Main Menu
Your Cart

Polini Cylinder 50mm 81cc Nikasil Bore Kit w/Cast Piston Plus Weights (139QMB)

Polini Cylinder 50mm 81cc Nikasil Bore Kit w/Cast Piston Plus Weights (139QMB)

Description: Polini Cylinder 50mm 81cc Nikasil Bore Kit with Cast Piston Plus includes CVT roller weights for 139QMB 49/50cc 4-stroke engines. This increase in bigger bore displacement leads to an increase in performance and acceleration. The use of aluminum for this cylinder with coated chrome/nikasil plating offers superior durability and ensures very good cooling properties.

It’s also recommended to get a 50mm big valve head (Part# 1100-1239) in order to take full advantage of the bigger piston valve notch. However, you can use the original stock cylinder head without any problem.

When used in conjunction with a stock stroke of 41.4mm the engine displacement comes out to 81.3cc! When used with a 44mm stroker crank, engine displacement = 86.4cc!

NOTE: Please, measure with a caliper 139QMB crankcase bore (opening) for 54.5mm cylinder outer diameter sleeve need a minimum 54.6mm bore clearance or boring and machining are required. If, engine case must be bored, order an engine bore tool (Part# 1400-1001). 


Includes the following Cylinder, Piston + Rings, Gaskets (compression base gaskets, steel head gasket), Wrist pin, Circlips, Roller weights, and Variator slides.

•    1x Cast-Alumin Piston: 50mm
•    5x Piston Rings: 50mm
•    1x Wrist Pin w/C-clips: 38x13x9mm 
•    1x Cast-Iron Nikasil Cylinder: 50mm
•    Outer Sleeve Diameter 54.5mm
•    Cylinder Height (w/o sleeve): 53mm
•    Overall Height (w/sleeve): 70.3mm
•    6x Roller Weights: 16x13mm 5gm<9gm
•    3x Plastic Variator Slides
•    Made in Italy
•    Fit Intake Studs: M6 / Nuts: M6 Socket: 8mm
•    Fit Exhaust Studs: M6 / Nuts: M6 Socket: 8mm
•    Fit Rocker Arm Assembly: 64mm or 69mm / Feeler Gauge: .004in / .005in / Socket: 9mm
•    Fit Cylinder Studs: 168mm 176mm / Nuts: M7 / Washers: M7 / Socket: 10mm
•    Fit 50mm Stud Spacing /Diagonal 70.5mm
•    Fit Cylinder Head 50mm 2V
•    Fit Crankshaft 41.4mm to 44mm
•    Fit Dowel Pin Set (
•    Fit QMB 49/50cc+

Supported Models: GY6 139QMB 49cc-50cc 4-Stroke engines, Filly 50, Kymco 50, QLink 50, SYM 50, TaoTao 50

Item Weight & Package Dimensions:
•    2.869 pounds | 5.7
” (L) x 5.7” (W) x 4.669” (H)

Write a review

Note: HTML is not translated!
Bad Good
Polini Cylinder 50mm 81cc Nikasil Bore Kit w/Cast Piston Plus Weights (139QMB)
  • Stock: 40
  • Reward Points: 11
  • Part #: 125.0007
Sold: 0
Views: 821
Price in reward points: 296