Bolens 643C Service Manual

Engine fails to start

1.  Spark plug wire disconnected.
2.  Fuel tank empty or stale fuel.
3.  Throttle control lever not in correct 

starting position (if equipped)

4.  Choke not in ON position.
5.  Blocked fuel line.
6.  Faulty spark plug.
7.  Engine flooding.

1.  Connect wire to spark plug.
2.  Fill tank with clean, fresh gasoline.
3.  Move throttle lever to start position. 

4.  Move lever to ON position.
5.  Clean fuel line.
6.  Clean, adjust gap, or replace.
7.  Refer to the engine manual packed 

with your unit. 

Engine runs erratic

1.  Connect and tighten spark  

plug wire.

2.  Move choke lever to OFF.
3.  Clean fuel line; fill tank with clean,  

fresh gasoline.

4.  Clear vent.
5.  Drain fuel tank and carburetor. 

Refill with fresh fuel.

6.  Refer to the engine manual packed 

with your unit.

7.  Refer to the engine manual packed 

with your unit. 

1.  Spark plug wire loose. 

2.  Unit running on CHOKE.
3.  Blocked fuel line or stale fuel. 

4.  Gas cap vent plugged.
5.  Water or dirt in fuel system. 

6.  Dirty air cleaner. 

7.  Carburetor out of adjustment.

Engine overheats

1.  Fill crankcase with proper oil.
2.  Refer to the engine manual packed 

with your unit.

3.  Remove blower housing and clean.
4.  Refer to the engine manual packed 

with your unit. 

1.  Engine oil level low.
2.  Dirty air filter. 

3.  Air flow restricted.
4.  Carburetor not adjusted properly.

Tines do no engage

1.  Stop tiller completely, check and 

discard foreign object.

2.  Replace tine clevis pin(s).
3.  Replace belt.
4.  Take unit to authorized service 

1.  Foreign object lodged in tines.
2.  Tine clevis pin(s) missing.
3.  Belt worn and/or stretched.
4.  Pulley and idler not in correct adjust-

ment.