I think my seals on my final drive system are leaking. How do i find out?

I assume the leak is where you replaced the seals, so I would assume there was enough ware that even with new seals, they aren't sealing completely. You can drive around and see if the seals finally seal, but if the leak is at the water pump, I would consider just getting a new water pump and installing it.

Ok, usually when I give information on things like that, I tell them everything that I know so that they get their problem fixed the first time. I don't allot it out piece at a time. So, undoubtedly, there is something amiss here, not just the normal leaky seal.

If you are positive that the leak in coming from the backside of the inner primary at the mainshaft. There is a starter seal up just a bit higher that can leak as well. You should have already checked the inner bearing race position on the mainshaft, 0.100" from the face of the final drive gear and that the race is between 0.9950" and 1.000" (25.27-25.40mm) long. The race is free of burrs and deep scratches. The new seal should have a tension of about 0.5mm (0.020") between the seal and the bearing race. If you measure the inside of the seal with a caliper and then measure the outside of the race, the race should be a bit larger than the seal.

When you installed the seal, did you inspect the recess where the seal goes in to make sure there are no cracks? Did you use the sealer on the outer edge of the seal ( I like non-hardening Permatex) and lubricate the seal where the bearing race runs with Lubriplate or oil. When you install the seal, make sure the lip of the seal where the bearing race runs is pointed INWARDS towards the clutch, not the trransmission. The "Lip" of the seal always faces against the direction of oil flow and is seated about 0.050" below the surface of the backside of the primary. The seal must be straight as well. If you get it in crooked in won't seal. If you can't get an OEM seal, try to order a James Gaskets seal.

Double sealing does no good as no oil gets to the outer seal and it burns up very quickly even if you pack grease between the seals. This used to be used on the old Shovelhead with the sealed bearing. It does keep dirt away from the seal though.

Now, it still sounds to me like it's your quad seal behind the front drive pulle. The quad seal keeps the transmission lubricant from running underneath the spacer behind the front pulley and then down between the front pulley splines and the final drive gear. When it drips off, it will drip onto the mainshaft and run down the backside of the inner primary.

Next time you have the inner primary off, take the lock plate off the front pulley and check the large nut. If it's loose, this could be your problem. Usually the nut is loose enough to turn it by hand. It has left handed threads in the nut. The front pulley is made of cast iron and is softer than the final drive gear. This is by design so that the relatively simple and cheap to replace front pulley wears instead of the expensive final drive gear. Without taking the final drive belt off, you probably won't feel any movement in the front pulley.

Well, I hope this helps again. For the life of me, that's all I can thnk about. I've even included some information that I never check in most cases, like the length of the inner race.

Good Luck and Ride Safe
Steve

The first thing to do is determine if the oil is motor oil or gear oil. If the oil is leaking from the final drive end( gear oil ) it will have to be removed and inspected for bearing wear and have the seal replaced. If the oil is leaking from the motor and then running down the swingarm, the final drive and swingarm will have to be removed to replace the output shaft seal.
Thanks and I hope that this helps.
Steve

Did you check your front belt pulley? These pulleys are made of relatively soft cast iron as compared to the final drive gear. This is so that the easily replaced and relatively inexpensive front pulley wears before the difficult to replace and expensive final drive gear wears. The pulley will wear in the splined inner bore and will get loose on the final drive gear. Then transmission oil will run out of the pulley and down the inner primary. This is because of the lose of pressure on the "Quad" ring behind the pulley spacer. This may be your problem.

Another mistake a LOT of people make when replacing any seal is putting the seal up dry. On the inner primary seal, you want to put a bit sealer compound around the outer edge of the seal where it goes into the case. Although there are a lot new sealants out there, I still prefer good Permatex non-hardening. Once you get the seal in and straight, oil the inner seal surfaces and the bearing race. If you put the seal up dry, you start the engine, the mainshaft turns about 1000 rpm. This will burn up the delicate rubber lips on the seal almost instantly because of friction before the oil can get to the seal. You MUST lubricate the seal or it WILL burn up before you can blink an eye.

Also check the position of the inner primary bearing race. It must be 0.100" from the final drive gear. If it's way out of position, the seal may not be riding properly on it.

If you are in doubt about whether the transmission is leaking or the primary, refill the primary with a quart of automatic transmission fluid, the red stuff. It will work long enough for you to determine whether it's the transmission leaking or the primary leaking. If it's the transmission, check the front belt drive pulley for wear, You'll usually find that the large nut that holds it on is loose.

