GENERAL INFORMATION
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4. Check for retarded ignition timing. A decrease in power results when the plugs fire later than normal
5. Check for one or more of the following problems
a. Low engine compression
b. Worn spark plug
c. Fouled spark plug
d. Incorrect spark plug heat range
e. Weak ignition coil
f. Incorrect ignition timing
g. Plugged throttle passages
h. Incorrect oil level (too high or too low)
i. Contaminated oil
j. Worn or damaged valve train assembly
k. Engine overheating
6. If the engine knocks when it is accelerated or when running at high speed. Check for one or more of
the following possible malfunctions:
a. Incorrect type of fuel
b. Lean fuel mixture
c. Advanced ignition timing
NOTE
Other signs of advanced ignition timing are engine
overheating and hard or uneven engine starting
d. Excessive carbon buildup in combustion chamber
e. Worn pistons and/or cylinder bores
Poor Idle or Low Speed Performance
1. Check for an incorrect pilot screw adjustment
2. Check for damaged or loose intake pipe and air filter housing hose clamps. These
conditions will cause an air leak
3. Perform the spark test in this chapter. Note the following:
a. If the spark is good. Go to Step 4
b. If the spark is weak. Perform the Peak Voltage Testing
4. Check the ignition timing. If ignition timing is correct. Perform Step 5. If the timing is
incorrect. Perform the Peak Voltage Testing
5. Check the fuel system as described in this chapter
Poor High Speed Performance
1. Check ignition timing. If the ignition timing is correct. Perform Step 2. If the timing is incorrect.
Perform the Peak Voltage
2. Check the fuel system as described in this chapter
3. Check the valve clearance as described. Note the following:
a. If the valve clearance as correct. Perform Step 4
b. If the clearance is incorrect. adjust the valves clearance as described in Chapter Three
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