Tachometer tweak out?

[Monkeyinmypants]

Howdy all, I have a 1980 Yamaha XS100, and one day as I was warming it up, I just happned to notice the tach toping out. As I goosed it, the tach needle,(for whatever reason) just stops at 3000RPM. What happned? Totally accurate up to 3g's, but it acts like there is a peg stopping it or something... Anybody else have similar experience? Tried to dissasemble, but was fairly sealed unit. Any clues?

[Dragonrider]

Often, especially if it has spent some time in the sun . . . the needle or glass has warped and they are contacting. You can see it if you get down and kind of look into is from a steep angle, nearly sideways.

To get it apart you have to dremel the ridge off the bezel ring . . . and put it back on with sealer if you can fix the insides.

[strom]

I started mine after a carb repair kit, gas tank stuff and new head gasket, new fusebox, carb float level set to stock, stock air filter...

So...

The float levels were waaaay lower previously (bout 20-22, now bout 26 mm...forgot), but there was a pretty much open exhaust system, and air filter or the lack thereof.

There is some backfiring from the exhaust, but the carbs are all... well... the word set up is still far away, so I don't worry bout that.

When I revved it a bit, when shutting the throttle and the RPMs fell, the tacho fell to zero, till I gave it some more gas.

Any ideas?

LP