I need to adjust the TPS on my son's 03 YZ450. Manual indicates that the engine RPM needs to be 1,900 - 2,100 rpm. At the moment I don't have have an inductive tachometer, so the question is how important is it to be spot on or can I get it close by ear? Also, since I really should buy a tach, anyone have a recommendation? Since this doesn't really have a traditional plug wire I am little confused as to what I should be looking for.....?