Oil drain stripped

The good news is I just got back from a 400 mi epic loop through Joshua Tree National Park from San Diego. I had a small oil drip when I left which got progressively bigger that I'm pretty sure is the upper oil pan spacer gasket.

I already have the gaskets on hand and was getting ready to drop the pan and spacer. When I tightened the oil plug it stripped pretty easily. I think it's probably an aluminum pan and the bolt is steel so eventually it's going to strip the pan out. I've probably done a dozen oil changes over it's life so far.

Had this happened on many other bikes this would be a big problem but dropping the pan here is easy and I was doing it anyway like I said so I was wondering if anybody has upsized the oil drain plug and rethreaded and which plug did you use if so? How did it work out for you?

If you get a stainless re-coil / helicoil insert fitted then you can retain the original size plug and washer.
It will also be much stronger and more reliable than the original thread - a mini upgrade!.
Check the plug. Over time the plug can stretch and this damages the threaded hole.
Way back when, service engineers would run a die nut down the drain plugs every service to ensure that the pitch was still correct. These days many manufacturers recommend a new plug every oil drain.

If you are going to the trouble of drilling and tapping the sump for the next size-up plug, I would suggest installing a time-sert with original thread/pitch size as a more durable repair.
Drilling and tapping for a bigger drain plug will still leave you with a steel plug in threaded alumimun, it will wear the same as original and might fail down the road. The time-sert fix will give you a more dependable steel on steel interface.
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+1 on Timesert. I used one to repair my GRiSO's transmission/gearbox drain plug, in situ. Not hard.

By the way, the transmission case material is thinner at the drain plug compared to my T3. This makes it easier to strip the threads. I wonder if the same is true for newer oil pans.

Question to the experts: is there any value to replacing the drain plug every so many years or changes? I’ve had no problems at almost 9 years with yearly oil changes.
Thanks!

I have had no problems except that one time I must have over-tourqued the transmission drain plug. Dave Richardson did recommend helicoiling the final drive plugs whenever the drive was apart.

Drain plugs - I gave up hand tightening years ago

there is too much at stake if you strip it and torque wrenches are relatively cheap now

JohnA wrote:

Question to the experts: is there any value to replacing the drain plug every so many years or changes? I’ve had no problems at almost 9 years with yearly oil changes.
Thanks!

No.

Argh, so I dropped the pan and spacer then fixed the drain plug with a heli-coil. That all went great but oil leak is still there and I found the source is the crankshaft rear main seal. Oh joy, just the Christmas present I wanted. .

It's been done before on this bike due to the rear flange bolts being too long years ago. I may tackle this myself this time. Can I do it just by removing the CARC and gearbox or does the engine need to come out also?

The engine needs to be dropped. It's a fairly major undertaking but doable at home with the help of a couple of mates.

If it's leaking again there is probably a reason as usually if it is done right the fix is permanent and very reliable.

There were a couple of issues with these early engines. Firstly there was the two lower bolts bottoming out before they clamped the flange. Then there was a problem with the oil feed dowel being slightly too long and the o-ring that is supposed to seal it being slightly too thin.

The bolts were probably addressed first time around but chances are the oil feed dowel and o-ring issues weren't, or at least not adequately. The length of the dowel is easily addressed. Simply give it a few strokes with a smooth cut file and take 20 thou/1/2 a mm off it. The o-ring can also be substituted with one with a slightly larger cross section. Finally, when the flange is refitted it is important that NO GASKET IS USED. Just a very thin smear of Threebond 1211 or equivalent.

Other sources of leaks may be the rear mainseal, the idler shaft cover o-ring or the LH cylinder cam chain tensioner mounting bolt cover plug o-ring but all three of these would be rare failures and very bad luck.

I noticed it seemed worse immediately after doing the pan and spacer gaskets but then it was cleaned up enough that I saw a couple of drops of oil come out at the bottom of the gearbox bell housing where there's an oval cut out. That means the main seal right? Where would it leak from if the oil dowel was the issue? Thanks again!

Nope. People always jump to the conclusion it’s the rear main, and it may be. But as I said the rear main, which is a Viton seal, is very dependable unless abused.

The o-ring I mentioned first up is on the oil feed dowel to the rear main bearing flange.

Hm, funny you should mention that because the dowel was removed when I did the gaskets and now the leak is about 3x bigger.  How does that make the oil come out of the bell housing area?  You might have just saved me a bunch of money and frustration! . Perhaps I am mistaking the oil pickup tube with said dowel?

You are.

The dowel is in the rear main bearing flange.

Pics in this thread on the AF1 board.

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Is this the dowel you are talking about?  The entire rear flange was replaced albeit about 15k miles ago.  It worked well except for the part where the mechanic put the clutch actuator rod in backwards and it milled out the pressure plate requiring another do over.
It sounded like a Ducati dry clutch rattle right up until I couldn't disengage the clutch anymore.

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That's the one John. Was the flange reinstalled with a gasket?

I'm not certain. It was a long time ago by a newer dealer in Portland. Either way it sounds like the entire drivetrain needs to be removed? That's probably more than I can do so likely retiring the bike until I can pay the $1500 or might sell to someone more capable? Bummer!

You sound capable enough ... tho that may be "damning with faint praise" as it comes from me, someone who sees checking tire PSI as depot-level maintenance.  

But, after all, it is winter, and those of us not Downunder need entertainment, so I urge you drive on and document your adventure.  

Seriously, best wishes on whatever course you take,

Bill

moto wrote:

+1 on Timesert. I used one to repair my GRiSO's transmission/gearbox drain plug, in situ. Not hard.

By the way, the transmission case material is thinner at the drain plug compared to my T3. This makes it easier to strip the threads. I wonder if the same is true for newer oil pans.

The last time I drained the trans fluid, I felt that 'telltale' squish on the final snug of the bolt. No drips or leaking the last 2 years. That was at 12K, and the fluid coming out looked the same as what went in. I may just leave it. Due to spreading time between 4-5 bikes, I only put 1K miles a year average on the GRiSO, so won't worry about it until 2026 ;-) Unless I get caught out in the rain and lose the enclosed climate controlled garage, I may never change it.