I'm just starting to tool around with my 'New to Me' 74 Ironhead. It's myt first Harley and yes everyone has told me I am over my head, but how else am I to learn? Anyway, I was curious what Brand and model spark everyone is using. The guy at Autozone tried to give me a lawnmower plug that had a different length and thread. Keep in mind, I'm in Texas were the wind in your face feels like a hair dryer this time of year. Lol

 

Spark Plugs for
Sportster Engines

Sportster 72-79

Plug Gap 040"

H-D Standard 4-5
H-D Gold 4R5G
Champion H8C
Autolite 996
ACCEL 2402
Splitfire SF21F
Screamin Eagle XL10S
Denso Iridium IWF22

Any of these will work for your 74 ironhead.

 

Have you found any of these to be better than the others?

 

I have tried them all with NO noticable difference. I just stick with whats on sale and pick up a few at a time.

 

I use the Champ H8C. It was listed as the stock option. Average price with average life. Until you go high preformance don't over think the plugs. Just stay close to stock which ever brand you buy. If your piston rings or valve guides are worn the plugs won't be in there long enough to matter.

 

I always use the standard Harley plugs that the FACTORY SERVICE MANUAL recommends (not the Clymer books... they have lots of incorrect info in them). Champion makes the HD plugs to Harley's specs for each particular model engine. They each have a heat range that isn't available at any auto parts store, although the substitutes mentioned above are somewhat close. The others can be used, but aren't really the "correct" ones. Don't waste money on the fancy HD Gold, Platinum, Splitfires, etc. They are just designed to drain your wallet and perform no better than the stock plugs. That's my 2 cents....

Oh yeah.... NEVER change to a "hotter" or "colder" plug to compensate for poor performance or fouling. You are just covering up the real problem. ALWAYS use the plugs recommended by Harley. If they are fouling, then you need to rejet the carb or rebuild the top end if they are oil-fouling. Remember, a spark plug's heat range does not mean a hotter or colder spark, it means the rate at which heat is removed from the combustion chamber. The only thing that changes the power of the spark is the coil.

 

Could someone tell me the difference between a Champion h8c and a h10c? I just put new plugs (h8c) in my bike ('73 Ironhead) and noticed that the plugs that were already in there were h10c's.

thanks,
Chris

 

I put 41k of the 52k on my Ironhead's clock. I used the Champion H8C's for a few years. I found that the life was only about 5k or so. I ended up buying a set of the SE Splitfires back when they where hyped up to be the "thing." Now we all no better, but they sure to run good in my Ironhead. I get 10+k on a set before having to change them.

 

I just put Champion RL82YC in my '81 ironhead. I used the following table as a cross reference - http://www.harley-performance.com/ha...park-plug.html

 

I have used several years Champ H8C, now I had in my new project HD #4 plugs I noticed little difference between those
HD plug has longer thread than Champion, only about 0,1"
I don't know if there is any meaning... so

-sepixlh-