting. I have switched to Autolites cross reference to the Champion and they run fine. I run dual crossover exhaust with fishtail mufflers. The autolites are cheaper, I get four in a package for the price of two Champions. If you are interested in the number of the autolite, let me know and I'll run down to the shop. Regards....... Smile

[kell]

Next time you get a chance. It would be good to know the number so I can try them.

[panhandler]

Kell, they are Autolite #64. I don't know what you're running for pipes, but Ente touched on a point with the accelerator pump setting. I have mine turned out 1.5 turns. As Cotten suggested you may have to play with the dials for a while but I have found the best way is to let the bike warm up for about 3 minutes just until the pan covers are warm and shut my pump off, then dial my enrichener screw lean (clockwise) until she starts to die and then rich (counter) til the same thing happens. Then dial her back about halfway between these two points and you should be in the ball park. Hope this helps, good luck......Panhandler

[57stroker]

Try this plug: http://www.ngksparkplugs.com/ I was told by some old-timers that NGK developed this plug just for the short reach Harley motors. I have to order them from NAPA, but sure like 'em. They seem to take longer to warm up like most NGKs, but they run good and last a long time.