Could be a million things ……you’ll have to start diagnosing the issue,……if the tach sensor looks to be ok, ( correct gap, etc. ) start looking at mechanical binding issues, traction tire hanging up on a brake arm, rods and valve gear colliding with things, ….lots of stuff to look at…..take the shell back off, and rotate flywheel by hand, noting any spots that bind. If you find a spot that binds, look for the obvious first, then move on to more complex diags ……..I’ve seen the cross head guides on GS’s squeezed in just enough from shipping & handling to rub a crank bolt and cause a drag every time it went by, …..that’s just one scenario…..you’ve got a little bit of investigation to do,…..if all seems fine, you might want an ASC to take a look at it,…
Pat
