As some of you heave read, I had a stripped spark plug hole that I wanted to repair. After doing research here, I purchased a spark plug repair kit at Kragens. It wasn't a HeliCoil, it was a "thin aluminum tube" threaded on the inside to accept a std 14mm spark plug, and threaded on the outside, too. The kit came with a tool for boring out the aluminum head to accept the insert. The tool is about 4" long with a drill-bit like front end, tapering to a tap-like back end. To use the tool, one "simply" insert it into the spark plug hole and attach a spark plug socket to it, and then hog out the hole with the drill bit end until the tool punches through the existing hole. You then continue boring but now with the thread tapping section of the tool, creating threads for the insert to screw into.

The result? Failure. Although I was careful to keep the tool as well-aligned as I could by hand, the hole still became oblonged and the insert would not seat well enough for my taste. It *did* seat, but, because of the elongation, I think that only about 1/4 of it's length had any bite and I simply was not comfortable with the end result. I was able to torque a plug into it, but I would never have had enough confidence in the repair to take a long trip without having a nagging worry that it would blow out at any moment.

I advise anyone who thinks they're going to do this by hand with a ratchet--as the instructions indicate--not to waste their time. Doing this repair well requires that you be able to accurately, securely mount the head onto a drill press table. Doing this with a hand-held ratchet is simply too imprecise. It was one hell of a lot of effort (about an hour of heavy-handed wratchet boring), and I still have the wound (well beyong a blister) to show for it.

Of course, your results may differ from mine but at least you now know one man's experience. So now I'm buying a set of stock remanufactured ported heads. I decided not to go with SE heads since they make their power at higher RPMs than my cam--and my riding style--calls for.

 

Well that sux.

So would your advice be to leave it for the experts to fix if a spark plug hole thread is stripped, or just go straight for the new heads ?

Did you strip the thread in the first place ? If so what advice would you give to avoid this (other than let a mechanic change your plugs) ?

 

That sucks. You made the right choice (in the end) to replace the head. I am sure you knew deep down inside that was your best option. I tried a kit years ago on a crappy dirtbike, and it failed! I will never do that again. In the end, I figured I would have already had the head removed after wasting my time.

I am not sure what a new or used head costs, but I would bring it to a machine shop and get an opinion after removing the head. They can do miracles sometimes.

 

I had one on the rear cylinder (dealer caused) took it in and they graciously fixed the problem asap , with apologies. Even though this is how it should be , it was a good experience.

 

That's a crapper. I've used Helicoils before, not the thing you listed, but there is definitely no room for error.

...maybe duct tape...

 

Best thing to do if you are doing you own maintaintance is to use the anti-seize on the threads and then use fingers only until seated then go for the rachet for the final torque. I have even used the socket WITHOUT the rachet to get to the more difficult plugs in some of the vehicles I have owned and have never had a problem, knock on the wooden head here. The biggest thing is that the heads are alumimun and softer than the plugs threads. I know it is a PITA but this is one place where slow is good. A smart move to remove the head so that you have the confidence to go out and ride and not have to worry about that roadside repair.

 

Bought mine used and found the back plug cross threaded, and no anti- sieze ever used! Pulled the head and just tapped out the hole to 14mm instead of 12mm. Called several spark plug companies tech lines and got part number for a 14mm plug with same heat index and properties of their suggested 12mm plug. (once you have a couple numbers, you can cross reference off index charts). So now have two size plug holes, but with correct plugs, working just fine.

 

Thanks for the follow-on adivce and observations. I'm sure others who have this trouble later will appreciate it.

iwant1:

Ideally, I'd suggest getting a "new" head. Buying a used one leaves you, potentially, with someone else's overtorqued plugs that are ready to strip. If you choose to buy used, get a waranty. Likewise, if you choose to have a pro do it, make sure they stand behind their work. After the insert is in, there's no way to tell if it's done well or not.

I put new plugs in the bike a month after buying it used. The threads seemed jacked-up on the rear cylinder (it took a while to get the plug started correctly when re-installing), so I think the threads were already jacked. They held the torque wrench setting I applied, but the threads ultimately failed.

I am in the process of purchasing a set of remanufactured, ported, stock heads with a one year warranty. I'm the first person to ask for a warranty, but you can see why, I'm sure.

Rocket350
Yeah, I pretty much expected this to fail but I was willing to give it a shot. After all was said and done, the buddy who helped me suggested I take the head to a machine shop and have them weld and re-drill the hole. I just decided I'd rather apply that $$$ to a set of used ported heads with a warranty.