Tachometer Wobble

A number of owners reported problems with "tachometer wobble" where the tach fluctuates constantly. When I picked up my current XS Eleven I immediately noticed the wobbling tach and set out to fix the problem. However, the tach on my '79 SF is a sealed unit that is electronically driven (the '78 appears to be the only mechanically driven tach). In partially disassembling the tach I noticed that there are small holes in the bottom of the unit. Since I couldn't get to the mechanism inside directly, I sprayed a silicone lubricant into the tach through the bottom holes and reassembled the unit. The fluctuations disappeared and have not returned.

The electronic tach on my '80 SG wobbles alot. After I sprayed WD-40 in there, it stopped all together. I called a repair shop who informed me that inside there are ball bearings 1/32nd of an inch in diameter. They do tend to get dirty and can foul up the tach. He stated that if you spray WD-40 into an electronic gauge, it must be squirted *exactly* onto the teeny tiny bearings and if you miss at all you will get the WD-40 all over the electronic circuit board and that will mess up (short circuit) everything (as it did on mine). I was told to liberally spray circuit board cleaner (can be purchased at Radio Shack) all over the inside of the gauge. While doing this, hold the gauge upright, so the cleaner does not drip onto the inside of the glass. This action will inturn dissolve all the gunk that has built up inside the gauge and clean the circuit board. I haven't had the time to try this yet but it does seem to make sense.