74 750 GT Kickstarter Shaft Seal renewal

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Tom Willis
Cucciolo - the Lil Pup
Posts: 9
Joined: Tue Jan 03, 2006 3:57 pm
Location: Palestine, Texas

74 750 GT Kickstarter Shaft Seal renewal

Post by Tom Willis » Fri Jan 06, 2006 12:31 pm

First, order a 20mm x 26mm x 4mm oil seal (Chicago Rawhide 7854) from Pervis Bearing. I think the seal was $4.00 and the shipping was $6.00. Still, cheaper than you could order it from Ducati if they even had one! Then buy a small package of 4x3/8 flat Phillips head screws from Lowes. You will probably need more than one screw. Next find a ½”x 4” long XXH (schedule 160) threaded pipe nipple. You can use something else like it but this is what I had available. In the Oil Field we call this a hydraulic nipple. You will also need Safety Pliers and some .032” safety wire.

The factory manual only makes reference to replacing this seal when you have the cases split. Since I wasn’t about to try that, I decided I would have to do it from the outside. I removed the alternator cover and the shifting cover. Because the seal is 2” deep inside the cases and because there is very little working room around the seal, it looks almost impossible to get to the thin (3mm thick) seal. It is not easy but here is how I did it.

This seal like all seals is press fit into the case so it cannot be pried or “pulled” out. I tried this but it only tears the rubber lip around the seal. Great, now I have to get the seal out as I have ruined it! A quick call to a real mechanic, Ray Donaldson, in Dallas and I find out it must be “popped” out (like a dent puller used in body work) not pulled. I knew that! Secondly I found out through trial and error that the screw must go in straight so it bites into the metal rim around the seal. That means you must reduce the size of the head of the screw so it does not angle towards the center of the shaft when you screw it into the seal. Put two pieces of wood in a vise and insert the screw between them to file the head down. I use mylar pieces that I use to clamp shafts and such to prevent damage while clamping. File the screw head down in a clockwise direction (so it doesn’t loosen) until you get to the edge of the Phillips head slots as seen in the photo. While still clamped twist the safety wire round the screw and bend the wire 90 degrees at the screw head (see photo http://xs.to/xs.php?h=xs62&d=06015&f=IMG_1210.JPG). Cut enough wire to clear the 2” of case, install the hydraulic nipple and have enough room to slide the nipple when hammering against the safety wire pliers clamped on the end of the wire (see second photo http://xs.to/xs.php?h=xs62&d=06015&f=IMG_1212.JPG). You could also use Vise Grip pliers for all of this instead of safety wire pliers.

Now we are ready to screw to screw into the seal. Start the point of the screw close to the outside of the seal using a small Phillips head screwdriver. This will help the screw threads “bite” into the metal ring on the outside of the seal. Position the wire loop on the outside of the seal to make it bite better. Now slide the hydraulic nipple out hard against the pliers to “pop” the seal out. It may take a couple of screws inserted into different places on the seal to get it out. I put the first one in at 3 o’clock and the second one at about 5 o’clock. The seal popped out on the second screw and almost slid all the way off the shaft! Take time now to say a little thank you prayer and jump up and down a couple of times before you run next door to the neighbors to brag about what a great mechanic you are. It only took me about a month of stressing out to get to this point!

To install the seal, tape the splines on the shaft with one layer of masking tape to prevent any damage to seal when sliding it over the shaft. I used a piece of shower rod to tap the seal in as there is not much clearance on the top and bottom. Tap it a couple of times and check the seal to make sure it is going in even on all sides. I had to use a punch to finish getting the seal flush with the case as it didn’t want to go completely in at the 4 o’clock position.

I hope this helps someone. If you have any questions feel free to email Tom Willis at bmwr90s76@hotmail.com and I will try to answer any questions.

Mach 3
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Location: Florida, USA

Post by Den » Thu Jan 19, 2006 8:14 pm

Even though you mucked up the old one, I believe there's still enough room to fit 6 or 7 more seals in that hollow space right on top of the old seal.

Cucciolo - the Lil Pup
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Post by Den. » Wed Dec 03, 2014 9:43 am

Den wrote:Even though you mucked up the old one, I believe there's still enough room to fit 6 or 7 more seals in that hollow space right on top of the old seal.
Upon closer examination it is apparent that there is no support to the OD for more than one seal. So, stacking more won't work.


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