K/Sportster Case Oil Drain Plug

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K/Sportster Case Oil Drain Plug

Postby wallaman » Wed Dec 06, 2017 9:39 am

Always thought that early K's used the special oil level drain plug and that once a separate level plug was put into the primary cover, the special oil plug was replaced by a standard oil plug/bolt (or at least that's what my parts books say). I was gong through some parts I had in a box on my shelf and found an NOS special oil level drain plug (34745-52) still in its original dealer parts bag. There was also a used one in the same box but it was a good bit shorter (see pic - NOS on right, used on left). The used one doesn't look like it's been shortened (at least it looks like it as a nicely machined end), but I don't think there was an "in between" version. Any thoughts?
Chuck S.
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Re: K/Sportster Case Oil Drain Plug

Postby starcain » Wed Dec 06, 2017 3:44 pm

Chuck, I've been trying to figure this one out for years with no luck. I brought this subject up in an earlier post in the "K,KK,KH,KHK" section under "1952 & 153 K/KK transmission plug". When I was doing my KK many years ago I found that I had 5 transmission drain plugs with two different lengths, 3 long and two short. I had no clue what was correct. Obviously it would make a huge difference in oil level from one to the other. I noticed that the 3 long ones all had damage to the ends of the tube that ended in about the same place on the tube. I had to assume that the long ones had been rubbing up against a gear or something. I ended up using the long one to the far right in the picture because it had the best hex on it and cut it off to the same length as the short ones that I had. None of the short ones showed any signs of wear so I figure that was a safe length. I saved the end I cut off and that's why the far right one in the picture is in two pieces. This spring I drained the transmission and primary oil for the first tine in a long time and found myself wondering again why there is two different lengths? Not knowing for sure which length drain plug gave the correct oil level I put the short one back in and filled with the 1-1/2 pints of oil the riders handbook says to use. After I got the oil filled I removed the small 3720 oil level screw and got almost a half pint of oil back out so if 1-1/2 pints is the correct amount of oil the short plug is not correct. I believe the long one would give you the correct oil level but using a long one just didn't seem like a good idea after seeing the damage on all three long ones I had. The NOS long one in your picture appears to be even longer then my three? I never got any comments or feedback to my post so it's still a mystery to me. Would like to know though if anyone else has dealt with this issue.
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Re: K/Sportster Case Oil Drain Plug

Postby Lisa » Wed Dec 06, 2017 6:20 pm

If it were me I would machine down the end of the long one thin like a straw thickness so it doesn't hit anything and your good to go. My opinion. Simple fix. Guess the super stars at HD couldn't figure it out so they made a short one that wasn't correct for checking oil level sounds good to me ?
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Re: K/Sportster Case Oil Drain Plug

Postby starcain » Wed Dec 06, 2017 8:27 pm

Turning the end down is a great idea and the next time I have the plug out I may do that. I tried a long one just to see if I could feel any resistance as I was going in and couldn't feel anything. Also took a punch the same diameter as the tube and ran it up in there and couldn't feel anything, at least with it in neutral. I didn't try it in different gears. It made me think that maybe it was getting hit as one of the gears moved laterally on the shaft. As much trouble as the early K transmissions were known to have maybe with that long plug in there it was keeping the gears from fully engaging. If, and that's a big if, that were the case it may still rub with the end turned down????? There had to something going on with them for me to have come across three used long ones all with damaged ends. I'm not even sure if the short ones came from the factory that way or if they were shortened by owners. You would think that maybe there would have been a shop dope bulletin on it.
Stan
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Re: K/Sportster Case Oil Drain Plug

Postby Lisa » Wed Dec 06, 2017 8:59 pm

Turn it down paint it on the end and run it then check to see if it rubbed on anything ? simple to find out - or raise the rear wheel pull in the clutch and rotate the back wheel through all the gears then remove the plug and inspect it to see if it rubbed on anything ?
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Re: K/Sportster Case Oil Drain Plug

Postby EKHKHK56 » Thu Dec 07, 2017 4:20 am

H-D didn't leave too much to chance. The longer and shorter versions may be -52 or -54 which have different capacity Clutch Covers. To maintain same oil amount the level would be lowered in the -54 larger capacity cover. My guess. Erik K
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Re: K/Sportster Case Oil Drain Plug

Postby ambike » Thu Dec 07, 2017 6:52 am

Polishing the chew marks off those things is a good job for a Dremel.

Yep, finding good help in and out of local high school vocation shops was a crap-shoot.
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Re: K/Sportster Case Oil Drain Plug

Postby starcain » Thu Dec 07, 2017 7:12 am

EKHKHK56 wrote:H-D didn't leave too much to chance. The longer and shorter versions may be -52 or -54 which have different capacity Clutch Covers. To maintain same oil amount the level would be lowered in the -54 larger capacity cover. My guess. Erik K


In 1954 they came out with the 34951-54 primary cover that had the oil level plug in it so the early drain plug with oil level tube was no longer needed. It's a '52 or '53 part only.
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Re: K/Sportster Case Oil Drain Plug

Postby wallaman » Thu Dec 07, 2017 9:53 am

Interesting. I had a '52K some years back and my recollection is that it had a "long" drain plug like the one in the first pic I posted. If you look carefully at it, the last 3/8" -1/2" or so is tapered. It is also interesting that the short one I have is approx 1 3/8" long like the two in the second post. Coincidence? Not sure where the other three in that pic come into play at 1 3/4". My NOS one is approximately 2". I only see one part number in all of the parts books that I have (-52). Were there actually two or three versions of the part from the factory and they just didn't update the part number? A Shop Dope fix? As Starcain noted, the -54 primary cover eliminated the need for the "level" function of the drain plug as the cover had a drain hole in it to set the level. '54 on show a "standard" solid drain plug for the bottom of the trans. Curiouser and curiouser...
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Re: K/Sportster Case Oil Drain Plug

Postby starcain » Thu Dec 07, 2017 11:14 am

wallaman wrote:Interesting. I had a '52K some years back and my recollection is that it had a "long" drain plug like the one in the first pic I posted. If you look carefully at it, the last 3/8" -1/2" or so is tapered. It is also interesting that the short one I have is approx 1 3/8" long like the two in the second post. Coincidence? Not sure where the other three in that pic come into play at 1 3/4". My NOS one is approximately 2". I only see one part number in all of the parts books that I have (-52). Were there actually two or three versions of the part from the factory and they just didn't update the part number? A Shop Dope fix? As Starcain noted, the -54 primary cover eliminated the need for the "level" function of the drain plug as the cover had a drain hole in it to set the level. '54 on show a "standard" solid drain plug for the bottom of the trans. Curiouser and curiouser...


Chuck, Wow thanks for pointing out the taper on your long one. I didn't notice that the first time around. That is very interesting. I bought the KK back in 1984 and can't remember what style drain plug originally came with it. All the ones in my picture were purchased through the years at swap meets with exception of one that may have been what came with the bike. Of course I don't remember which one. Anyway, I don't know the back story on any of them. The fact that your long one is tapered on the end tells me that at least at some point they realized they had a problem with the originals. Any chance you could measure with calipers or mics the tube diameter and the smallest part of the taper to get an idea of the difference. And maybe at what point of the tube it starts to taper and the exact length of the overall tube from the bottom mating surface of the hex. Would be great to find a shop dope bulletin on it. Maybe it wasn't a big enough deal to warrant a bulletin and they just started making the tapered ones as replacements?
Stan
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