Parts manual for a Stihl weedeater fs45

Question edited for clarity - maker name. No idea what you mean by a 'cruses shaft'. FULL 'make model (what is is)' in all questions please.

Here is one versus the other. I would think shaft swapping was fine.

https://www.google.com/search?q=Stihl+fs38+v+stihl+fs45

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crank seals may be bad. or flywheel key is sheared

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

most times it is easier to do just that

It appears yours has the integrated handle so see if this helps.

http://i1329.photobucket.com/albums/w548/ke4avb/FS45%20Throttle_zpssykehory.png

http://www.stihlusa.com/WebContent/CMSFileLibrary/instructionmanuals/FS-45-46-Weed-Trimmer-Instruction-Manual.pdf

STIHL FS 45 Google Search

Stihl FS 45 Trimmer Parts

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.

repair shop shortened shaft just a touch to take up slack in drive cable

you need to reset the carb. a and b screws