Now that I've fixed the stripped threads on my '99 Road King's twin cam oil drain plug, I thought it be best to pass along my experience for others. This seems to be a very common problem due to a steel drain plug and an aluminum pan... Somehow my bike made it 18 years and god only knows how many oil changes before the pan's threads gave up.

Several repair choices are available and I've included the reason why I did or didn't utilize the particular option...

1) A new oil pan. This is probably the best option, especially if you want to increase oil capacity via a Baker pan which accommodates an extra quart or quart and a half of oil. However, pan removal and replacement is not an easy task which is outlined on other threads in this forum (search "pan removal").

2) A time-sert or helicoil. The time-sert is probably the better option of the two but getting a drill between the bottom of the crankcase and the oil pan requires a 90 degree drill (at least based on what I read). And while removing the pan makes the time-sert or helical option easier, why not just replace there pan?

3) An oversized plug. This is the option I chose and, at this point, am happy with the way it turned out. If I have any long-term issues I'll post them here but I don't forsee any problems (see piggyback plug in picture).

I chose to go with a piggyback plug so that when I change the oil, I'm removing/replacing a steel drain plug into a steel receptacle and not a softer, aluminum pan. This should aid in the longevity of the threads. I purchased a Dorman piggyback plug (1/2"-20 single oversize)...

I also purchased a 1/2"-20 single oversize tap. The length of the tap is short enough to run into the drain hole straight without interference with other engine components. I created new threads in the drain hole using the single oversize tap. Take extra precautions when cutting the threads to prevent metal shavings from collecting in the drain pan. While it is outlined in other threads here, I'll just touch on a few things: coat the tap with vaseline or grease to trap the metal shavings, clean the tap after every revolution or two while cutting the threads, and do numerous "flushes" of the pan/crankcase with kerosene and oil to clean the new threads you're cutting.

Once I cut the new threads, the piggyback drain plug I bought wouldn't go into the drain hole. The tip of the plug wasn't tapered so I bought a 1/2"-20 single oversize drain plug that WAS tapered (local auto parts store) to begin the cuts in the new threads. This paved the way for the piggyback plug I purchased. Both drain plugs had the same diameter shank but I needed a tapered plug to start the plug into the new hole (see tap in picture).

Anyway, the new plug went into the pan without difficulty. Because it was still somewhat cutting new threads, it was snug going in... I used a small (short) 3/8" ratchet and it required some effort bit nothing overwhelming. You shouldn't need anything longer such as a breaker bar.

It is also recommended that you use (like I did) some 10mm or 3/8" sealing washers on the "piggyback" plug since a normal o-ring may squish out and not seal (see picture of sealing washers).

Anyway, that seems to work for now... I'll update in the future if anything else comes up. There are other threads on this forum that address this common issue, so check some of those out as well and apply whatever you need for your particular application.

-Carl

 

This post/thread has been a great help with may good options.

I too had a transmission plug on a 2012 Softail Deluxe bind or appear to cross thread on the first fluid change. My daughter bought the bike new and only put 800 miles on it in five years. Brand new bike, only five years in the garage and not on the road.

I decide to change the fluids before she sold it to a close friend. Man what a bad place for a transmission plug between the two shocks. Plug came out easy went back in hard. Spent about an hour trying to get it tightened it until I thought it was seated properly and hoping and praying it was not cross threaded. After a long ride we had a leak (crap).

So I contemplated all of the options in this post/thread. I settled on chasing the treads first, I was pleasantly surprised that it fix the problem immediately. I put axle grease on the end of the tap and ran it two times cleaning it in between. The first cleaning had some metal residue but he second one was clean. I then ran a little clean transmission fluid thru it and cleaned up the mess. The 1/2" x 20 plug went in sooo smooth. Now we have no leaks and everyone is riding again.

My .25 cents would be to always chase the threads first. Was great advise!

Sike

 

what size tap did you use to "chase the threads" 1/2x20?

 

Looks like I have the same issue! That said, it looks like I am missing 6 threads! think this would work? Or should I go up 1 size in the bolt and hole?

 

Apologies, I failed to notice the OVERSIZE on both the tap and bolt!