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Discussion Starter · #1 · (Edited)
Hey guys, Im looking to do some work on a stripped oil drain plug before the season starts, Im just having some confusion about picking the right size repair kit. The bike is a 2015 wee, with a '12x20' drain bolt (seen here), but I haven't been able to find anywhere mentioning if its a 1.25 or 1.5 thread pitch. Unfortunately the bike and I are currently living on opposite ends of the country, so Im unable to check the bolt myself, just hoping to get some prep-work and parts orders done before we are re-united.

My thoughts are either to buy a time-sert and do the repair myself, or to buy an oversize plug so that I can ride the bike to the mechanic for them to do the repair (closest mechanic is ~1hr drive)

Ive read through MANY posts talking about these repairs, but some posts use a size-up time sert (M14 time-sert on an original M12 thread hole), and some use the same size time-sert as the original (M12 on M12). Is a size-up required, or does it depend on how bad the threading is stripped? Does this same logic apply for an oversize bolt (M14 oversize bolt required for an M12 original thread hole, or is an M12 oversize sufficient for an M12 original?)

So, is a diameter size-up required for time-serts and oversize plugs? Does the new thread pitch have to match the old, or can it be sized-up? Many thanks for any responses received!
 

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some posts use a size-up time sert (M14 time-sert on an original M12 thread hole), and some use the same size time-sert as the original (M12 on M12).
When you do a time-sert or heli-coil you first cut away essentially all the old threads, and in the remaining hole you now cut a slightly oversize thread. So an M12 really becomes something like an M12.6. You then insert the time-sert or heli-coil to bring the thread back to M12. This means you can now reuse the original bolt.

I don't see any reason to go from an M12 stripped thread to an M14.6 cut hole and then inserting a time-sert or heli-coil to bring it back to M14. If I had an M12 hole that was so badly damaged that an M12 time-sert solution would not work, I would simply drill and cut for M14 threads directly and not use a time-sert at all.

The other consideration is that your sump is thin-walled, and there's only a limited amount of material available to work with anyway. The more you drill and cut away to go to ever increasing sizes of holes, the less material is left over for the next time.

Having said all that, have you considered another solution: Use whatever thread remains, plus some JB Weld, loctite, teflon tape or whatever, to put an oil drain plug in there that has an integrated valve. This means that once you get the bolt in and sealed, you'll never have to undo it again. Something like this:

or
 

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Discussion Starter · #5 ·
My spare 2015 DL650A oil drain plug bolt measures 1.25 thread pitch.
Perfect! Thanks for the clarification :D

When you do a time-sert or heli-coil you first cut away essentially all the old threads, and in the remaining hole you now cut a slightly oversize thread. So an M12 really becomes something like an M12.6. You then insert the time-sert or heli-coil to bring the thread back to M12. This means you can now reuse the original bolt.

I don't see any reason to go from an M12 stripped thread to an M14.6 cut hole and then inserting a time-sert or heli-coil to bring it back to M14. If I had an M12 hole that was so badly damaged that an M12 time-sert solution would not work, I would simply drill and cut for M14 threads directly and not use a time-sert at all.

The other consideration is that your sump is thin-walled, and there's only a limited amount of material available to work with anyway. The more you drill and cut away to go to ever increasing sizes of holes, the less material is left over for the next time.

Having said all that, have you considered another solution: Use whatever thread remains, plus some JB Weld, loctite, teflon tape or whatever, to put an oil drain plug in there that has an integrated valve. This means that once you get the bolt in and sealed, you'll never have to undo it again. Something like this:

or
That is a great explanation! Thanks a lot for clearing that up, I will stick to the M12 time-sert if I go that route. I was also thinking of trying your last suggestion, using perhaps teflon tape to see if that will provide enough of a seal. The threads may be too far gone, but that will be my first go. I managed to provide enough of a quick-fix seal using a garden hose gasket and an o-ring (obviously unride-able, but sufficient for winter storage without leaking), so perhaps it's possible.

I was also looking at those 2 items exactly, my only concern is without a skid plate, the valve may be the lowest hanging part which makes me a little nervous, but will definitely be part of my consideration as they seem very handy. There was another Fumoto valve I was looking at that you may be interested in as well here, designed specifically for motorcycles. I do like that yours has a straight down drain though- seems more logical with gravity.

