I had recently sold an '02 Heritage Softail to a friend. He called me up over the weekend & told me he couldn't get his drain plug out to change the oil. I went down to his house & popped the plug out no problem & proceded to drain the oil. He asked me how I did it so easily. I told him- 1/4" hex & a 3/8" ratchet & some elbow grease. He looked under the bike while the oil was draining & he's shouts "which plug did you drop!?!?" like I was punching his ailing mother in the stomach. I get up & I'm like "huh?".

He got on the ground & showed me what looked like a pipe plug @ the bottom of the engine more so to the right of the bike. I've never even noticed this plug before as I was shown in the very beginning where the drain plug usually is. I checked under my wife's & my bike & they also have one(mine looks like it's a torx, though). I told him I have no idea what it is. He said the plug's 1/4" hex too. I took the hex socket & besides the fact he rounded the inside a little, the socket fit. I showed him where the actual drain plug is & not to mess with the other one until we found out what it is and/or what it does. So.......here I am, asking what it's for & what it does. Thanks in advance.

 

It is not used for draining the engine as you know and a few guys have cracked their cases removing it. The only reason I could imagine using it would be to see if the engine is sumping leaving oil in the case. The twin cam has 2 pumps in it as it is a dry sump system. One pump picks the oil up from the case and pumps it into the oil tank and the other pumps oil into the engine for lubrication. You should only get a few ounces out of there and could crack the cases as it is a thin spot. Tell your buddy never to remove it.

 

Best to leave it alone.. some have even cracked their cases removing it.

I've read its there because of the way the cases are made and others say its for some machining after the motor is put together, then I've read its to drain the sump if Ur motor has too much oil in the sump. ???

Those who have removed say U'll only get 3-5 oz's of oil out of the sump so what ever is the reason its there, its just best to not mess with it.

If U do remove it and crack the cases,, Well,, that's about as bad as U can get. U'll need a total overhaul and new cases..


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PHEW! That's awesome that he didn't bust it loose! Lucky for him, the hex rounded out & he couldn't get another bite on it. Thanks for the info, guys. This info will save him from making an expensive & costly mistake!

 

The was a guy here who did that very thing and cracked the engine case. He (if I remember right) JB Welded that badboy back in there and he's riding it today. He provided photos of the repair and looking at the work I'd say that guy will NEVER be stranded.

 

Good that he got it fixed... but,,, I'd rather not have cracked them in the first place,,

Most that take that plug out, does it thinking its the oil drain... NOT..


I also read couple yrs back some one patched his after he cracked them, and then sold the bike..

I wouldn't want that one...





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I asked about that plug when I went through the factory in KC and I really didn't get an answer, as they didn't build the engines there. I finally found a mechanic who told me it's put in there during engine manufacture and to not remove it. The manual does not say to remove it during an oil change.

 

My son bought a Harley oil temp gauge and that plug is exactly where Harley said to put the probe for the oil temp gauge.

 

Better to have them install it then...

 

I pulled mine yesterday by mistake, and found this thread while trying to figure out what it was. I damn near had a friggin grabber It's back in, ran it hot, and it's not leaking, so am praying I got away with it.....