so took in to have 2nd set of plugs replaced on my 2020 M8 with 57,000 miles..Service Writer put this on the table and said upon removal it had broke off..they are obviously taking care of it all, new head, whatever it takes, because they put the old spark plugs in at 27,000 miles..never had this happen in all my bikes, years, miles, etc...wondering if maybe he had cross threaded it, or used Red Loctite instead of thread antisense....like using Ben Gay instead to toothpaste oh well, said two weeks eta worst case scenario..at least it's November and not peak touring season

 

That's a weird issue. Plugs are usually pretty durable and will take out threads before they break like that. Sorry that happened to your bike.

 

indeed..did not see that coming! just had it in for the brake light recall and it's been 30K since plugs were changed, only charge $100 and some change for plugs changed and I have a $100 Ride365 Gift card from Harley, so figured it'd be in and out quick, free and easy and I'd be riding..I thought wrong..chalking this up to the '$h!t Happens' category

edit: I'm not counting this as a problem and still consider my bike 100% problem free !!!

 

It would be interesting to know how that plug scenario would have played out if you were the one taking it out MJ? I mean, if you snapped it, it'd be on you, right? Lucky thing you went down the path that you did, huh?

 

It's never occurred to me to leave plugs in for 30,000 mi. Is that the correct interval for a 2020 m8..?
I wonder if plugs "sticking" in place like that is going to be a more common issue if people are leaving them in place for such a long time.

 

Would like to see how they get the remaining broken piece out with no cylinder head damage. Consider having them put anti-seize on the replacement plugs to help minimize this problem again.

 

uhh...pretty sure mjwebb said they were going to get a brand new head.

 

A reputable machinist will get that broken plug out easily without damaging the head (removed from engine of course).

According to the service manual, spark plug threads should be clean and dry.

 

My guess is that they were over-tightened at install.

Spark plugs in bikes are easily good for 30K miles. Keep in mind that some automotive spark plugs are intended to go 100K. Those come out without issue (usually). While corrosion could happen and cause seizure, it isn't very common. And with the miles MJ puts on his bike, I doubt they were in there all that terribly long time-wise.

 

in response..HD accepts full accountability, whatever it takes even if it needs a new head, or whatever..and yes, I'm glad now I didn't DIY these... I would not have used anti seize but I sure would not have over tightened them..once the washer makes contact about 1/4 turn is all they ever need..it's only about 10-12 lbs tq IIRC..who knows how the previous tech installed it or if it's even possible the plug itself had a weak point..since I ride a lot the 30,000 miles only took me 18 months so sooner than the 2 year service schedule calls for..some people might need many years to put on 30K and that's too long to leave plugs in imo...when I had the originals replaced at 27,000 miles I could tell zero difference in performance which is why I let them go the full 30K this time as recommended and it was running like new at that..like many with Twin Cams, I would replace spark plugs annually at minimum because it was like $10 and a few minutes to do so...think the manuals said to clean and inspect every 5 or 10 K but if I was pulling them out they were getting replaced with new

edit: they are looking at a loaner bike for me for the two weeks it may take..or I could ride my wife's CVO trike