Stripped Spark Plug Hole
Tourer
Joined: Jul 2021
Posts: 382
Likes: 251
From: Florida
You got off easier than I did. The first and only time I stripped a spa rk plug hole I sent the heads out to Big boys for time sert and a Street Port. I Also put a Big bore kit in. It was expensive but a fun repair. My spark plug blew out of the cylinder head while I was riding down the road stayed on the plug wire and was sparking . Drove home 10 miles on one cylinder. After I took the spark plug off the plug wire of course. I'll never install another spark plug without anti-seize and a torque wrench.
Tourer
Joined: Mar 2016
Posts: 466
Likes: 205
From: Long Island,NY
Worse. The spark plug grounds through the plug shell to the cylinder head. Anti seize can insulate the plug interrupting the ground path. Saw this at the GM Training Center on a car brought there by another dealer tech. Erratic misfire, moving from cylinder to cylinder, scope pattern was crazy. Pulled the plugs,cleaned off the anti-seize, reinstalled, no more misfire, perfect scope pattern. Tech spent a week chasing that issue,which he caused with anti seize.
Seasoned HDF Member
Joined: Dec 2005
Posts: 19,863
Likes: 7,981
From: poway
Worse. The spark plug grounds through the plug shell to the cylinder head. Anti seize can insulate the plug interrupting the ground path. Saw this at the GM Training Center on a car brought there by another dealer tech. Erratic misfire, moving from cylinder to cylinder, scope pattern was crazy. Pulled the plugs,cleaned off the anti-seize, reinstalled, no more misfire, perfect scope pattern. Tech spent a week chasing that issue,which he caused with anti seize.
Antisleeze is commonly made out of powdered copper or aluminum and high temp grease. It is typically conductive but molybdenum disulfide is not. Too much and a tapered plug hole may not ground a black oxide coated plug. Crush sealing washers help make contact.
The good thing is that most plugs now days have a conductive zinc or other coating.
Cruiser
Joined: Jan 2018
Posts: 113
Likes: 81
From: Southwest Michigan
As stated erlier I am pro anti-seize for spark plugs. The more the better, just dip as much of the plug in the jar and spin two or three times. Make sure your fingers are completly silver or copper colored. Loctite Stick, they have thread lockers and anti seize, silver or high temp copper, I use the copper. It is like chapstick, very neat to use and you can just put a little bit only on the threads. Just don't over tighten, I don't use a torque wrench for spark plug. (Yes, I was raised by a pack of wolves.) I am not a complete jack wagon, I only drive in the left lane to pass and no katchup on hot dogs.
Stellar HDF Member
Joined: Mar 2017
Posts: 2,589
Likes: 2,162
From: australia
i have experienced this, not with my HD but with my cb72 honda which has a ***** of a sparkplug hole to get at. I worked out what was happening fairly quick and washed it off the plug and it was all good to go....maybe i used too much , who knows?
Last edited by old mago; Jan 31, 2026 at 02:16 PM.
HD Forum Stories
The Best of Harley-Davidson for Lifelong Riders
8 Best Harley-Davidson Motorcycles Ever
Pouria Savadkouei
10 Worst Harley-Davidson Motorcycles Ever
Pouria Savadkouei
Killer Custom's Jail Break Is The Breakout That Refused to Blend In
Verdad Gallardo
Crazy Bunderbike Build Looks Amazing, But Is It Impossible to Ride?
Verdad Gallardo
Harley-Davidson Reveals Super Cool Cafe Racer Concept
Verdad Gallardo
Engraved Rebellion: Inside Bundnerbike's Glam Rock II
Verdad Gallardo
10 Motorcycles You Should Never Buy
Joe Kucinski
10 Things Harley-Davidson Needs to Fix in 2026
Verdad Gallardo
Southpaw Super Glide: A Left-Hand-Drive 1979 Harley FXE Built to Fit the Rider
Verdad Gallardo
Club Member
Joined: Mar 2021
Posts: 393
Likes: 308
From: Northern Cali
Well, I learned something today. I've never seen or heard of a expandable tap.
Also, I like your idea of checking your threads on new plugs before committing to installing them. Shouldn't have to, but mass produced stuff can be pretty cheesy these days. Actually, not even mass produced. Exhaust systems come to mind.
Also, I like your idea of checking your threads on new plugs before committing to installing them. Shouldn't have to, but mass produced stuff can be pretty cheesy these days. Actually, not even mass produced. Exhaust systems come to mind.
Thread
Thread Starter
Forum
Replies
Last Post
HDF Tech
Engine Mechanical Topics
1
Apr 2, 2015 05:56 PM
