Heli Coil Leaking?

9 replies to this topic
  • markcjr

Posted March 23, 2014 - 04:44 PM


So I stripped my crank case drain plug (threads came out with bolt).   I drilled it out and heli coiled it (perma coil actually)  I set the threads about a turn or two in from the bottom of the case so my drain plug wouldn't hit the threads.  I got a crush washer from napa, and it's a thing copper one.  Would the thicker aluminum one work better, the kind from the the dealershiip?

Did not use locktite on perma coil.  can always remove and and reinstall with locktite.  If I do that, do i apply locktite all around the insert?  Hopefully just a more robust crush washer will take care of the slow leak.



Edited by markcjr, March 23, 2014 - 04:46 PM.

  • nuity5

Posted March 23, 2014 - 05:49 PM


As long as your sealing washer is larger than the od of the thread insert it doesn't matter if there is anything sealing the outside of the insert. One thing you can try real quick is just to loosen and tighten it a few times. Just crack it a quarter turn and tighten it back up. Doing this a few times will crush the washer a little more and does help sometimes. You might have a copper washer that is a little on the hard side or there might be a small scratch or nick on the case where it has to seal. My yz250f has a nick and would weep around the drain plug. My solution was to countersink the drain hole and then use an oring on the drain bolt. Seals perfect - just have to replace the oring every oil change but they're dirt cheap. Hopefully you don't have that problem but there is a solution if you do. Clay

  • markcjr

Posted March 23, 2014 - 07:22 PM


Thanks Clay,


so you use a rubber o ring instead of a crush washer?

  • Zimman

Posted March 23, 2014 - 07:33 PM


if the threads are leaking you can try  wiping  the drain plug threads with Teflon paste found in  the plumbing section



  • grayracer513

Posted March 23, 2014 - 09:04 PM


What has most likely happened here is that the threaded hole isn't square with the surface that the crush washer seats down on anymore since it was repaired.  If that's the case, the hole needs to be spot faced.

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  • nuity5

Posted March 24, 2014 - 12:04 PM


Gray racer mentioned another very real possibility. I did use an oring but you have to countersink an area to contain the oring. If you don't contain it there is zero chance that it will work. I'm going to change the oil in my 250 later this week and I can take a picture of what I'm talking about. Clay

  • markcjr

Posted March 26, 2014 - 12:28 PM


Thanks clay, pictures would be helpful.  Do you just use a larger diameter drill bit to recess the oring?

  • bg10459

Posted March 26, 2014 - 12:39 PM


What has most likely happened here is that the threaded hole isn't square with the surface that the crush washer seats down on anymore since it was repaired.  If that's the case, the hole needs to be spot faced.

My thoughts exactly.  Install the drain bolt (without the washer) till it just touches the case and see if one side of the bolt isn't touching.

  • markcjr

Posted March 28, 2014 - 04:48 PM


Well, today I untightened the drain plug and retightented a few times and it hasn't leaked in the past 5 hours.  I'll let it sit overnight and then fire it up tomorrow and see what happens.  Hopefully it was just a tough crush washer as someone suggested above.  I'll keep you posted and thanks for the suggestions.



  • nuity5

Posted March 30, 2014 - 04:26 PM


Sorry I'm a little late on the pics. Sounds like you've got it solved though. Anyway first pic is the countersink. Guess I should have pulled the shifter for a better pic but you get the idea. Second is the orings I use and third pic shows how squeezing it into the threads chews it up so you can't really reuse them but 100 of them were only a few bucks. Hopefully you won't need any of this. Clay




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