Suzuki Madura GV700GL Service Manual page 199

EMISSION CONTROL
&
REGULATIONS 7-4
HYDROCARBONS
Hydrocarbons are unburnt gasoline vapors and can be measured in two different ways. The first is to
measure the weight of the pollutants over a specific distance such as grams per mile or grams per kilometer.
The second method is to measure the concentration of HC in the exhaust gas in parts per million (PPM).
The most common cause of high HC emissions are ignition system problems. If the ignition system fails to
ignite the fuel mixture properly, then raw gasoline vapors will pass through the engine into the exhaust
system. Listed are the most common ignition problems which occur and which can affect HC emission
output.
IGNITION SYSTEM MALFUNCTIONS
1. Spark Plugs- Fouled, dirty, improper type or improperly gapped.
2. Ignition Timing- Advanced or Retarded.
3. Timing Advance- Too fast or too slow an advance rate.
4. Battery - Low charge or faulty.
Carburetion can also lead to high HC emissions if the mixture is either excessively rich or excessively lean.
MIXTURE-RELATED MALFUNCTIONS
1. Air Cleaner- Dirty, over oiled or torn.
2. Jets - Clogged, restricted or incorrect size.
3. Float Level - Level too low (lean) or too high (rich).
4. Choke- Leaking choke plunger or sticking linkage.
5. Air Leaks- Intake manifolds, engine gaskets and other sealing surfaces.
6. Synchronization- Unbalanced on multi-cylinder machines.
7. Exhaust System- Restricted flow or improper exhaust system.
Engine wear or damage can also cause high HC emissions.
1. Rings- Low compression, leakage into crankcase.
2. Valves- Improper adjustment, bent stem or burnt.
3. Gaskets- Leaking, loss of compression.
4. Crank Seals- Leaking.
5. Oil Consumption- Worn valve guides, worn rings, clogged crankcase breather.
6. Oil- Improper engine oil.