I secured an old Airguide tach off e-bay. the seller said it was for a 2 cyl. 2 stroke. I hooked it up to the kill switch wire, but it reads 3000rpm at idle? What does this 2 lead tach connect to? On the face it says for models 653 or 654. In yellow paint on the back, it says 9FA. A little help please? Thanks, Joe.