The Zenoah G2D-58 is the original 2 stroke power plant of the California Goped. The Zenoah G2D-58 is the predecessor to the Zenoah G23LH slant plug engine. What's special about this model is a straight plug engine design and higher top end power than the successor, its feel is like the rc engines we have today but a little more finicky. It was the power-plant for many Goped scooters, including the Goped Sport, Goped Liquimatic, Goped Go Quad
- Displacement: 22.5cc
- Piston Rings: 2, also 1 ring version
- Compression: 8.4:1
- Transfer Ports: 2
- Reed: No
- Carburetor: G2D-1140--Walbro WY-1A;G2D-1148--Walbro WA-167
- Stock Carb Settings: 1/4 turn out both jets
- Oil Mixture: 25:1
- Horsepower: 2.0
- Net Power: 1.2
- Rotation (output side): counter-clockwise (PTO side)
- Clutch Diameter: 54mm
- Ignition System: magneto with external rectifier/module
- Idle RPM: 4000 +/- 300 rpm
- Max RPM: ~12000 rpm 1140 version, ~14000 rpm HP 1148 version
- EPA Compliant: no
- C.A.R.B. Compliant: no
- Fuel Type: Supreme unleaded; 91 octane or higher
The Engine. It is still fairly easy to get one, but has steadily begun to be more and more difficult since Goped switching their main power plant in 1995 to the G23LH, and the recent transition from Japanese built Zenoah G2D Komatsu engines to more cost effective Taiwanese built Chung Yang(CY) engines of a similar, slightly higher spec.
Parts and Service. Parts are becoming a bit scarce since the transition in 1995 to the G23LH, but they are available. There is also a slightly stronger brother of this engine; the G2D-HP 1148 (G2D-70 and G2D-96-D versions), at 2.0hp this engine loves to be opened up and power seems endless.
On a completely stock Zenoah G2D-58 maintenance is minimal. After every 100 hours of use, clean the air filter, check the spark plug for signs of wear and if wear is visible replace with N.G.K BM7A or equivalent (NGK BM6A is perfect for this engine). Gap the plug at .024"-.026". Check fan cover for debris and check clearance between magneto and flywheel. Clearance should be about business card thickness, after that you should be good for another 100+ hours of riding, and check head bolts for proper torque spec; usually around 25lbs each.
With its single jet adjustable barrel carburetor, 2 piston rings, and a hefty die cut exhaust gasket, the 2D is beast of a machine, the most reliable engine? yes and no... The Zenoah G2D-58 was designed to be used on outdoor equipment not scooters, but proved a success when it was first adapted to a Goped scooter.
The engine was able to get the rider from point a to point b quick and easy, or until it is out of fuel. This engine like the G23LH can take some serious abuse, but if it is taken care of, it can almost live forever. Modification and or excessive use of this engine have a tendency to ruin the ignition module, rendering it unable to get past 3500rpm causing it to instantly hit the rev limiter.
Remember a stock engine will outlast a lightly modified engine, a lightly modified engine will outlast a moderately modified engine, and a heavily modified engine will breakdown before any of the above need to fill up the next tank of gas.