What caused this?

[YENKO DEUCE REGISTRY]

Thanks for the reply Casey, I ordered an installer tool - no need to use the BFH. I believe the rca is a bolt that lossened up, I don't believe I have an engine balance issue. I had the engine balanced by the machine shop, including the flywheel and pressure plate. Another deuce owner also found a loose balancer bolt after racing, so we are both using loctite this time around.

I spent about 4 hours over the holidays cleaning up the crank snout, there was some slight galling from the old balancer. I finished it up with some 600 grit paper, looks nice.

The replacement balancer fits snug when pressed on by hand, but obviously it's only about a 1/4" installed. I'm awaiting the installer tool, then I'll know for sure how things have worked out. I will change the oil, and break open the filter to see how it looks.