Fixing Spark Plug Threads... the "easy" way?

[cupid]

I've come to find that the spark plug hole on cylinder 3 (3? the inner cylinder on the shifting side of the bike...) is all sorts of messed up. I have a helicoil kit on the way. With how tight the working area is with the engine intact, do you all think I might be better off pulling the engine apart? There's only one of me and I'm a novice with this level of work.

[Bob H]

I think the time to figure that out is when you have the helicoil kit in hand, and the needed tools.
My 1993 NH 750 has pretty good access to all plugs when the tank is off.

I did a helicoil spark plug repair 40 years ago... so if I was doing that project today I would watch a bunch of youtube videos with particular attention to how you prevent any metal bits from going down the hole into the cylinder.

[mollusc]

Cylinders are numbered left to right when you're sitting on the bike, so I think you're talking about #2.

How many miles on the bike?  I would be inclined to pull the head and do a refresh or possibly even replace it if I could find one for a decent price.  Being a self-confessed novice this level of work might be beyond you though.

[Bob H]

Interesting article that appears to be legit.
"Parts store kits that commonly fail are Dorman, Helicoil and Save- Thread."

"Don't work on the spark plug hole without first making sure the valves are closed. Open valves can be damaged by tooling and when blowing shavings out, open valves can allow debris further into the engine."

https://www.wiseautotools.com/blog/spark-plug-thread-repair-dos-and-donts/

"many of our customers call asking for a Helicoil kit. Helicoil is a brand name that's synonymous with thread repair. Just like Kleenex is the best known brand name for facial tissues, Heli Coil is the most common brand name for thread repair kits. But being the most commonly known name doesn't necessarily make it the best fix"

They recommend a different brand (Time Sert) with a different design

1. The Time Sert solid threaded bushing type inserts are loc-tited in. This is something that cannot be done with coil type inserts because you'd get loctite on the threads of the spark plug.

2. They are cold rolled. The bottom threads of Time Sert inserts are not completely finished. The threads are completed by the installation driver. This finishes the threads while expanding the bottom of the insert locking it into place.

https://www.wiseautotools.com/blog/timesert-or-helicoil/

They have a link to motorcycle spark plug repair, which unfortunately uses Harley as an example - but at least it gives more info on the process https://www.wiseautotools.com/blog/harley-davidson-spark-plug-thread-repair-how-to-fix/

If it was my bike I would research the crap out of it before installing a particular brand. Watch a bunch of different videos and try to find something not biased by the product seller.

[cupid]

How many miles on the bike?

Duly noted on the cylinder count! This bike has fewer than 10k miles which is why I'm reluctant to do anything too extensive if I can't help it.

[mollusc]

Miles are somewhat meaningless when you're talking about a 40 year old bike that may have had a less than stellar service history, so I wouldn't let that stop you from doing something substantial to repair the thing correctly.

[Glaswiegan2000]

Have you tried getting the proper tap and cleaning up the threads? If not its worth a shot, put some grease on the tap to trap the debris.

[Pete in PA]

The head does come off in the frame.
Or...get a bore scope to check for debris.  Vacuum it out through the plug hole with a small diameter hose taped to your shop vac.

[Gene]

Just a note:
When you run into a plug or bolt that is too tight, try this:

Work the plug back and forth. You'll notice that each time, you can unthread it a little further. Pretty soon, you'll have the plug out. When putting the plug back in,  use some anti-seize to prevent it from happening again.