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What are the possible causes making a motorcycle exhaust exceeding the standard?

CO

 

HC

 

POSSIBLE CAUSE

 

HIgh

 

Normal

 

The gas-oil ratio is too high.

 

Normal

 

High

 

1. The ignition system is not in good condition
Ignition timing is not correct
Spark plug is clogged or its gap is not proper
The platinum contact or the capacitor is not good.
The ignition coil is not good
Distributor cap or distributor is not good or electrically leaking
2. Valve timing is not properly adjusted
3. Exhaust valve is scratched

 

Low

 

High

 

1. Gasoline-air mixture is too thin, causing improper ignition
2. Vacuum leakage
vacuum connector
Intake manifold
joint washer

 

High

 

High

 

1. The air filter is blocked
2.Carburetor is not good; idle mixture is rich; float is installed incorrectly; air choke is not functioning; strong valve is loosen; idle mixture screw or needle seat is scratched.
3.PCV valve is loosen