(3) CHECKING THE CARBURETOR
n
Remove the carburetor from engine.
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Remove the float chamber from the carburetor and check to see if the main jet or the pilot jet has been
clogged up. (Refer to Section 10-5-2 on page 59.)
Use a compressor and high-pressure air to blow the clogged dust or gum out of the jets and fuel passage.
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Remove the float pin and the float.
Check the needle valve.
If the needle valve is worn, replace it and the valve seat.
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Clean and re-assemble the carburetor.
11-1-3 CHECK THE COMPRESSION
If the engine’s starting difficulty or power drop has not been caused by a faulty ignition or fuel system, the
final step is to check the compression of the engine.
1) Check the spark plug.
Loose or broken spark plug can cause low compression. If the spark plug is broken, replace with a new
one.
2) Check the head gasket.
Remove fuel tank, head cover and cylinder head to check the head cover.
If the head gasket is broken, replace it with a new one.
3) Remove carbon deposits from the cylinder head and piston top.
4) Check and adjust the tappet clearance.
5)
Check the valve system.
Remove any carbon deposits from the valves, valve seats, intake and exhaust ports and valve guides.
If the valve face or the valve guide is worn, replace it.
Check and adjust the tappet clearance when reassembling. (Refer to Sections lo-4-2-(8) and lo-4-2-(9)
on pages 51 and 52.)
6) Check the piston and piston rings.
If the compression is still not sufficient, you’ll have to dismantle the engine and examine the piston and
piston rings.
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Disassemble the engine and remove the piston and piston rings.
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Check the piston rings and grooves.
Clean off any carbon or gum deposits from the piston rings and grooves.
If a piston ring is worn, replace with a new one. (Refer to Section lo-4-2-(3) on page 48.)
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