Dyno'd the bike yesterday,,,found the tach off by 400 rpm's,,,

1400 is actually 1000 rpm's,,,,,,,
It has no problems with back-fire or front fire at 1000 rpm.
Is there a way to re-calibrate my tach???
I did not notice anything external for adjustments.
thanks,,,les
Will be posting Dyno results(2007 America Dyno Results) and need help