That entire thread is an interesting and helpful read- thanks for that! The item mentioned (here) I have not heard of before. Initially I was very impressed, but thinking more (correct me if Im wrong), I don't know if it will actually help. Although the 'piggyback' threads and bolts are both steel, the case is still aluminum. So, once the piggyback bolt is fastened, any additional pressure will still be transferred down the bolt to the aluminum casing, causing stripping all the same. Again, just my thinking on it, but maybe someone else can say differently?

I greatly appreciate all 3 responses, these were very helpful to me so far!
 

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Go into an auto parts store and they'll have oversized self tapping drain plugs with a smaller drain plug in the center. They screw in (with help) and job done. This is a common problem.
You use the nuclear option on the new drain plug. (Permanent locktite). The inner plug is the only thing that'll move.
 

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Discussion Starter · #7 · (Edited)
Go into an auto parts store and they'll have oversized self tapping drain plugs with a smaller drain plug in the center. They screw in (with help) and job done. This is a common problem.
You use the nuclear option on the new drain plug. (Permanent locktite). The inner plug is the only thing that'll move.
Would you suggest using these even without a skid plate? If a rock or something were to hit this plug, couldn't it cause some serious issues, especially if the base plug is permanently locked in? I do like the ease of the installation though, and it is quite cheaper than buying a time-sert kit
 

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It's a trade off, there is some protection there now for the plug, that cast spur on the engine, generally those replacement plugs are quite low profile so I wouldn't think the risk is much greater. If you can find some rubber hose or similar that'll slip on and stay put without increasing the profile that should be enough to take care of most glancing impacts.
 

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Discussion Starter · #9 ·
there is some protection there now for the plug, that cast spur on the engine, generally those replacement plugs are quite low profile so I wouldn't think the risk is much greater.
Thats a good point. I think I will purchase one of these plugs to see the size and will do a little risk evaluation once I'm back with my bike to see if I'm comfortable with it. Worst case, its a 10$ investment that I don't end up using, but I think it sounds pretty promising. Otherwise I will opt for the more expensive time-sert.

Thanks everyone for your input and suggestions! These were exactly what I was looking for :D
 

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Discussion Starter · #10 ·
I have been reunited with my bike, and have just completed my first 70km ride of the season today.

I ended up purchasing a piggyback plug from NAPA, as well as a set of 12mm (regular) and 7/16 (oversize) washers. I had a slow leak (few drops overnight) using one of the 12mm washers, so I decided to give the piggyback a go. I spent at least 40min trying to get it going, but I just couldnt get it to grab. Looking closely, I think the beginning threads in the case are the worst of them, so I'm thinking the piggyback didnt have enough to grab onto to pull its oversized self into the hole. Defeated, I decided to instead try using 2 washers on the original drain plug as a last ditch effort, and voila! It fastened very nicely, as with only 1 washer, it would tighten fine until the very end, where it would become loose again and pop threads. I left the bike overnight with no drips, put in some fresh oil, ran it idle for ~10mins, still no drips. Left it another night, did some short laps around my residence ~20-30km/h, no drips. Took it for a ride on the highway, roughly 70km round trip, up to 110km/hr, dry as a bone.

I will continue to do a few more shorter trips like these before I'm 100% convinced, but as of now, Im feeling pretty good! :D Thanks everyone for the tips and advice, it was much appreciated!
 

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I would advise to rather have an engineering shop look at this drain plug issue. I would think that the drain plug problem will only get worse each time that an oil change is done. You don't want that drain plug to fail when you are miles away from any help. The cost to repair the drain plug threads would be far less, than the cost of a replacement engine.
The engineering shop may advise a repair that could possibly range from, cutting new threads then fitting a larger sump bolt, to inserting a heli-coil or similar to allow for using the stock sump plug, etc, depending on how much you want to spend on the repair job. Have another look at the advice in #3 above on a more permanent the drain plug solution.
 

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Discussion Starter · #12 ·
I agree, it's probably not a life-long fix, and likely will get a bit worse with each change, but for now, after about 800km, it seems to be holding up.

I've played around with it a bit, it seems the aluminum & rubber washer I got from napa is the key. I also put some teflon tape on the threads, and installed a lockwire through the head of the drain plug for good measure. If the drain plug does fail in the future, I'm confident it wont be any worse than a very slow leak, which will give me plenty of time to bring it into a shop, or to try out options from #3 as you mentioned.

I'll continue to monitor it, but until then, enjoy the ride 🤙
 
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