tachometer only rev up to 3000 max and engine rebuilt twice and still leaking under the spark plug

[prinquia]

i have a 1977 xs 650 and the tachometer is only reving up to 3000 no more, engine is running well.i just bought a new 650 tachometer and i have the same issue, the drive is working, cable is new,and the rev tacho too, but still not reading the rev properly?
another issue is the engine is running great but is leaking where the head gasket is just under the spark plugs , it has been rebuilt twice with the same issue, retorque properly but still not dry, any advice? wich brand of gasket is the best for 650 xs
thank you for your help

 

[WideAWAKE]

Can you stick a drill on your tach and get it to rev past 3k?

Does your cable move freely?

The head leak… is your head flat??

Seems and if it’s been rebuilt twice with the same issue something may be up with the head itself.

 

[jpdevol]

Oil leaks like to travel....perhaps it's not the head gasket, but a cam seal. Check under the cam covers for residual oil too.

Specs on head flatness: