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wow what's the best thing to use on a drain plug leak from the inner primary.
been dealing with this for years is there a cure let me know willing to try. and thanks in advance
First of all, are you sure it's the drain plug? There is a chain oiler hose and at least three transmission seals fairly close by above that area.
If it is a 1981 as your user name suggest, the shovelhead inner primary plug hole is setup for an o-ring. Be sure the o-ring isn't being damaged when tightening the drain plug. With the plug out, look that the sealing surface is in good condition, no nicks or other raised areas that may damage the o-ring.
If all else checks out and the leak remains, I'd try a flat nitrile washer to see if that will seal any better. And after that I'd try some non hardening thread sealer. I'd avoid teflon thread tape and use it only as a last option. And be careful to not over tighten the drain plug, which could contribute to a damaged / cut o-ring. Or worse, strip out the threads.
For me anyway, the best way is to pull the transmission, gut it, have the drain plug hole filled, drill and retap hole for 1/8-27 NPT with a magnetic drain plug. Those original thread holes are most likely really worn out and things like teflon tape and pipe top are not going to solve your problem in the long run. Another option is to use an oversize plug. Places like V-Twin sells them.
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Last edited by panz4ever; Feb 9, 2024 at 10:48 AM.
Lots of good advice, but the first one is are you sure where it is leaking from? I was chasing a leaking oil tank drain plug for a year, turned out the tank was cracked at the bottom mount and leaking, plug was fine. It is not easy under the bike to determine the source, good luck.
On my '77 FXS it wasn't the drain plug that was leaking, it was the transmission mainshaft seal. GUNK the underside really well, ride the bike a few miles then jack it up and have a look.
On my '77 FXS it wasn't the drain plug that was leaking, it was the transmission mainshaft seal. GUNK the underside really well, ride the bike a few miles then jack it up and have a look.
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drain plug troubles.
