When rebuilding or servicing the engine, use a calibrated torque wrench to avoid stripping the aluminum threads of the engine casings.
Loosen the locknut, turn the adjuster screw until you feel a slight drag on the feeler gauge, and tighten the locknut while holding the adjuster steady.
The 253FMM engine is an incredibly forgiving, simple piece of machinery. By keeping the oil fresh, cleaning the internal oil screen regularly, and checking your valve clearances every few thousand miles, this 250cc twin platform can easily pass 30,000 miles of reliable service. Always keep a copy of the explicit structural wiring diagram and fluid capacities on hand in your workshop before attempting an internal engine teardown. 253fmm service manual
Starting Clutch System (Lifan 253FMM engine) (CBT250 Twin) * Compatibility Brand/Model: * SUMCO: Quad Gobi GB250-E2 (bicilindrico) motorrecambio.com
The number one killer of the 253FMM is stripped drain plugs and cracked valve covers. The service manual lists torque in Newton-meters (Nm). Buy a cheap 1/4-inch torque wrench. It will pay for itself the first time you avoid stripping the oil drain bolt (spec is usually only ). When rebuilding or servicing the engine, use a
Ensure you are not using automotive engine oils containing friction modifiers (labeled "Energy Conserving"). Adjust clutch cable play to maintain 10–15mm of lever free-play.
If your engine suffers from low compression (below 120 PSI), burns excessive oil, or emits blue smoke, a top-end rebuild is required. Disassembly Remove the engine from the motorcycle frame. By keeping the oil fresh, cleaning the internal
API SG or higher, JASO MA or MA2 certified. Use 10W-40 for temperate climates, or 20W-50 for consistently hot ambient environments. Never use automotive oils with "Energy Conserving" labels, as they contain friction modifiers that will cause the motorcycle's wet clutch to slip. Cleaning the Internal Filters
0.05 mm to 0.07 mm (0.002 to 0.003 inches)
The 253FMM uses a twin-carburetor setup. Servicing these requires the manual to identify the correct jets and settings for your altitude and climate. The manual will guide you through the disassembly, cleaning, and adjustment of the carburetors, including the idle mixture screws.