Hoca 169-149 16X13 6 Gram Roller Weights for 50cc and Larger Scooters Hoca - SSP-G Roller Weights size 16x13 for 50cc 4-stroke QMB139 engines. The QMB139 is the most popular 50cc 4-stroke engine found on Chinese scooters.We recommend starting performance upgrades by changing the variator roller weights first.Heavier roller weights= A slower take off speed with more acceleration and a higher top speed. Lighter roller weights = A faster take off speed with less acceleration and lower top speed. Please see our Warranty & Returns Policy.