Backtracking on the BSA project a bit, the biggest obstacle to repairing the engine was the enormous crack that had developed in the crankcase.
No one I spoke to had ever seen a crack in that position before, and our best guess was that, over the years of sitting without a piston or cylinder head, the case had filled with water, froze, and split at the seam. Regardless, The case could certainly not be used like that, especially since 2-strokes rely on a pressure-tight bottom end to function correctly. I brought the case to a local welder to have the crack patched up, but the results were not...encouraging.
Either there was still oil contamination in the crack, or the welder wasn't familiar with the material, but the results were extremely sloppy and porous. I ground down the inner weld only to find numerous blow-holes and voids. It was only a lack of available donor cases that kept me from scrapping this part entirely. I spent a week hand grinding and filing the weak welds down:
...and then was able to find a different welder who specialized in cast aluminum repair. His results were a huge improvement, and wiped away most of the irregularities left by the previous guy. I fixtured the case into my ancient milling machine to clearance the inside of the case for the crankshaft:
and decided to leave the outer weld bead alone. The case is so thin at this point that I decided the extra strength and material was more important.
No comments:
Post a Comment