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95 touring bike. leaking bad at primary and on the guess is the mainshaft seal. now my service manual showes an oil seal being installed on the shaft without removing the sprocket. could this be the bad seal or is it behind the sprocket. thanks jesse coats

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More likely trans seal or inner primary seal and may as well change the starter seal while you got it open im not sure what seal you speak of but you got a lot of tear down in front of you and youll need a special socket for the trans pulley

Posted on Feb 11, 2010


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I have leak from what seems to be from behind the primary case.

sometimes the mainshaft leaks.. ****** ..or I have seen where shifter exits the ****** behind the primary that seal leaks ,, look under & from above ..anyway youll pull the fix good luck..check out our info at

Aug 16, 2011 | 2000 Harley Davidson FLSTC Heritage...

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Do 2007 touring models have inner primary seal leaks

Any machine that has oil in any gear case is subject to have oil leaks. The '07 touring models are no exception. There are several seals in that area and the possibility of a leak always exists but if you're asking if the 07 models are more suseptable to the leaks, the answer is no. In the early 1990's, they did have a problem with the front belt pulley wearing and getting loose. Then, the "quad seal" behind the pulley spacer would allow transmisison oil to seep out in the transmission final drive gear splines.

Good Luck

Aug 09, 2011 | Harley Davidson FLHRS - FLHRSI Road King...

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Inner primary seal keeps leaking replaced three times all other seals replaced to rode another 1200 kms leaking out inner primary seal still which brand off equitment do you reccommend to use or why is it...

There are several places that could be leaking in this area. First let's talk about the seal that goes in the backside of the inner primary. I always use the James double lipped seal in this area. When you install the seal, put some sealant on the outside circumference of the seal. It must be installed to just below the surface of the primary and it must be straight. Before putting the inner primary back on, lubricate the inner bore of the seal as well as the surface the seal is going to seal against. If the engine starts up and seal has no lubrication on it, the friction will burn the delicate sealing lips and they will be damaged. Your leak could also be the large seal in the face of the transmission behind the front belt pulley. Everything I just said about the inner primary seal applies to this seal as well. The last thing is the pulley could be worn in the spline area in the center of the pulley. You didn't say what year model your bike was but over time, these splines wear and the pulley becomes loose. When this happens, the tension on the "quad seal" behind the spacer on the transmission main shaft fails. Transmission lubricant seeps down between the mainshaft and the spacer and out of the splined area of the front belt pulley. Take the lock plate off the front pulley and check to see if the large nut is tight. If it isn't tight, this could be the problem. The large nut has LEFT HANDED THREADS. Retorque the nut to 150 Foot Pounds. You'll need a special socket and sprocket locking tool to do this job. Take the pulley off and check the splines and replace the quad seal. Make sure you check all the areas whenever you have the inner primary off.

Jul 17, 2011 | Harley Davidson FXDL Dyna Low Rider...

1 Answer

Just changed primary gaskets and all seals on this side i have oil dripping never been in gear just started up could it be crank breather problem

Did you change the seals behind the front belt drive pulley? The front pulley is made of cast iron and the final drive gear is made of hardened steel. It's specifically made this way so that the pulley wears instead of the expensive and difficult to replace final drive gear. When the splines in the pulley wear, the pulley loosens up and the tension on the "quad" seal behind the spacer is lost. This allows transmission oil to run down the splines of the final drive gear. Check the oil level in your transmission and see if it's low. When you start the engine or ride the bike, it'll leak a spot about the size of a half dollar. If you wipe that up, it will not leak anymore unless you start the engine or ride the bike. You'll have to pull the front pulley off to check the splines for wear. If they are worn, Harley makes a kit to repair this with.

Now, it could still be the seal in the backside of the primary. A lot of people make the mistake of putting this seal in and assembling the primary with the seal left dry. When the engine starts, the mainshaft starts to turn and the friction burns the lip of the seal up before oil can get to it. The seal is destroyed in the first ten seconds or shorter. When you replace the seal, always put a gasket sealer around the outside of the seal and put some oil or light grease on the lips of the seal before you assemble it.

It's not your crankcase breather as that is at the top of the heads. The two large bolts that hold the air filter backing plate on are hollow and the crankcase breathes through these bolts into the air cleaner.

