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The chain and sprocket rub against each other. Check whether the left and right adjusting scale position of rear wheel is consistent.
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It ‘s a normal phenomenon, because the metal will expand when it’s heated .
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The chain and sprocket rub against each other.
Check whether the left and right adjusting scale position of rear wheel is consistent.
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Reasons:
(1) The mixture is too thick or too thin.
(2) Ignition time is too early or too late.
(3) Low fuel rate, engine leakage.
(4) Blockage of air filter.
Solutions:
(1) Replacement of fuel with higher octane number.
(2) Clean the exhaust and air filter.
(3) Keep the fuel supply system unobstructed.
(4) Adjust the mixing ratio screw of carburetor to get the best mixing ratio.
(5) Check the installation position of the magneto. Adjust ignition time as required.
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(1) Check whether the throttle switch is returned or not.
(2) Check whether the carburetor throttle valve is reversed.
If the throttle valve is reversed, the throttle turning stroke will be very big.
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(1) Check if there are spark at the high pressure cap.
(2) Check whether the carburetor has oil, and unscrew the oil drain nut of the carburetor with screwdriver.
(3) Check the connection between carburetor and intake pipe for tearing off dust-proof gummed tape.
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(1) When impurity gasoline is used, there are impurities left in the combustor that can not be fully burned. The piston, piston ring and cylinder are worn out.
(2) Improper use. Running the engine at high speed or overloading before running-in period, which causes the abrasion of piston and piston ring.
(3) Failure to maintain , improper maintenance and adding inferior oil, resulting in wear and tear of piston, piston ring and cylinder.
(4) When the piston is abrading, there is a gap between the piston and the cylinder block . The air pressure in the cylinder block surges back to the crankcase and flow out of the exhaust pipe.
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Reasons:
(1) Fuel is used up or not available.
(2) Short circuit or open circuit of ignition coil.
(3) Short-circuit or open-circuit of inner coil of magneto.
(4) The spark plug was broken down.
(5) Wire plug off.
(6) Crankcase leaks seriously.
(7) Overheating of engine results in holding tile cylinder.
Solutions:
(1) Adding fuel.
(2) Repairing or replacing ignition coil.
(3) Repairing or replacing the magneto.
(4) Replacing spark plugs.
(5) Re-insert the wire plug.
(6) Repairing the air leakage part of crankcase.
(6) Replacing engine bushes and cylinder.
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Reasons:
(1) Engine works at high power and overload for a long time.
(2) The fuel mixing ratio does not meet the requirements.
(3) Clutch skidding.
(4) Poor heat dissipation.
(5) Ignition time is too late.
Solutions:
(1) Use it in the right way.
(2) Use fuel according to regulation and mix it well.
(3) Adjust the clutch’s stroke and replace the friction plate if necessary.
(4) Clean up the carbon deposit and greasy dirt in the exhaust.
(5) Check the installation position of the magneto and adjust the ignition angle.
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(1) Check whether the upper and lower steel balls are reversed. Some models can be interchanged (e.g. CG, KC etc.) and some models can not be interchanged (e.g. SL200-8/SL150-4, SL125-30 etc.)
(2) Check whether the steel balls are reversed or not. The steel balls must be flexible with the axle-bowl track.
(3) Check whether the upper shaft bowl is missing.
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Clutch’s left brake handle stroke is too large, the correct free stroke should be within 10-20. That the stroke is too big makes the clutch separate incompletely , leading to gear shifting can not be switched. If the stroke is too small, clutch are always in a semi-clutch state, accelerating abrasion of the clutch .
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Reasons:
(1)Abnormal noise of cylinder, piston and piston ring parts.
(2)Abnormal noise of connecting rod, crankshaft and flywheel.
(3)Abnormal noise from fuel chamber.
Solutions:
(1)Choosing the suitable gasoline.
(2)Adjusting ignition time.
(3)Replacing worn parts.
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The throttle switch can not be completely relaxed, otherwise it will be stalled.
