GSX1100F Tacho being weird

[Brians 7/12]

Hi… just bought a Powerscreen for the engine/carbs/oil cooler/loom etc… but whilst riding the bike the tacho revs pass the redline until it can’t go any further… if it had numbers there it would probably read 16,000rpms… lol 

basically just doing 70mph in 5th & the revs are off the counter when should probably be showing around 6k !? 
 

any ideas what to check please 

[Gixer1460]

Someone rewired it and connected both coils instead of just single tach source? Other than that its FUBAR'd