Troubleshooting; Engine Doesn't Start Or Is Difficult To Start; Engine Lacks Power - APRILIA SR 50 Service And Repair Manual

SR 50
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1.1 Fuel doesn't reach carburettor.
– No fuel in the tank.
– Fuel pipe or carburettor filter clogged.
– Needle valve either clogged or blocked.
– Clogged tank bleed plug.
– Vacuum tap malfunctions.
– Damaged vacuum pipe.
1.2 Wet spark plug.
– Clogged carburettor float chamber bleed.
– Idling rpm too high (idling mixture too rich).
– Clogged air filter element.
1.3 Ignition spark doesn't flash or is weak.
– Defective spark plug.
– Defective spark plug cable.
– Ignition defective or in short circuit.
– Connecting contacts or terminals loose or
defective.
1.4 Engine compression loss.
– Piston segments worn or stuck.
– Damaged head gasket.
1.5 Engine starts, but stops immediately.
– Incorrect ignition phase.
– Broken intake manifold.
– Defective carburettor.
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2.1 Wheel doesn't rotate freely.
– Friction between wheel and brake.
– Wheel bearing worn or damaged.
2.2 Tyre pressure too low.
– Punctured tyre.
– Defective tyre valve.
2.3 Insufficient speed increase.
– Clogged air filter.
– Limited carburettor flow.
– Clogged silencer.
2.4 Clogged carburettor.
– Service interval too long.
2.5 Dirty spark plug.
– Insufficient spark plug service interval.
– Spark plug heat rating incorrect.
2.6 Engine overheating.
– Heavy deposits in the combustion chamber.
– Fuel quality.
– Too weak fuel-air mixture.
2.7 The engine is noisy (rattles).
– Worn piston rings.
– Too weak fuel-air mixture.
– Heavy deposits in the combustion chamber.
– Excessively advanced ignition stroke.
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– Check the fuel level in the tank.
– Clean or change the pipe and the filter.
– Clean or release.
– Clean the bleed plug.
– Change.
– Change.
– Clean the bleed.
– Adjust the idling rpm.
– Clean the filter.
– Change.
– Check and, if necessary, change.
– Check and repair.
– Check, tighten and, if necessary, change.
– Change.
– Change.
– Repeat the ignition stroke.
– Check and, if necessary, change.
– Check and, if necessary, change.
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– Check the braking system and the alignment of
the wheel.
– Change.
– Repair and, if necessary, change.
– Repair and, if necessary, change.
– Clean.
– Clean the carburettor.
– Clean.
– Service more frequently.
– Clean more frequently.
Check the gap between the electrodes.
– Replace with a spark plug with proper heat rating.
– Clean the combustion chamber.
– Use the recommended type of fuel only.
– Adjust the carburation.
– Change.
– Use the recommended fuel.
– Clean the combustion chamber.
– Adjust.
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