Recently when I turn my bike on the Tachometer doesn't seem to turn on with the bike, it takes about 10 ~ 20 seconds before the fuel gauge and rpm meter come to life.

Anyone know what may be causing this?

I believe that you have posted on the pre-gen section.

Your problem may be related to the CDI or a weak battery.

Check the voltage of your battery; it should be above 12.6 volts before start ups.