Reasons:
(1) Carburetor idle shut off valve adjusting screw and idle air adjusting screw are not properly adjusted.
(2) Idling measuring hole blockage.
(3) Leakage of carburetor joint crankcase and intake valve plate.
(4) Carburetor float chamber oil level is too low.
Solutions:
(1) Re-adjust carburetor shut off valve adjusting screw and idling air adjusting screw.
(2) Clean up the idle measuring hole.
(3) Check and repair the leakage parts of carburetor joint, crankcase and intake valve plate.
(4) Re-adjust the oil level in the carburetor float chamber.
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The engine shakes, when the engine idles . At the same time the speed of the engine varies from high to low, and the engine is unstable.
Reasons:
(1) Blockage of air filter
(2) Spark plug clearance is too small.
(3) The combustible mixture is too thick or too thin.
(4) Ignition time is too early.
Solutions:
(1) Clean the filter element of the air filter.
(2) Adjust spark plug clearance.
(3) Adjust the carburetor.
(4) Re-install the magneto.
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Reasons:
(1) The free stroke of clutch-operated cables is too small or even no have.
(2) Improper adjustment of clutch adjusting screw.
(3) Insufficient or uneven pulling force of clutch spring.
(4) Clutch wear.
(5) Clutch steering wire is jammed.
(6) Clutch active disc grinding groove, blocking the axial movement of active plate..
Solutions:
(1) Adjusting Free stroke.
(2) Clean friction discs and replace them when it is severe wear and tear.
(3) Clutch springs should be replaced in groups when the elasticity is insufficient.
(4) When the control mechanism is stuck,lubricating will be necessary, and checking the reason completely.
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Phenomenons:
(1) When a motorcycle is running, the clutch handle can't effectively reduce the speed of the motorcycle though it is grasped tightly.
(2) It is difficult to shift gears. When shifting gears, there is gear impact sound in the gearbox.
(3) When the engine automatically stalls with the stop of the motorcycle , although tightening up the clutch handle can not effectively reduce the speed of the motorcycle.
Reasons:
(1) The improper adjustment of the clutch and the excessive free stroke make the actual stroke on the clutch less than the distance required for the complete separation of the clutch.
(2) Uneven elastic force of clutch compression spring.
(3) Clutch lubricating oil is too viscous or has been used for too long, resulting in incomplete separation of main and follower plates; clutch has impurities.
Solutions:
(1) Adjustment of free stroke.
(2) Clean the friction discs and replace them when they are severely worn out.
(3) When the spring of clutch is insufficient in elasticity, it should be replaced in groups. When the control mechanism is stuck, it should be lubricated, maintained or overhauled.
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Reasons:
In a certain gear, the gear retreats naturally without manipulation.
(1) Improper operation,like shifting improper.
(2) The claws are worn and the edges are rounded.
(3) Wear of shift cam and fork.
(4) Inappropriate assembly, resulting in inadequate gear engagement.
Solutions:
(1) Correct operation.
(2) Replacement of claws.
(3) Replacement of shifting cams and forks.
(4) Reassemble and readjust it.
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Shift to the first gear, but have abnormal noise in engine and the motorcycle can not move, the motorcycle can only start in second gear.
Reason: Assembling the first-gear driven gear reversely.
Solution：Re-install the first-gear driven gear.
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Starter rod is easy to push down and engine does not start.
Reasons:
(1) The edge of the starter block is ground into rounded corner.
(2) The top pin of the starter block can't bounce up.
(3) The first-order driving gear falls off
Solutions:
(1) Replacement of pawl block
(2) Replacing the top pin spring of the pawl block
(3) Re-install the driving gear.
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After the boot rod is trampled down, it can not bounce back.
Reasons:
(1) Inadequate elasticity or breakage of start-up return spring.
(2) Over-tightening of the starting shaft with the side cover hole of the clutch.
(3) Start-up shaft deformation.
Solutions:
(1) Replacement of start-up return spring.
(2) Adjusting the matching position between the starting shaft and the side cover hole of the clutch.
(3) Replacement of starting axle.
