<!-- from fixya rte -->How do I replace Stihl br550 push rod - Stihl Blower Air Filter Br 500 550 600 4282-141-0300

When the paper bar code sticker is worn off, you can remove the engine shrouding (orange) and it will be located on top fin of the cylinder just before the spark plug hole.

I’m happy to assist further over the phone at https://www.6ya.com/expert/rolandw_c013176d62ee17ae

Gain access to carb and right by the bulb you will see about 4 screws holding down a metal plate that holds down the primer bulb. Remove the screws and plate and replace damaged primer in same spot, and screw plate back on.

fuel filter or fuel pump

take out the spark plug and try turning it over

sounds like too much oil inside it
can cause compression issues
drain clean the oil
you can tell lots with no plug in
could be anything in the transmission to the trimming head
perhaps the clutch is seized up

the seal is missing youve dropped it in a garden somewhere
you need a new one
try ebay
but i will tell you stihl is VERY good at service parts
and very helpfull

http://www.ebay.co.uk/itm/PETROL-FUEL-TANK-CAP-FITS-STIHL-BR500-BR550-BR600-BLOWER-/141346840553?pt=UK_Home_Garden_GardenPowerTools_CA&hash=item20e8ed9fe9

fuel filter inside the tank and inline
bad start stop switch
bad carbiration
bad spark plug {burned}
bad ht cable
bad magnito coil

take your pick and rull them out one by one

the return spring is shiered up
you need to replace the rip cord cassette or change out the spring
i would ask around the local service guys if they have a spare return spring also the two 'pawls' could be badly worn and need replaced

there is a key way built into the flywheel... it keys into the crank... no other way... but aligned with what ??? if you do not physically see a key way then did it shear off ???

fuel tank vent
bad inline fuel filter
leefs inside the tank flush it out
bad plug replace it
bad air filter replace it
bad pickup ignition coil

oil level too high or low take it all out and measure what you put back by the user manual from the stihl site {use google to find it}

http://www.h-machine.jp/part_list/stihl/stihl_BR%20500,%20BR%20550,%20BR%20600.pdf

Sorry its in Japanese but the part numbers are the same. :)