MC crankshaft alignment and balance tool.

[petertha]

I'm intrigued by your jig. In a former life I used to race RC models 'pylon racing' (200 mph, 0.40CI 2S methanol engines, 30K rpm). So shaft TIR is a similar big deal, especially after an unfortunate 'deep dirt injection' & you are now wondering if the shaft is still good. It is indeed a tricky object to measure accurately, worse on our engines because there is no stub shaft on the other end, just the counterweight/crankpin & annular gas passage hole. So even less to reference off of like end centers.

But doesn't your entire principle rely on the main shaft being 100% true? For example if orange line is 100% concentric axis & red line is 0.001" (bent) deviation, isn't it just translating that deviation to your dial indicator as it rotates through the fixed bearings?