Originally Posted by Bombardier
part of the reason the larger engine rattles more is because the larger the capacity the greater the heat build up so the more piston to bore clearance needed. basicly the 66 cc engine usually has more clearance betweent he piston and bore than say a 50 cc engine . also you have a larger piston rattling around inside there .my 66 is the same .
the 50 made a grinding noise only when you pulled in the clutch because the retaining screw on the flower nut was touching the side cover only when i pulled the clutch in .i put 2 gaskets ont he side cover and the grinding noise went away
My bigger 67cc engines have less engine noise, the 62 does have more clutch noise and more general engine noise, the oher smaller engines that i see around town seem to be more noisy as well.