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Thought I would share a bit of info as it occurs to me I see this issue pop up regularly on bike forums.

Taking the drain plug out and you notice some of the thread coming with it or the thread is badly stripped. What to do?

The thing to do depends on what size drain plug you have. If you are lucky it will be M14-1.50 and then you can buy an
oversize drain plug at almost any autoparts store. You have to measure the diameter of the plug and use a pitch gauge
or compare the thread to know thread on a bolt like a bolt with 1.50 thread pitch. Many bikes use M14-1.25 drain plug
bolts so your options just left off the oversized drain plug avenue. At least, I could never find one. By the way,
oversize drain bolts are thousands of an inch large than a normal bolt and when you screw it in, it cuts threads (same
pitch as original) just a little deeper. You can find OS, DOS and TOS (oversize, double oversize and triple oversize)
for some size drain plugs (but not an M14-1.25.

OK, what to do? Timesert sells a nifty kit to install a solid insert for about $130 (prices may be more of less depending
on where you can find a kit). They sell them in M14-1.25 pitch. Lisle also sells a drain thread repair kit in the same
size but for slightly less money; about $100 from what I can see. I decided to go with my old spark plug thread repair
kit from NAPA which is a Balkamp #77003223. It is about $45 and includes a tap and punch tool and 3 inserts, short,
medium and long. I suggest while there to get refills in the medium length which are about 1/2" long and are also
the correct size for spark plug thread repair. This size works perfectly for a drain bolt.

Now, what to do...

Step one, drain the oil (sorry, being sarcastic).

Step two, take the tap from the kit and using a 3/8" drive ratchet, copat the tap with heavy grease and insert into the
hole and it will thread onto existing thread because the starter part is tapered and is M14-1.25 pitch. The grease is
there to lube the tap and catch the metal shavings.

Step three. Turn the tap clock-wise for a little bit and remove it from the hole Use an old tooth brush to clean
off metal shavings and re-grease the tap and continue this process (in, out, clean then back in) until the thread on
the tap just about disappears into the hole. This means you are plenty deep enough and remove the tap.

Step four. OK, clean the thread on your drain plug with a wire brush. If the thread is nicked up, you can run a
die over it to clean it up. Coat the thread of the drain plug with grease (lightly). Screw the drain plug into
one of the medium inserts (or whichever makes sense in your application) with the knurled end of the insert towards
the outside (towards bolt head) and then coat the outside of the insert with hi-temp RTV gasket maker.

Step five. Wipe off the new thread in the hole to get all the oil off and put a paper towel in the hole for a bit
to sop up oil. Insert the drain plug with insert installed on it into the hole and tighten it down snug (you don't
need two hands on a breaker bar!). Once the plug/insert are snugged up, remove the drain plug.

Step six. Take the supplied tool that is used to punch the insert and put it in the insert. Tap it firmly (don't
beat it to death) and it expands the insert a little bit where the knurled end is and will seat the insert.

Step seven. Screw the drain plug in and torque to spec. I wouldn't remove the drain plug again until the RTV
has had a chance to set up but I suspect his bit is just being over-cautious. It won't come out anyway.

Step eight. Take a shower and scrub off all the engine oil that you have sopped up during this job.
 
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