Naraku QMB139 52.4mm Performance Cylinder & Head Kit
Naraku QMB139 52.4mm Performance Cylinder & Head Kit
$314.64
10 in stock
*Note: Free shipping to U.S. mainland (excludes AK, HI, and territories)
Orders placed by 1pm EST on weekdays ship the same day.
Product Details
Description
Naraku 139GMB 52.4mm Big Bore Cylinder & Head Kit | 89.3cc
Key Details
- NK100.52
Specifications
- Height: 36.3mm Compression Height (from center of wrist pin hole to top edge of piston): 20mm Non-emissions style head Intake valve: 23mm Exhaust valve: 20mm Intake Port Diameter: 20.8mm Exhaust Port Diameter: 18.7mm Uses Short 64mm Valve Stems QMB139 50cc/49cc , Various unlisted makes/models NOTE: replaces Cylinder Heads with 64mm Valves (Short Valve Style). Please see Related Items if you need 64mm valves. You may need to modify your engine case to accommodate the larger cylinder. Upgrades to 89.3cc Cylinder Bore: 52.4mm Cylinder Sleeve Outer Diameter: 54.4mm Wrist Pin Diameter: 13mm Total Piston Height: 36.3mm Compression Height (from center of wrist pin hole to top edge of piston): 20mm Non-emissions style head Intake valve: 23mm Exhaust valve: 20mm Intake Port Diameter: 20.8mm Exhaust Port Diameter: 18.7mm Uses Short 64mm Valve Stems QMB139 50cc/49cc , Various unlisted makes/models
Compatibility / Fitment
Use the fitment details below to confirm this part matches your scooter before ordering.
- Engine Size: 49cc, 50cc, QMB139
- Engine Code: QMB139
- Fitment Notes: Big Bore, Performance
Fitment Guide: This compatibility information is based on manufacturer and supplier data. Listed models are common known applications and may not include every compatible scooter. If your scooter has multiple versions or production changes, confirm the correct match before ordering. Check photos, measurements, original part numbers, engine code, model, and related fitment information whenever possible.
Common Fitment Questions
Q: Will this fit a QMB139 engine?
A: This SKU is listed as compatible with QMB139 engine-code fitment. Always compare your original part and scooter details before ordering.
Q: Is this for 49cc scooters?
A: This SKU is listed with 49cc engine-size fitment. Confirm exact model, year, and part style before ordering.
Additional information
| Weight | 4.7 lbs |
|---|---|
| Dimensions | 7 × 7 × 9 in |
Unlock serious performance gains with the Naraku QMB139 52.4mm Big Bore Cylinder & Head Kit. Engineered for QMB139 4-stroke 50cc engines, this complete kit bumps displacement to 89.3cc with a stock 41.4mm stroke — or all the way to 94.9cc when paired with a 44mm stroker crank. Everything you need for the swap is included.
What's Included
- Cylinder (52.4mm bore)
- Piston, rings, piston pin & circlips
- Cylinder head
- Head gasket & base gasket
Key Features
- Big Bore Upgrade — increases displacement from 50cc to 89.3cc (stock stroke) or 94.9cc (44mm stroker crank)
- Racing-Grade Head — non-emissions style head with larger 23mm intake and 20mm exhaust valves for improved flow
- Short Valve Stem Design — replaces cylinder heads with 64mm short-style valve stems
- Precision Porting — 20.8mm intake port and 18.7mm exhaust port for optimized airflow
- Cylinder Bore: 52.4mm
- Cylinder Sleeve OD: 54.4mm
- Wrist Pin Diameter: 13mm
- Total Piston Height: 36.3mm
- Compression Height: 20mm
- Intake Valve: 23mm
- Exhaust Valve: 20mm
- Intake Port: 20.8mm
- Exhaust Port: 18.7mm
- Valve Stem Length: 64mm (short style)
- Displacement (stock stroke): 89.3cc
- Displacement (44mm stroker): 94.9cc
- Compatible Engine: QMB139 49cc/50cc 4-stroke
- SKU: 137-4
Fitment Notes
- Compatible with 139QMB 50cc/49cc engines
- You may need to modify your engine case to accommodate the larger cylinder
- Replaces cylinder heads with 64mm short-style valve stems only
This product is intended for off-road use only and is not intended for use on public roads.
