RestoCycle How-To: Replace an engine oil seal

[NobleHops]

Moving over some content I created on Facebook for safer keeping here. This one may seem elementary to many of you.

A mini-tutorial on how to install a shifter shaft seal into a Honda CBX - but the techniques will work for most any old motorcycle.

OK, here's our patient, a 42 year-old shifter shaft seal from our 1980 Honda CBX project. It's not leaking, but quite a lot of the rubber parts on this bike were hard and punky, and it's just a good idea to replace this while the engine is empty of oil and easy to access.

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This is everything we may need, plus a few drops of clean motor oil.

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This is how we'll extract this seal, with this wimpy-looking pick. This particular seal is not metal-reinforced, and that makes removal and installation easy. Once in a while, a stubborn seal will require more drastic measures to get a grip on it to remove, including driving a wood screw into it, and then yanking it out by the screw with pliers. You have to be very careful not to damage the seal pocket, whatever method you use. This is pretty safe, but even so, we're going to take care not to scratch the aluminum seal pocket with the steel pick.

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Stab it dead center of the rubber part, being mindful of where the tip of the pick will end up. What you do NOT want to do is gouge the soft aluminum of the seal pocket with your sharp pointy steel tool.

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[NobleHops]

Clean out the pocket with a RestoSwab™. We mostly want to ensure we don't leave any gritty dust that might interfere with the seal, plus a clean surface that the rubber can seal against. I like a little denatured alcohol on a swab to finish up, to get it super tidy, and it dries with no residue

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Looking good, ready for installation.

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This is me being super careful. This particular shifter shaft is constructed with a shoulder, the splines are a smaller diameter than the shaft where the seal lives. Many are not, the splines are smushed into the shaft and the seal has to get dragged over those splines to install it. SOHC Hondas are a good example, and the shafts are much longer. Clean and deburr those shafts really well before you push a seal down that shaft, and wrap it with electrical tape, lightly oiled. This will ease installation, safely.

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I like a light smear of whatever lube the seal is holding back to ease installation and keep the rubber from wrinkling on installation.

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This seal is rubber and not metal reinforced like what we removed, and so it is pretty easily installed with your thumbs. Work it carefully over the tape and down the shaft and press it in evenly with your thumbs. Presto, almost home, seal is still a little proud.

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[NobleHops]

If you have a stubborn seal that needs to be driven, the tried-and-true is an impact socket, sized carefully to the OD of the seal, and carefully tapped squarely to seat the seal. For longer shafts I have improvised seal drivers out of PVC pipe, cut square and sanded smooth.

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And done. Remove the tape, wipe off any excess oil, see you in another 40 years!

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