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Had the same problem ... drilled it out and tapped it to 7/16 UNF ... I use a Stainless socket head cap screw that I undercut the bottom of the head a little to hold an o-ring ... I still use Teflon tape on the threads and have not had any problems ... I did remove the outer primary cover to do the work
I read all the posts and it sounds to me (duh) like the plug was over-tightened. So it's essentially jacked-up the outer primary. You can drill/tap for a larger plug. Or you can obtain another outer primary cover (with a nominal drain hole) and start over with a new 'stock' plug. As noted earlier, they are a tapered plug. For the record newer Harleys also have an o-ring seal. My '91 doesn't. Not sure what year they started that.
The plug on my bike didn't prevent a small drip every couple of days, when torqued to spec. I bought a new plug and tossed the old one. This solved my problem. I didn't use any goop. The plug was a couple bucks. It's too late for your outer primary, but for future reference.
Alan
Last edited by AlanStansbery; Sep 25, 2016 at 03:12 AM.
I read all the posts and it sounds to me (duh) like the plug was over-tightened. So it's essentially jacked-up the outer primary. You can drill/tap for a larger plug. Or you can obtain another outer primary cover (with a nominal drain hole) and start over with a new 'stock' plug. As noted earlier, they are a tapered plug. For the record newer Harleys also have an o-ring seal. My '91 doesn't. Not sure what year they started that.
The plug on my bike didn't prevent a small drip every couple of days, when torqued to spec. I bought a new plug and tossed the old one. This solved my problem. I didn't use any goop. The plug was a couple bucks. It's too late for your outer primary, but for future reference.
Alan
I actually did the same right after I bought my '91. Had the same issue as everyone else. Few drops here and there. After my 1st Primary oil change I noticed the plug allen socket wrench walls were wore from years of use. Got new plug for a few bucks. Used a little teflon tape. No leaks since. But this is obviously no help to the OP, LOL.
I'd drill and tap to next size up "Pipe Thread". That's important as pipe threads are tapered. If he doesn't have this capability or access to the tools to do so, a local machine shop or Harley service shop should be able to help out rather cheaply by taking in the Primary cover. Save on the labor charge that way.
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