Not directly Triumph related but rightly or wrongly I tend to trust the advice I see on this forum over most others! So having found that the thread in a 30 year old ally sump is not up to 30Nm applied to the drain plug, which repair is best? Helicoil or tap and fit a larger bolt - or is there a third way??
On a drain plug? Use PTFE plumbing tape and worry a bit less about the ‘right’ torque. Otherwise re-tapping is more likely to produce a seep free result than a helicoil but it’s a bit 6 of one, half a dozen of the other and (without knowing what it is) things like ‘concours’ and originality might creep in to the equation.
As Cal has mentioned a way forward, if you are worried about having to remove the plug each oil drain you could if wanted fit one of these once and not have to disturb the threads again, "just a thought" http://www.stahlbus.com/products/en/oil-drain-valve/
Have to say 30NMT seems too much torque to me for a metal bolt in an alloy sump are you sure that is right? what size is the bolt thread?
It's an M14, and that's the setting given in the Yamaha workshop manual. As it turns out you're right - it's too high!
With all the autos and bikes I’ve ever had I just snugged the drain pug up a bit, never had one leak. 30nm does seem overdoing it!
Seems a lot of sump plugs are in the 25 to 30Nm range, does seem over the top to me, I always nip mine up to around 12Nm then apply a blob of Sicaflex to the head of the plug and onto the crank case, that way I’m sure I’ll never strip the threads and sure it’ll never unwind.
I've done both Time-Sert & Helicoil repairs - either one is a good choice What is important when doing this is that the new tap needs to be PERFECTLY perpendicular otherwise you can potentially end up with the plug not being parallel to the seat and then it can leak. One way to ensure that is good is a Sav-a-thread kit That has a special cutter that starts by threading into the existing thread and follows that before starting the new cut/ream and re-thread - so if the original thread was 'true' (which it would be) then the new thread for the coil will be also. Tip - use a LOT of grease on the cutting tool to help catch all the swarf and then flush some oil down through your sump out through the open hole to remove any that may be around the lip on the inside So then you end up with an OEM size plug - just always be sure to use a new washer when you re-install. This kit is really inexpensive too (check Amazon, Ebay) You can see exactly how the cutter works from the image below
