bhai sahab kion apna aap ko confuse kar raha ho,,
in your 70 there is no RPM meter,, there is just speedometer ,,to tell u the speed and odometer to give u covered mileage,,
so u cannot safely say from speedometer what rpm is it now,,
aso u have to look att the throttle(race) ,,
if u rotate it half of its max rotation u achieved half of its RPM in that particular gear ,,
let me say it in simple terms,, if u rotate the throttle(race) half and u r in first gear u achieved half rpm,,and so on using the how much u rotate the throtte u can tell how much pm u r,,,again its not a very precise rpm measurement but fairly coorrect for ur case,