I have this tidy little digital speedo stuck to my dash witch has a top speed recall button, Its called an ULTRA speedmeter No.4000 it also has a button for trip, for 0-400, and one for pulse. fitted at stillway in japan, Thing is it reads fine to about 220 but at speeds around 230+ it can jump 10 to 20 k ie: 222,223,224,225, 245.?????