Best Spark Plug for a 1937 UL

[Wade]

While I'm getting new spark plugs for my 1937 UL HD I thought I would see first if anyone here has a favorite that would fit that engine?
I love a kick start, but I'm not fond of having to crank it over and over while a crowd gathers out of curiosity and inevitably for amusement. If you have a suggestion for a favorite spark plug that would work for a 1937 UL I would sure like to hear it.

Thanks for any opinions/insight.

- Wade

[RichO]

plugs

Either original air cooled HD #3's or the suitable sub, champion D-16's. They're 18 mm and fit Super X, 101 Scout's, and Knuckles and flatties.

[Rollo]

plugs for 37UL

I have been using Champion D-16 or D-14 plugs for over 30 years in my knuckles and flatty's and no problems. I have original #2 and #3 plugs but try to save them since they are so expensive now. I have VL's from 33-36 and knuckles from 41-47 and they work fine and you can get them at most auto supply shops or tractor supply shops.

Rollo
AMCA #12766

[rousseau]

NGK A-6
Got mine from "Bullwinkles cycle" (502) 223-7688

[Jerry Wieland]

C-86 AC or 386 Autolite at the parts house. Refuse to run Champion in anything but thats another story.

Jerry

[Wade]

Thanks

Thanks for the help! - Wade

[ronald]

check out your local NAPA store for the D-14 or D-16 Champs. I've been using them for a number of years. At $2.29 ea in a box of 6 they won't tear up your wallet.
Ron

[joel58pan]

Are the Champion D-14 and D-16 the same heat range as the H-D #2 and #3, respectively? What heat range (plug) would a 45ci with #5 heads want for a plug?

[T. Cotten]

Folks,

Beware that modern productions of NGK A-6 plugs are resistors, and will foul with conventional ignitions.

(NGK's tech support denied it, but my vendor discovered that they were made to accommodate modern Wisconsin motors.)

A simple test with a common ohmmeter will detect the modern from NOS.
Older plugs have a knurl, and a thicker hex as well.

....Cotten