It depends on whether the crankshaft snout is worn or not. Sometimes the balancer hub cracks at the keyway and loses its press fit. That's a pretty quick fix, just install another balancer. If that one has been running with a loose balancer for a while, it can have a worn crankshaft snout that won't let a new balancer press on tight enough to stay put, or the keyway in the crankshaft can be worn to the point that the balancer will move slightly from the torsional strains of running. A worn snout diameter and/or a damaged keyway will require the crankshaft to be removed and welded, then re-machined to the correct dimensions. I have done a temporary repair by brazing the key to the crankshaft, but it's not a good long-term fix. I'd suggest pulling the balancer and doing a thorough inspection, including taking measurements with a micrometer or a dial caliper to find out where the worn areas are, before committing to buy the engine.

I have a drill and tap guide available for use by members of the forum to install a center bolt in the crank snout. I get a small deposit plus a shipping/handling charge but it's basically a break-even situation. It won't fix worn keyways, etc., but it will allow the balancer to be bolted on solidly.
Jerry

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