Re: How do I install tell tail on '87 force 125
Simple--The threaded sending unit screws in the top of the head, just remove the stainless plug (easier said than done) or drill and tap another hole close by (1/16 NPT). Use the orange wire on the sender instead of on the overheat indicator. If you want to keep the overheat indicator, then just run a separate wire from the temp sensor to the gauge.
On your engine, Purple is reserved for tachometer. If you do not have a tach and do not intend to buy one (foolish in my opinion) then disconnect the purple from the rectifier and use it rather than running a separate wire forward.
All other instructions come with the gauge and are self explanatory.