Tools, Parts, and Materials

• Seal Band, Suzuki part number 26451-45000. (This is not an ordinary o-ring - it has a flattened cross-section shape, like a wedding band. Or a rubber band, if you're not married.)
• Oil Seal, part number 09289-05002
• On my bike, the driven gear was worn where the lip of the seal rides, so I replaced it as well. Part number 26431-45002.
• Screwdriver
• Pry bar
• A few dabs of engine oil
• Pick or small tool for removing old seal band without damaging the soft aluminum sleeve.
• Optional: On my bike, the %$#@! tach cable keeps unscrewing itself from the cylinder head fitting. I added a 12mm ID X 2.5mm thick o-ring inside the fitting where the tach cable seats, just to give it something to "squish" against and hopefully give it some vibration resistance. YMMV -- feel free to implement your own creative solution to this problem.
• This would be a great time to lube your tach cable. I use Cable Life cable lube, but a bit of motor oil also works.

Place a rag under your victim -- a tablespoon or so of oil will run out. Remove the retaining screw.

My bike uses a little retainer plate that fits into a notch on the tach cable fitting. On some bikes, the fitting has a tab. The tab is rather fragile, so be careful.

Pry the tach cable fitting out using some creative combination of levers. I used a large screwdriver with a small screwdriver under it as a fulcrum.

The important thing is to apply a bit of force straight out, not sideways. It doesn't take much.

Success will soon be yours!

Sometimes the gear stays in the cylinder head, but there's nothing really holding it in. Just pluck it out with pliers.

Unscrew the fitting from the tach cable, if you haven't already. I left the cable attached so it didn't plop on the floor while both hands were occupied with prying.

Remove the old seal band with a pick.

Using whatever you have lying around that fits loosely, stick it in the back of the fitting, angle it to the side a bit, and push the old seal out.

I used a punch and just shoved the old seal out by hand. You may need to tap it with a hammer.

Coat the new seal with engine oil, then push it into the tach cable fitting with something flat and smooth.

The end with the spring band goes toward the narrow part of the fitting (down in this photo).

You may need to use a hammer on the other end of your pressing tool to tap the seal gently into place.

The seal will end up seated almost flush with the inside of the fitting.

Coat the tach drive gear with oil and assemble it to the fitting.

Coat the narrow part of the fitting and the sealing band lightly with oil and carefully use a pry bar to press the fitting into place on the engine.

Make sure you line up the retaining slot or tab about where it needs to go.

It takes a bit of force to compress the sealing band, but be VERY careful not to put any sideways stress on the fitting.

You may find it easier to remove the tach drive gear from the fitting and place it into the cylinder head first. Either way, you have to be careful to make sure the teeth on the gear mesh with the teeth inside the head before applying force.

Once the fitting is in place, replace the retaining screw, attach the freshly lubed tach cable, and you're done!