After a short stop of about 10 mins my tach started reading low, I was near the end of my 240 mile trip. Usually at 60 mph the tach will read around 4300 rpm. Well after this stop 60 was about 3400 rpm. It did this for about 15 miles and the went to normal after a really slow sharp turn. What do I need to check to cure this or no cure for it at all. thanks