The tach will not go above 4k rpms, and when I really get on it, it gets stuck, I have to tap it real hard with my finger to get it to come back down…
I’ve had mine apart several times to fix the same type of problem. In my case, the needle would stick right around 2300 rpm. Turned out to be just some dust that was causing it. Be warned, though, these things are extremely fragile and you might only make things worse by taking it apart. Besides, what are you doing at 4K rpm anyway? 
I took mine to a friend that is a watch maker/repair. He cleaned it up for me and works smooth now. Find your local jeweler that you can trust and have them look at it.
Check out Bob’s website: http://www.rccinnovations.com/
I haven’t bought anything from him yet, but I would like to in the near future. I am sure some members here can provide more information reguarding Bob and his upgrades.
Paul
Yup, Bob(TheRktmn) has way-cool products…I don’t have an XR7, so I picked up one of his mini-tachs for the clock delete…very cool.
Rocketman is fantastic. Service is first rate, timing is impeccable and he stands behind ALL of his stuff.
I have one of if not THE first 6K RPM XR-7 tach. Has worked flawlessly since the day I installed it about 6 or so years ago.
Thanks guys, I am terrified about tearing into it, I only get above 4000 rpm’s in the first three gears anyway… they usually give up by then.