Chainsaw Repair

Perhaps, although the blowdown is likely the real issue. I put the New crank and bearings in the case and buttoned it up tonight so I'll be able to see what the original and altered timing number are.

I find it interesting that dolmar went to the slab piston in the 7900. Not that I don't think it works well but, however, the original piston was designed with asymmetric windows in the piston which were done for a reason and took a lot of thought and engineering. I'm very curious why they dropped that piston for the slab side?? Can the slab side be lighter? Hard to believe, but perhaps they opted for a lighter piston when the crank issues came up?

On a side note, the New crank I pressed into the bearings/crank halves had a lot more interference fit than any previous 7900 I've worked on. Almost Stihl tight!!! Lol