Good Luck

Apr 02, 2011 | 2003 Harley Davidson FXDWG Dyna Wide Glide

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Thanks wd4ity, your instructions helped. I checked everything. But after changing 4 seals of different makes, its still leaking after a quick run round the block. The leak is not as bad but get a small...

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

Jan 18, 2011 | 2004 Harley Davidson FXSTD - FXSTDI...

1 Answer

I have a 2004 Duece FXSTD. Drops of oil was found on the floor under clutch area of the primary. After some inspection, I found that it was streaming from the inner primary.Got a seal set from Motor...

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

Dec 27, 2010 | 2004 Harley Davidson FXSTD - FXSTDI...

1 Answer

Leaking primary

If the primary is leaking on the backside, you must pull the entire primary drive to gain access to the backside.

Start by draining the primary. Disconnect the battery, remove the outer primary cover, jackshaft for the starter, the engine sprocket nut, remove the circlip and remove the clutch rod adjuster, remove the mainshaft nut to get the clutch off (left-handed threads), primary chain adjuster.

From the right side of the bike, remove the exhaust system to gain access to the starter. Remove the starter.

Go back to the left side and remove the bolts that secure the inner primary to the engine and transmission. Once you have all the bolts out, the primary cover should come off easily. If it doesn't, look for a bolt that you may have missed including on the backside.

Now that you have the inner primary cover off, you can replace the seal on the backside of the cover. Install the seal but before you put the cover back on, you must lubricate the inner lips of the seal where it rides on the mainshaft. Many people don't do this and they destroy the seal in the first five seconds of running. Without lubrication, the mainshaft turns so fast that friction will build up heat and damage the seal within the first few seconds of operation before oil can get to the seal. Lubricate that seal.

Now , Since you've got the inner primary off, there are some seals in the transmission that should be replaced as well. I always replace every seal back there everytime I go into that area. Replace the large final drive gear seal as the thin seal between the mainshaft and the final drive gear. I also replace the Quad Seal behind the spacer behind the belt pulley. This will require the special tools necessary to remove the pulley. If you have those, I'd recommend doing this job as well.

As you can see, this is not a job for the faint of heart. It's a complicated job and a lenthy job. This is why the dealer charges so much to do the job. Now, my experience on doing this job is on the earlier Evo and Shovelhead models but the Twin Cam can't be that much different. I'll help as much as I can via this medium but I must recommend that you purchase a service manual. This medium does have it's limitations.

Good Luck

Aug 05, 2010 | 2001 Harley Davidson FLHRCI Road King...

1 Answer

How to replace inner primary seal

Replacing the inner primary seal is a major job. You must remove all the primary drive components such as the primary chain and the clutch assembly. Then the exhaust system so you can get to the starter to remove it. Then you must remove the inner primary itself from the engne and the transmission. The seal is on the backside of the inner primary. If you replace the seal, remember to lubricate the lips of the seal as well as the mainshaft before you reinstall the inner primary. If you install the seal dry, when you start the engine the mainshaft will burn up the seal in about three seconds before the oil gets to the seal. Put some oil on that seal.

Now, once you're in there, you may find that it isn't your inner primary leaking at all. It could be a transmission seal. One of the worst culprits is the Quad Seal behind the spacer that is behind the front belt pulley. You'll need some special tools to remove the pulley and replace this seal if it's leaking. It looks like a standard O-ring but it isn't. Both the compensator sprocket nut and the front pulley nut require a LOT of torque. The compensator nut takes 150-165 foot pounds and the front pulley nut takes 150 foot pounds. Also, the mainshaft nut that holds the clutch assembly on takes 60-80 foot pounds of torque LEFT-HANDED. You will need a way to lock the front pulley and the primary chain in order to apply these levels of torque to the required fasteners.

This is a complicated job. That's why Harley charges so much to do it. I would suggest that you purchase a service manual as there is far too much involved in this job for me to type it in step by step here.

Good Luck

Aug 05, 2010 | Harley Davidson FXDWG - FXDWGI Dyna Wide...

1 Answer

Oil leak -between inner primary and transmission . Changed broken belt and now I have this leak. I put new mainshaft seal and jackshaft seal. Help!!!

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

Jul 13, 2010 | 2000 Harley Davidson FLHR-FLHRI Road king

1 Answer

Oil leaking from the back of primary case

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.

Apr 22, 2010 | 2004 Harley Davidson FLTRI Road Glide

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