This Naraku 70cc Big Bore Cylinder Kit (SKU 137-26) takes an air-cooled horizontal Minarelli 2-stroke, the engine used in the Yamaha Jog and Zuma and in many other 50cc scooters, up to 70cc with the stock crankshaft. It is a complete bore-up kit with a 47mm cylinder, a low-friction molybdenum-coated flat-top piston, rings, a 10mm wrist pin, circlips, and head, base, and exhaust gaskets.
Features
-
70cc displacement: 47mm bore raises a 50cc engine to 70cc with the stock crank.
-
Moly-coated piston: Low-friction flat-top piston reduces wear.
-
Complete kit: Includes cylinder, piston, rings, wrist pin, circlips, and a full gasket set.
-
Exhaust flexibility: Works with a stock or performance exhaust.
-
Head options: Runs with the stock head for higher compression or with a larger 70cc head.
Kit Contents
- Cylinder, 47mm bore
- Molybdenum-coated flat-top piston with Naraku logo
- Piston rings
- 10mm wrist pin (wrist pin bearing not included)
- Circlips (x2)
- Head gasket
- Base gasket
- Exhaust gasket
Specifications
-
Part number: 137-26
-
Displacement: 70cc with stock crankshaft
-
Cylinder bore: 47mm
-
Cylinder sleeve outer diameter: 50.5mm
-
Wrist pin diameter: 10mm
-
Wrist pin bearing: Not included
-
Cooling: Air-cooled only
-
Engine type: Air-cooled horizontal Minarelli 2-stroke
-
Brand: Naraku (aftermarket)
Model Fitment
This kit fits air-cooled horizontal Minarelli 2-stroke engines that use a 10mm wrist pin.
| Make |
Fits |
Does Not Fit |
| Yamaha Zuma |
Zuma 50 (2002-2011), horizontal AC Minarelli, engine code 5YW / CW50 |
Zuma 1989-2001 (vertical Minarelli) or Zuma 50F / 50FX 2012+ (4-stroke) |
| Yamaha Jog and Vino |
Jog 50 (1992-2001), Vino 50 2-stroke |
Aerox and other liquid-cooled models |
| Genuine |
Buddy 50, RoughHouse 50 (horizontal Minarelli-type engine, 10mm wrist pin) |
|
| Aprilia |
Scarabeo 50 (1993-2006), SR50 air-cooled (1994-2002) |
SR50 LC (liquid-cooled) |
| CPI |
Oliver 50, Hussar 50, Popcorn 50 |
|
| E-Ton |
Beamer 2 |
|
| Malaguti |
Ciak 50 (2002-2005), F10, F12 AC, F15 AC, Yesterday 50 (2001-2006) |
Liquid-cooled versions |
| Benelli |
Pepe 50, Andretti 50 |
|
| Adly |
Thunder Bike 50 |
|
| MuZ / MZ-Moskito |
RX50, SX50 |
|
| Chinese 2-stroke clones |
1E40QMB / 1PE40QMB engines with a 10mm wrist pin |
Clone engines with a 12mm wrist pin |
Check the engine on your scooter before ordering. Confirm it is air-cooled and horizontally mounted, and measure the wrist pin. Some 1E40QMB / 1PE40QMB Chinese clone engines use a 12mm wrist pin instead of 10mm, and this kit will not fit those.
Installation Notes
-
Cylinder sleeve clearance: The sleeve outer diameter is 50.5mm. Some engine cases need light filing or machining at the case mouth so the skirt slides in smoothly.
-
Carburetor and jetting: Going from 50cc to 70cc requires upjetting the main jet, typically 10% to 15% larger, to avoid running lean and seizing the piston.
This product is intended for off-road use only. This product is not intended for use on public roads or land.
