Tachometer Maintenance

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The tachometer assembly is pretty simple. It uses a worm drive assembly to translate the speed of the engine into a rotation in the tachometer cable, then the gauge assembly converts the rotation of the cable into a display for you to read.

There is a worm gear on the exhaust camshaft which spins a worm (driven gear in the OEM parts fiche) in the valve cover. The worm is connected to the tachometer cable, which then connects to the gauge assembly.

There's not much that can fail with this setup, however it does need to be lubricated and inspected for wear once a year or so. Often, maintenance is neglected on the tachometer cable and the worm gear assembly because it isn't considered important and is easily overlooked. The tachometer gauge can stick, bounce, or not work altogether.

Here's what my old worm and the sleeve for it looked like after I pulled it out of my valve cover.

Old worm and sleeve

Here's a comparison between the new OEM parts I got and the old ones. I highlighted some major wear in the old worm that I noticed. It may be difficult to see in the picture, but I thought it was significant. It's likely original. In addition, it seems that Suzuki has changed the design on the sleeve a bit by making it a single solid piece, eliminating the metal tab.

New and old comparison with wear pointed out

I replaced the seal band and the oil seal. Notice that the seal band is a flattened o-ring (like a rubber band), not a round o-ring. The seal band goes on the outside of the sleeve and the oil seal goes inside the sleeve, facing in the direction shown.

Seal band and oil seal

The tachometer cable screws into the sleeve. The worm fits into the tachometer cable as shown.

Assembled with cable

The worm and sleeve assembly is located at the front of the valve cover.

Worm/Sleeve location in valve cover

You can see how the worm fits inside the valve cover.

Worm inside valve cover

This is the worm gear on the exhaust camshaft that drives the worm in the valve cover.

Worm Gear on camshaft

I used a tiny amount of white lithium grease when installing the worm into the cover.

Grease on worm
Grease on valve cover
Greased worm in valve cover

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