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Discussion Starter #1
Hi folks,


I was changing the oil in my bike the other day and managed to strip part of the drain hole in my oil pan. It isn't leaking as it sits or at idle, but it also won't tighten down completely so I'm afraid to ride it. I'm planning to use a helicoil to fix it but I wanted to double check what size/pitch I need. I know the plug is a 13mm, but I don't see a 13mm helicoil and this being a H-D I suspect the true size is SAE, which would be ~33/64.


Also, perhaps an obvious question, but is a regular crush washer the appropriate one or do I need a special part? And should I remove the OEM rubber O-ring from the plug?


Appreciate any thoughts/advice!
 

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I recommend retreading it with a slightly larger plug. Most shops should have a tap and die set which can easily do it. Shouldn’t be much labor and only need to purchase a new plug bolt with washer. I haven’t looked at the one on the streets, but the washer is usually a brass or nylon one.
 

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Don't confuse the size of the bolt head, with the size of the threaded shank of the bolt. A set of cheap metric thread gauges will save you lots of heartache. You can find the thread gauges on e bay. You use them by selecting one leaf of the thread gauge and laying it's serrated edge along the thread of the bolt shank. If the serrations and the bolt thread mesh completely when you hold the gauge up to the light, you can then read the thread size which will be marked on that particular leaf.

Once you have determined the thread size, you'll need to assess the state of the stripped thread in the crankcases. If the thread isn't too badly damaged you may be able to use the original thread size tap to clean up the threads and make good. If you can do this coat the tap with grease so any swarf formed by the tapping will stick to the tap and not find its way into the engine. Wrapping the drain plug threads with a couple of turns of PTFE tape can also help with tightening up slightly loose meshing threads

If the thread is too badly stripped you might wish to replace it with a Helicoil insert, but this will be a complete pain in the ar*e, trying to drill out the stripped thread and insert the helicoil while laying on the floor working underneath the bike. You would have to ensure the drill bit was perpendicular to the hole at the same time ensuring no metal enters the crankcases and you don't drill too far. Not for the fainthearted by any means, I certainly wouldn't fancy it myself. To be completely honest I can't see any machine shop being willing to attempt it with the engine in situ, but you never know.

Oh the usual pitch of metric fasteners used in the automotive world is 1.25 and stick with the OEM'O' ring . Good luck.
 

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Phil13, Don't forget the Oil dripping out.


If I had an extra plug, I could measure. You might be able to borrow a Thread Restore kit. Its used to repair existing threads. Where a Tap will cut new threads. I have a set of them from Sears (Craftsman) and have saved me some headaches on Lug nuts.
 

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Discussion Starter #7
After tinkering around a bit I decided to tap the oil pan for the helicoil. I used a 1/2-13 set and I'm replacing the plug with that size. I elected not to drill because it wasn't THAT damaged (still sealed, just didn't tighten down all the way) and I didn't want to deal with shavings in the crankcase and all that drama.
 

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Well done, the proof of the pudding will be torquing the new drain plug up to the correct n/m or lb / ft .
As you've gone for a new plug, try a copper washer, or failing that a red fibre washer to seal the plug to the crankcase mating surface.
 

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Discussion Starter #9
As of this afternoon, I'm pleased to report that my new drain plugs arrived and I was able to install one successfully with the helicoil in place. I used a 1/2-13 flange bolt (11/16 head size), a regular metal oil washer, and teflon tape on the threads. Everything sealed up, the bike is now full of oil and runs fine, and so far no leaks so I think all is well! :D
 

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Looking back it was such a small thing (pun intended) that caused sleepless nights and high blood pressure. You have got to love the mechanics of a motorcycle.
 

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Discussion Starter #13
So, I had another leak from the drain plug area. I lost about 1.5 qt over 150 miles of riding. I pulled the plug out today and noticed that the teflon tape I used was...pretty awful. It shredded quite badly when the plug was screwed in, and made a big ole mess, plus some of it seemed to have melted or otherwise created some hard nasty stuff on the washer. I'm thinking it's not a good idea to use it with the helicoil and it may be why I had a leak.

I cleaned all the old tape off, replaced the washer, and reinstalled the plug without the tape. Filled 'er back up with (super cheapo) oil and started it up. Runs fine and doesn't leak a drop while off or at idle. I'm busy this weekend but I'll take it out for a ride on Monday and see how it goes (with a spare quart of oil in my backpack, just in case!).
 

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......I'll take it out for a ride on Monday and see how it goes (with a spare quart of oil in my backpack, just in case!).
Seems like a wise precaution! Hot thin oil will always find a way out if a weakness exists.

Your PTFE tape is being shredded because either the Heli coil hasn't formed a 'clean' thread profile, or when you put a couple of turns of tape around the plug thread you wound it in the 'wrong direction', or possibly both.

With a right hand thread, holding the bolt head towards you and the threaded shank facing away, you need to apply the PTFE tape in an anti clockwise direction around the shank.

If you apply the tape in a clockwise direction, the loose end of the tape is facing the start of the thread and tends to catch on it as you screw in the plug, then the tape gets shredded and obviously doesn't form a 'seal'. This is even more likely to happen if you have torn a length of tape off the reel. Always cut PTFE to length with sharp scissors.

Wrapping the tape anti clockwise ensures that the tape end trails away from the start of the thread and is drawn smoothly into it as you screw the plug home.

I hope that makes sense, because it's a **** sight easier to show someone than explain it!
 
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