Small Engines (Lawn Mowers, etc.): Stihl HS45, air leaks, compression load

Question
Trimmers are four years old, but get minimal residential use.  Ran for five minutes after first start of the season but while using it instantly quit running. Now it won't start...doesn't act like plug is firing.  Carb is clean, plug is not cracked, fuel lines appears fine.  Any advice?

Answer
HI CHRIS

SOUNDS LIKE A HEDGE TRIMMER  MODEL BEING HS45

HAVE YOU CHECKED THAT MUFFLER IS NOT BLOCKED ?
ARE YOU USING FRESH MIX ?
HAS THE CARB BEEN OVERHAULED WITH A CARB REBUILD KIT - BECAUSE OVER A LONG PERIOD OF TIME
DIAPHRAMS ETC BECOME STIFF AND NOT FLEXABLE AND WILL NOT REACT TO PRESSURE AND VACCUUM IMPULSES FROM ENGINE AND WILL ACT AS IF RUNNING OUT OF FUEL?

IS COMPRESSION GOOD ?

IS SPARK GOOD , CONSISTANT ?  IF NO SPARK CHECK KILL WIRE MAYBE GROUNDING SOMEWHERE ? , THEN IF STILL NO SPARK  CHECK COIL ,   SPARK SHOULD JUMP A  6.00 MM GAP WHILE UNDER COMPRESSION LOAD  IF IT IS OK

DOES ENGINE RUN ON MIX STRAIGHT INTO CYLINDER THROUGH PLUG HOLE  Y/ N ?

DOES ENGINE RUN WITH MIX STRAIGHT DOWN CARB THROAT Y/ N ?

IF IT DID NOT RUN ON FUEL MIX DOWN CARB THROAT   AIR MAY BE INDICATED WILL NEED TO PRESSURE AND
VACCUUM TEST POWERHEAD TO FIND AIR AND VACCUUM LEAK

BE SURE CRANKCASE AND BARRELL BOLTS ARE TIGHT AND POWER HEAD HAS NO AIR LEAKS
BECAUSE ENGINE NEEDS AIR TIGHT C/CASE AND CYLINDER TO OPERATE CARBURETTOR FUEL PUMP AND METERING DIAPHRAMS

IF THE UNIT RUNS GOOD ON THE PRIME YOU GAVE IT  THEN A FUEL PUMPING / METTERING PROBLEM EXSISTS
PULL CARB AND REBUILD WITH CARB KIT

CHEERS LET ME KNOW IF HELPS


PAUL