I just bought an 09 America 3 weeks ago. I had them install a tach and the tach worked fine for a week. Now the tach gets off by 500 rpms every time I ride. Later I found at the end of each ride, if i hit the kill switch the tach will drop 500 rpm, so when i kill the engine and the tach reads 1000 I hit the kill switch two times to bring it back to zero. has anyone else experianced the same thing?