I have just bought a 1987 K100RT.  This is my first K100RT and the first bike I have owned for over 20 years! 

I have a couple of issues that I was hoping somebody might be able to advise on. The first was a dead speedo so I replaced the impulse transmitter and all is working again. I also had a oil leak between the oil and water pump housing so I replaced the 'O' ring which solved that issue. The bike now seems to run really well and I have done about 400 miles on it with no issues. The only outstanding thing to sort out is the rev-counter reading too low. At idle it reads below the zero and at 70Mph it reads about 3500. My feeling is that the needle has slipped but I wondered if any one had any thoughts before I start dismantling the display unit. If I do have to take out the display unit, i would also like to replace the gear indicator and clock as these also don't work. Any  guidance on any of these would be greatly appreciated. Thanks.