Spark plug question
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From: Brick NJ
Spark plug question
Since I’m running the 10.1 piston would anyone recommend running a colder plug. Currently I have a NGK BPR5 wondering if going to the 6 is better for the engine? Just a thought guys
Road Master
Joined: Mar 2012
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From: Ohio
Stock heat range is fine. Street ridden bikes seldom see any need for changing the heat range. In any case I assume that you have changed the camshaft as well. So the corrected compression (which is the important compression value) may be same or even less than a stock motor.
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From: Idaho Panhandle
You ought to be able to read your plugs after 1000 miles. A really good reader could diagnose at 500, but it takes me a while to really understand what the plug is telling me. Don’t jump until you know what the issue you want to resolve is, then correct gap, plug, or map.
Last edited by son of the hounds; Sep 29, 2025 at 08:19 PM.
Seasoned HDF Member
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From: Idaho Panhandle
smart move, gap first, the ride, then analyze.
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From: Poolville
The BPR5ES-11 is one of the best plugs for a modified Evo, the Autolite is also very good.. Gap to .038" for 10:1 comp and the EV 46. What jets you running in the S&S E?
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From: Florida
For plug gap I run hard all the way to 5th gear at around 5,800-6,000 rpm. If the motor did not cut out… I widen the gap until it does cut out.. then I close the gap 2-3 degrees and retest for no cutting out. I run between 50 & 55 thou gap on the soft tail and 48-50 on the Road king.
I test coils this way as well. After thousands and thousands of dollars spent on industry hyped ignitions I truly believe the Dyna S with a 90 OEM coil from Harley is the hottest fatest spark you can have under a consistant load. Oddly I only have it in the Shovel. I’m running the 2000i in the EVO’s with a quality 90’s style three post coil.
I test coils this way as well. After thousands and thousands of dollars spent on industry hyped ignitions I truly believe the Dyna S with a 90 OEM coil from Harley is the hottest fatest spark you can have under a consistant load. Oddly I only have it in the Shovel. I’m running the 2000i in the EVO’s with a quality 90’s style three post coil.
Last edited by Rains2much; Sep 30, 2025 at 08:23 AM.
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From: Brick NJ
The jetting I haven’t touched, its what came in it from S&S.
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