HarleyTechTalk

I have noticed large spots of oil coming from the bottom of my 03 ultra primary. I changed out the plug with a new one and changed out the primary gasket with a new one! Didn't see a change. I'm thinking maybe the leak could be from the inner primary gasket? What are your thoughts? Thanks in advance

Most leaks around the rear of the primary will end up dripping off of the drain plug. It could be the mainshaft seal higher up. A really,really thorough cleaning of the back of the cover is required to get rid of previous leak paths. I have "dusted" baby powder in the area. Then using mirrors, lights, etc. hours after a short ride will usually show the source of the leak.

Quote from: chas on November 02, 2023, 02:38:34 AMI have noticed large spots of oil coming from the bottom of my 03 ultra primary. I changed out the plug with a new one and changed out the primary gasket with a new one! Didn't see a change. I'm thinking maybe the leak could be from the inner primary gasket? What are your thoughts? Thanks in advance

Have you noticed which oil is decreasing?
That will tell you if it is the transmission or primary.

Common culprit is the shifter shaft seal (12045). The bushing the shaft rides in isn't a precise fit from the factory, which allows the seal to flex on the shaft, every time you shift. Shine a flashlight between the primary case and the trans case, where the shifter flag attaches to the shifter shaft, to verify.
Good news, it's a $5 part. Bad news, the entire primary has to be removed to replace it. Aftermarket makes a double lip seal (12045DL) that is supposed to help with this.

I agree with Rigidthumper, the shifter shaft seal is very suspect. Ask me how I know.
As far as trying to determine which cavity is losing oil by checking fluid levels, nearly impossible. One ounce of oil leaking on the floor looks like a murder scene. Doubtful it's leaking that much at any one time, and pretty hard to determine an ounce or two missing on a dipstick. No way to check the primary that precisely.

If using something clear or light brown in transmission, put something with some color like Bel-Ray 80w gear saver or Ford ATF in primary and see what color leaks out.
Either way if it's leaking from behind primary, inner primary has to come off. Have a look at transmission mainshaft bearing race that inner primary bearing and seal ride on. Make sure it hasn't walked in towards trans. Should be a little gap

Thanks all for your replies! I have replaced the shifter shaft seal, the main shaft seal, and the main shaft bearing a couple years ago!

Mine leak was the starter seal 

Quote from: chas on November 02, 2023, 02:22:47 PMThanks all for your replies! I have replaced the shifter shaft seal, the main shaft seal, and the main shaft bearing a couple years ago!

Sadly, one of them may be leaking again.

I have replaced hundreds of shifter shaft seals on 5 speeds, a few less on six speeds.   Very common weep source. 

I guess i'll be back in the primary and change out the shifter seal agin!. Is there a better quality seal that is less likely to leak?

There is a double lip seal. Can't remember who makes it.

I think James makes one.

Wasn't there a thread from years back about tightening that area up? My memory ain't that great but a little light came on when i read this.

One source of leaking you haven't mentioned is the 5th gear-mainshaft seal.  That is the seal that goes between the input & optput shafts of the transmission.  It appears in the picture below and is the copper looking seal you see behind the race and it looks like it is just to the inside of the nut attaching the pulley.  I have had two of these go out on me.  One was simply worn out and the other was caused by the race pictured here walking inward and destroying the seal.  In either case that race has to be removed to change this seal and I recommend  replacing it with an S&S tapered race to prevent future walking (I learned the hard way on that one).  If this seal is indeed what is leaking, transmission lube will be coming out.

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Thanks Serx1 for the pic and the tip! I'll check the tranny level to confirm that this could be the leak!

Leaks can be a pain in the A to find. I had a similar issue this fall on my 2002 RK. A quick visual inspection indicated a leaking shifter shaft seal (O-ring). It is recommended by some mechanics that when installing this seal (o-ring) to cover the shaft splines with something like the plastic baggie the seal comes in. This is to protect the 0-ring from being damaged by the splines as it is stretched to go over them and onto the shaft. Did you cover the splines?