Stripped Spark Plug Threads

[Lowcountry]

Need to repair, would this be the recommended Time-Sert kit? 1973 Eldorado.
Using NGK BPR6ES plugs

https://www.amazon.com/Time-Sert-M14x1-25-thread-repair-4412-321/dp/B077YTC4CP/ref=psdc_15709101_t3_B0025NL1V2

[lucian]

    The best choice , just be careful about getting any swarf in the cylinder while tapping the plug hole.  best done with the head on the bench.   

[Scout63]

I like timeserts, but would only consider installing one with the head off.  If the heads haven’t been cleaned up in a hike, this might be a great time to take them to a good machinist to check valves and guides, and repair the plug threads at the same time.

[dirtiegirtie]

I've used a time-sert kit for just this occasion; to repair a stripped spark plug hole on a Honda Nighthawk.

I can't imagine doing the repair with the head still on the engine. I read some folks would position the piston in the lowest position and fill it with shaving cream > tap the hole > turn engine and push the shaving cream filled with metal filings out through the same hole... I just couldn't see taking the chance

As for the time-sert kit - What an easy to use and extremely strong solution! Take the head off and do it right, and I have no doubt the repair will last longer than you own the bike.

[Rough Edge racing]

 I have done more than a few Timeserts, far better and more expensive than Heliciols. The insert must be installed square to the existing sparkplug seat area... A drill bit guide is helpful if done with the head in place...I know that 10's of thousands of spark plug holes  on various engines have been repaired with head on the engine..But the Guzzi head removal is no big deal..
  Doing Timeserts on one of my Brit bikes...Head bolt stripped, pulled the head and cylinder so the job could be done square and true on a drill press

[Moparnut72]

I mess around with and have raced old Mercury outboards. They only have 3/8's of an inch of threads in an aluminum "head", no head blind bore. They are prone to stripped threads. We would have to disassemble the whole engine to take the "head" off so we would Helicoil these on a regular basis even between heats. We put grease on the tap to capture the filings. I have never heard of any damage damage or failures. I have even done it on my son's Suzuki car. However Timeserts are better, use one of those.
kk

[John A]

I've used greased taps without incident.  Roll the engine so the piston is safely down and both valves are open before starting the job.  Piston down keeps anything from touching the crown, but try to keep it up as much as possible while still ensuring that the tools won't contact the crown.  In that position, if you think swarf may have gotten past the grease, you can blow it out the exhaust.  Keeping the piston up as high as is safe reduces the volume that the swarf can get into.

The real challenge is getting the tap true to the bore.

Be careful of having the valves open when doing this or the drill or tap can nick the edge of the valve.
I prefer the valves closed to keep any errant particles from the valve seat where if it gets a valve closed on it will lead to bad things

[Madtownguzzi]

Here is a very good YouTube on repair of stripped spark plug threads with the head on the vehicle using grease on the tap.
 https://www.youtube.com/watch?v=B3irFj2XeCM

[Lowcountry]

Thanks for all of the replies, ordering the kit today.

[moto-uno]

  The similar jobs I've had to do with the head on involved threading a thick string heavily greased into the combustion
chamber . Well greased drill bit (used Heli-Coils) and same on tap . Not particularly fast but safe in a pinch .  Peter

[Chuck in Indiana]

I had a stripped plug in the Lario several years ago, so decided to do a test. I took the head off..really easy on a Guzzi, ya know.. and did all the things I knew of to keep swarf from getting into the cylinder.. greased drill, greased tap, etc. and installed the insert over a surface plate. Took a picture of all that would have gone into the cylinder despite my best efforts, and that's all I'll say about that. <shrug>