Sidewinder wrote:When I run my U the first year it was running smooth only on low rpm. I seamed to pull happily up hills in high gear and low rpm. In highway-speeds it was not smooth. The vibrations where so bad that my boots kept sliding of the footboards. The two front tubes actually cracket above the sidecar loops under previous ownership. And I kept loosing nuts and bolts. The balance factor was lower than 50% with aftermarket pistons (cant remember the exact figure anymore).
During rebuild the flywheels where rebalanced to 55%. No change in cylinder/top end/cams during rebuild. The motor now runs smooth at any rpm you dare to take her to. Maybe a litle bit less smooth at very low rpm than the previous setup. And I have not retightened a singel nut in 10 seasons now (and no nylock or tread locker anywhere).
This is my experience, not a scientific evaluation. Might be some factor I have not taken in concideration. But I think it is safe to say that the higher balance factor had no bad effects on my motor.
My contention is that the bad vibrations that were shaking your chassis apart were "mechanical" and not a balancing issue, such as the flywheels loosing their trueness. The vibrations came out in the wash of the rebuild, and I suspect that it would have even without the re-balancing.
Even if the aftermarket pistons were forged, the added weight lowers the factor perhaps a couple of percentage points at most.