Optimax Stripped Sparkplug

So I am working on a 200 Optimax (3.0). Plugs looked like they hadn't been changed in a while and cylinder #2 was tough to get out. Looks like someone at some point cross threaded the first couple threads and you can see that they're pretty gummed up. I could force the sparkplug in but I would rather not do any more damage. Luckily the majority of the threads look perfect after you get past those first couple of turns

I have tapped holes before, never something quite this large. In my research I have found what is called a back-tap which threads from bottom to top, or from inside out. This seems perfect for this application because I want the tap to start at the threads that are perfect and continue up to wear they are damanged. I feel like if I were to tap the normal way I may not fall into the originall groove and may end up tapping new threads altogether. Any opinions on the matter? Seems pretty straightforward but maybe I am missing something.

Thank You

You might not have the same integrity after re threading the hole. If you choose to do it, grease the tap heavily (catch shavings) and have a good vac cleaner running to catch any loose shavings. Back tap is the correct tool. Also, you can get used cyl heads for 90 bucks on e-bay etc.

Quote:

---

Originally Posted by XstreamVking

You might not have the same integrity after re threading the hole. If you choose to do it, grease the tap heavily (catch shavings) and have a good vac cleaner running to catch any loose shavings. Back tap is the correct tool. Also, you can get used cyl heads for 90 bucks on e-bay etc.

---

I agree on the integrity. But I'd say only 15-20% of the threads are damaged. If it were any more I would be worried. I've already found a couple heads on ebay just looking around. And I'll definitely use some grease so the shavings stick to it

I have used the one in the link below. It is a reverse tap, so it is inserted, expanded and screwed out so the top threads get cleaned last. Just grease it to catch any shavings. Works great if just the top threads are buggered!

https://www.amazon.com/Back-Tap-12-M...ser+spark+plug

What size do I need?

Had a similar problem ended up changing the head

I ordered a 14mm according to the research I did. But a head change is plan b. Want to see if I can get on the water this weekend though.

After all this, I will never complain about working on my carbed 2.4 ever again.