Vibration at 2100 RPM

[Jac Mac]

Ive seen cases where a crank with a crack in the web will vibrate like that under load, but still drive etc due to the shape of the crack, even the oil pressure still seems normal until the crack really gets bad, not likely & hope thats not the case here, but worth keeping in mind..

[DanEC]

I believe that a balancer on an internal-neutral balanced engine is there only to minimize harmonic type forces in the crankshaft. So, unless it is coming apart or the ring has shifter substantially, it's pretty unlikely it's causing an engine vibration problem. I think I would be looking at a problem in the original balance work, the flywheel/clutch assembly or a bad cylinder from a plug or wire.