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This procedure can be easily adapted to any gasoline engine, but here's the short version for an MV with three-groove pulley :
Step 1: Pretend you never ever read or heard of the official timing procedure. You will not connect or disconnect anything except your strobe light.
Step 2: Make a mark on forward pulley rim 2" clockwise from the dished TDC mark. This mark indicates 35º BTDC for cyl. #1 or #3.
Step 3: On warmed up engine connect basic (non-advancing) strobe to read cyl. #1 plug wire.
Step 4: Rev engine to 3000rpm or higher, the 35º mark you made should be aligned with the case center seam. Adjust distributor position until it is.
Step 5: Test drive, add as much as 5º to 10º additional advance if performance improves while monitoring for pinging at less than 3000rpm, under full load and hot.