Good Luck
Steve

Depending on which side is leaking, it could indicate a simple seal replacement or something more serious like a failing bearing.

Leaking on RHS, is probably just a seal replacement. Leaking on LHS by the brake rotor and wheel may indicate a bearing about to fail. Put bike on center stand and get down beside the wheel. Hold wheel (with trans. in neutral) at 12 and 6 O'clock position try to move wheel by pulling and pushing towards yourself and away from yourself. There should be a barely discernable amount of play in the final drive bearing. Now, rotate wheel and feel/listen for grinding or other vibration that might indicate a bearing problem. If you have mechanical skills, you can drain the oil from the final drive an check for excessive metal particles.

Let us know what you find out!

Clean everything off the best you can with old cotton cloths. Run the car for half an hour to get oil nice and hot and under pressure. When you stop the car and leave to cool if the oil leak is bad a tell tale drip of oil will be located to the site of the problem. If the leak is the main pinion seal on the transmission this is not such a big job. Put a dab of light paint or Tippex correction fluid across the universal coupling so that you can put it back together in the same pattern. Drain the transmission oil into a clean plastic tray, if it red and clear you can re-use it. If brown and opaque just replace it. Take the prop shaft coupling apart and withdraw the splined drive from the tail of the transmission. The old seal can be levered out with the aid of a screw driver. Fit the new seal using a a large socket as load spreader and a hammer to help tap it into position. Lube the oil seal face and reinsert the splined drive. Refit the prop coupling and refill the transmission via the transmission dipstick. Check the fluid level with engine running and transmission in park. If the seal is found to leak afterwards this may indicate a problem with the pinion bearing allowing the final drive too much play and breaking contact with the pinion oil seal. If this happens take the transmission to a transmission specialist who will be able to advise on whether it is best to rebuild or replace it.

While it is not difficult to replace the seal, this usually indicates that the main bearing in the final drive has failed and pushed out/damaged the seal causing the leak.

Put bike on center stand and hold rear wheel with both hands and 12 and 6 O'clock positions. Try to move wheel by pushing towards the side of the bike in each direction. If wheel moves more than 1-2mm then you need to have final drive repaired. You can also remove drain plug at the bottom of the final drive and see if any metal particles drain out with the oil. Use a small drain pan to catch the oil.

Sorry, but likely not an easy seal replacement to fix this problem.

There are several seals that can leak in this area. You say you replaced the mainshaft seal in the back of the primary. I've seen a lot of people replace this seal only to have it start leaking immediately. The reason was that they didn't know you must lubricate the seal before you reinstall the primary cover. When you put the primary cover on with the seal dry, when the engine starts up, the mainshaft immediately goes to 1000 RPM or higher with no lubrication on the seal. The friction burns the lip of the seal up before the lubrication in the primary can get there. It only take a second, literally.

Other seals that can cause leaks in this area are the large final drive gear seal in the face of the transmission behind the front belt pulley and the "Quad" seal that is inside the transmission. The Quad seal is almost like an O-ring. It's purpose is to prevent transmission lubricant from seeping out through the splines of the final drive gear. If the front sprocket splines wear and the sprocket gets the slightest bit loose, the compression on the Quad seal will be lost and the tranny will leak. The tale tell sign on this leak is that the transmission will leak a spot of oil about the size of a quarter or a bit bigger when you park the bike. If you wipe up the spot, it won't leak anymore until you either ride the bike or simply start the engine. Then it'll leak that quarter sized spot and stop. Check your lube level in your transmission.

Whenever I pull the inner primary and the belt on a Big Twin, I replace ALL the seals. Make sure you lubricate the lips on the seals so they don't cook before lubrication can get to the seal.

Good Luck
Steve

There are several things behind the inner primary case that could be leaking. There is a seal behind the inner primary where the transmission mainshaft goes into the primary. This seal sometimes starts to leak. Also, there are seals in the transmission in that area. The final drive gear seal is the big seal right behind the front final drive belt pulley. Somethimes this pulley wears on the splines of the final drive gear and it loses tension on the "quad seal" on the final drive gearshaft.

You'll nee some special tools to get to this area. You'll need sockets to fit the compensator sprocket nut and the clucth nut. You'll need an airwrench, a primary locking bar, and a torque wrench that will pull 150-165 ft. lbs. torque in forward direction, 68-80 ft. lbs. LEFT-HANDED on the clutch nut, a primary locking bar, a final drive sprocket locking device, a mainshaft nut removal tool, and some seal pullers and installers. Good Luck.

you have a damaged seal replace it and you should be just fine