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Best spark plug reccomendation for UL.

Moderators: Curt!, Pa

Post Thu Jan 16, 2014 8:10 pm

Posts: 470
Location: Six miles East of Cheney, Wa.
Does anyone have a really favorite spark plug (big threads) for a fresh, stock UL engine? I used some plugs I had laying around, (Champions, recent manufacture, probably for a knucklehead) and I've fouled out the rear one already. However...running the engine very rich, before I accepted just how lean I had to adjust that Bendix to run right, probably did not help. Anyhow...who makes/manufactures such a plug at this time, and what would the #s be?

Or, does anyone make the old, 1-2-3-4 heat range plugs?



Posts: 150
Location: Carver, MN

The Champion D-16 is equivalent to the #3 and the D-14 is a step colder: equivalent to a#4. I have not noticed that any other manufacturers offer more than one heat range. NGK lists their A6 as the replacement for both the D-14 & D-16.

Posts: 470
Location: Six miles East of Cheney, Wa.
Hey thanks. Plugs in it now are D16's, but I didn't know if that was the right plug, or even close. I have no doubt now that I fouled the rear cylinder with too rich a mixture, which was my stronger suspicion. First few times I ran the motor, both the idle and high speed needles were MANY turns out from where she's running now, which is very close, as she's running really nice, great throttle response, and all that. I believe the pump-shot is way stronger than it needs to be, but that's an easy fix.


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