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I’ve overbored my Force 90 and 150 — it’s simple enough, but I stopped at 30 mil over. It makes a heckuva difference on torque and mid-range acceleration. Not sure if there are pistons available for higher than 40
From what I can see, Force 3-4-5 powerheads have a bad habit of eating the rings on the inner cylinders. This is due to oil shortage which is caused by fuel shortage (which is caused by the middle carb(s) starving.
Which leads to the conjecture of there being many failed force powerheads out there that require overboring (instead of yours which may also require rods and crankshaft repair) — maybe you can find one and bring it back to life.