1955 FL Spark plugs

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1955fle
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1955 FL Spark plugs

#1

Post by 1955fle » Wed Feb 12, 2020 7:54 pm

I know this has been talked to death, but I always used Autolite 4257 plugs in my 1955 FL. I can not find them anywhere. What should I use instead? Any thoughts?

Carl



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Re: 1955 FL Spark plugs

#2

Post by panhead_kicker » Wed Feb 12, 2020 8:17 pm

Why not use Harley 3-4 plugs?

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Re: 1955 FL Spark plugs

#3

Post by 1950Panhead » Wed Feb 12, 2020 8:22 pm


1955fle
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Re: 1955 FL Spark plugs

#4

Post by 1955fle » Wed Feb 12, 2020 8:32 pm

1950Panhead wrote:
Wed Feb 12, 2020 8:22 pm
Champion j12yc
https://www.ebay.com/sch/i.html?_from=R ... mpion+plug
The champion j12yc is a short reach plug. I have always used Autolite 4257 which is a ling reach plug. Have I been using too wrong length plug?

Carl

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Re: 1955 FL Spark plugs

#5

Post by RooDog » Wed Feb 12, 2020 8:53 pm

The Flathead Ford spec'd plug, Champion H-11, is equivalent to the H-D 3-4 plug. Surely, much like motorcycle oil, or ice cream flavors, there are too many choices to list here, and they are all good in somebody's mind.....
....RooDog....

PS: I use the Bosch Platinum WR9FP in my 1950 74" Panny....

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Re: 1955 FL Spark plugs

#6

Post by RUBONE » Wed Feb 12, 2020 9:37 pm

Standard plugs for all H-D Panheads were 7/16 reach. Aftermarket heads are different.

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Re: 1955 FL Spark plugs

#7

Post by bobberguy » Thu Feb 13, 2020 5:06 am

I just got a four pack of Autolite 4275, not 4257. Amazon $6.50 for four. Good deal. Checked with Autolite tech line and the 4275 are copper core, NON-RESISTOR which is correct for stock Panheads. They work fine in my 56 FLH. This crosses with Champion J12YC.

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Re: 1955 FL Spark plugs

#8

Post by RUBONE » Thu Feb 13, 2020 6:00 am

Here are some old pics of a couple H-D 3-4s and a Champion J12YC, the most current replacement. Champion builds H-D plugs. The 3-4 are extended tip, H-D #4 like used on older Sportsters were H-10s and the recommended plug for high speed use. Champion numbers are lower for hotter as opposed to most other brands.
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DCP_2786.JPG
DCP_2786.JPG (140.29 KiB) Viewed 194 times

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Re: 1955 FL Spark plugs

#9

Post by RUBONE » Thu Feb 13, 2020 6:11 am

A few more old H-d plugs..sorry about the lousy picture....
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Re: 1955 FL Spark plugs

#10

Post by FL54 » Thu Feb 13, 2020 2:49 pm

+1 on the Bosch Platinum plugs. But as Roo says, it’s like asking what oil do you use.

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Re: 1955 FL Spark plugs

#11

Post by RooDog » Thu Feb 13, 2020 2:59 pm

I don't see that a spark plug is a hi-tech, nor critical item, if it works for you in your machine. Only if one is competing for 100 point show judging does it become an issue, and then remove from your gold plated, and well padded carry case a set of genny Harley branded plugs just for the judging, and remove them away for the next time they are called to serve proudly toward earning that highly contested trophy. And pray that you don't get gigged for the wrong oil in the tank, or the wrong clutch fiber discs....
.....RooDog....

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Re: 1955 FL Spark plugs

#12

Post by RooDog » Thu Feb 13, 2020 5:36 pm

Champion J-12Y Spark Plugs: They are on eBay, how many do you want?

https://www.ebay.com/sch/i.html?_from=R ... s&_sacat=0

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Re: 1955 FL Spark plugs

#13

Post by 1955fle » Thu Feb 13, 2020 9:52 pm

RooDog wrote:
Thu Feb 13, 2020 5:36 pm
Champion J-12Y Spark Plugs: They are on eBay, how many do you want?

https://www.ebay.com/sch/i.html?_from=R ... s&_sacat=0
I bought some J12YC plugs and will happily use them. Thanks for all of the replies.

Carl

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Re: 1955 FL Spark plugs

#14

Post by Andygears » Fri Feb 14, 2020 12:17 am

1955fle wrote:
Wed Feb 12, 2020 8:32 pm
1950Panhead wrote:
Wed Feb 12, 2020 8:22 pm
Champion j12yc
https://www.ebay.com/sch/i.html?_from=R ... mpion+plug
The champion j12yc is a short reach plug. I have always used Autolite 4257 which is a ling reach plug. Have I been using too wrong length plug?

Carl
There have been Shovelheads bought for cheap, running badly, that the “New Plugs” were short reach when long reach were required. Kinda important.

Andygears

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Re: 1955 FL Spark plugs

#15

Post by panhead_kicker » Fri Feb 14, 2020 1:04 am

panhead_kicker wrote:
Wed Feb 12, 2020 8:17 pm
Why not use Harley 3-4 plugs?
https://www.ebay.com/itm/24-New-OEM-Har ... 6123!US!-1

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