Modenas GT128: Essential Owner’s Guide 1. Key Specifications | Parameter | Specification | |-----------|----------------| | Engine Type | 124.8cc, 4-stroke, single cylinder, air-cooled | | Bore x Stroke | 54.0 x 54.4 mm | | Compression Ratio | 9.3 : 1 | | Maximum Power | ~10.9 hp @ 8,500 rpm | | Transmission | 5-speed, constant mesh | | Starter System | Electric & Kick | | Fuel Tank Capacity | 4.8 Liters (Reserve: ~1.2L) | | Engine Oil (with filter) | 0.9 Liters | | Engine Oil (without filter) | 0.8 Liters | | Spark Plug | NGK CR7HSA | | Tire Pressure (Front) | 200 kPa (29 psi) | | Tire Pressure (Rear) | 225 kPa (33 psi) | 2. Controls & Indicators (Dashboard)
Fuel Gauge: Bars decrease as fuel level drops. High Beam Indicator: Blue light. Turn Signal Indicator: Green flashing light. Neutral Indicator: Green 'N' light. Low Oil Indicator: Amber light – stops the ignition if oil is critically low (safety feature). Cooling Fan Light: Turns on when radiator fan is active (rare on GT128 – check if yours has it).
3. Starting Procedure (Cold Engine)
Turn fuel tap to ON (downward position). Turn ignition key to ON . Ensure transmission is in NEUTRAL (green light on). For electric start: Press starter button. For kick start: Fold out kick lever, push down firmly with a full stroke. Allow engine to idle for 1-2 minutes before riding. Modenas Gt128 Manual Book
Hot engine start: Open throttle slightly (1/8 turn) while pressing starter.
4. Break-in Period (First 1,000 km)
0 – 500 km: Do not exceed 4,000 RPM. Vary speed, avoid full throttle. 500 – 1,000 km: Do not exceed 6,000 RPM. Short bursts of acceleration OK. After 1,000 km: Change engine oil and oil filter. Then normal riding. Modenas GT128: Essential Owner’s Guide 1
5. Maintenance Schedule (Every distance or time, whichever first) | Item | Every 1,000 km | Every 4,000 km | Every 8,000 km | |------|----------------|----------------|----------------| | Engine Oil | Replace | Replace | Replace | | Oil Filter | - | Replace | Replace | | Spark Plug | Inspect | Replace | Replace | | Air Filter | Clean | Replace | Replace | | Valve Clearance | - | Inspect/Adjust | Inspect/Adjust | | Drive Chain | Lubricate/adjust | Clean & lube | Replace if worn | | Brake Fluid | Check level | Replace | Replace | | Coolant (if liquid-cooled variant) | Check | Replace | Replace | Valve clearance (cold engine): Intake 0.08–0.12 mm, Exhaust 0.12–0.16 mm 6. Fuel Tap Positions (Vacuum type)
ON – Normal running (arrow pointing down). RES – Reserve (arrow pointing up). Use when fuel runs out. PRI – Prime (arrow horizontal). Bypasses vacuum – use if carburetor is dry after maintenance. Do not ride in PRI – will flood engine.
7. Chain Adjustment (Chain slack: 20–30 mm) High Beam Indicator: Blue light
Loosen rear axle nut. Turn left and right adjusters equally. Tighten axle nut to 65 Nm . Check wheel alignment using chain adjuster marks.
8. Common Troubleshooting | Symptom | Likely Cause | Action | |---------|--------------|--------| | Engine won't start | Fuel tap OFF or in PRI | Turn to ON/RES | | | Low oil (indicator on) | Add oil (must turn off/on ignition to reset) | | | Clutch lever not fully pulled (if in gear) | Pull clutch or shift to N | | Engine dies when idling | Idle speed too low | Adjust idle screw (~1,300 ±100 rpm) | | Weak brakes | Air in brake line | Bleed brakes | | | Worn pads | Replace pads | | Headlight dim | Engine not running (AC headlight) | Start engine | | Overheating | Low coolant (if applicable) | Top up coolant | | | Slow speed heavy traffic | Stop and cool down | 9. Lubrication Points (every 3 months)