1957 G model

Spark plug recommendation

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lpd1snipe
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1957 G model

#1

Post by lpd1snipe »

I recently bought a Servicar from a friends family who owned it since 1992. He's no longer with us to ask. HD recommends #3-4? Any good recommendations on spark plugs or a cross reference? It has Champion RJ12YC in it currently. Thanks guys.
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Re: 1957 G model

#2

Post by RUBONE »

lpd1snipe wrote: Sat Nov 05, 2022 1:36 pm I recently bought a Servicar from a friends family who owned it since 1992. He's no longer with us to ask. HD recommends #3-4? Any good recommendations on spark plugs or a cross reference? It has Champion RJ12YC in it currently. Thanks guys.
A Champion J12YC is the equivalent of a 3-4 HD plug, in fact they make them for H-D. But avoid the R prefix, that is a resistor plug for electronic ignitions and makes it harder on the system to fire consistently well. Do not use resistor plug wires either.
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Re: 1957 G model

#3

Post by lpd1snipe »

Thank you
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Re: 1957 G model

#4

Post by Pascal »

Champion D14 or D16 is fine too...or NGK A9's
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Re: 1957 G model

#5

Post by RUBONE »

Pascal wrote: Sun Nov 06, 2022 8:00 pm Champion D14 or D16 is fine too...or NGK A9's
Champion D14, D16, and NGK A9s are all 18 mm. A 57G with stock heads is 14mm plug size.
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Re: 1957 G model

#6

Post by kitabel »

A9 is not only the older & larger thread, but extremely cold and not suitable for street use.
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Re: 1957 G model

#7

Post by Pascal »

RUBONE wrote: Sun Nov 06, 2022 11:49 pm
Champion D14, D16, and NGK A9s are all 18 mm. A 57G with stock heads is 14mm plug size.
Yeah...I realized that some time later too..thanx
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