What Spark plug do you use for a FS45 trimmer

hi try here hope it helps https://www.scribd.com/doc/190134377/FS45-Service-Manual

over fueling

http://www.mediafire.com/download/fmfdwlul7fbdw2y

NGK BPMR7A spark plug

Yes it could be.You can purchase an inline ignition tester from your local parts store and test it. Its also possible the plug is fouled.

Check the timing gap between the ignition module and the fly wheel.

No, I'm not sure why STIHL even makes curved shaft trimmers at all. I have never worked on ine in 10 years of being a STIHL tech, I just throw them out when they don't work and steer the customer to a straight-shaft. It's their punishment for the mistake of buying the curved shaft in the first place.

This model is the closest this site comes to the model you have. it should help as diagrams should be in the manual on later pages. You will need Adobe Acrobat Reader as the manuals are in PDF form:
http://lawnandgarden.manualsonline.com/manuals/mfg/stihl/fs_55.html
Please vote on this solution.

has it got compression? does it have spark to? need to check b4 go further....