Where can I get a parts manual for a 1997 Lesco 48' walk behind?

Look on lescos website

you could go to walmart or go this link
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Be sure your petcock is in the open position. Not uncommon to forget to open it after working on the carb

Consult your service manual.

usually the only safety is the engine shut down control cable that is attached to a smaller handle on the main handle that you must hold to have the mower to start and run part number for the cable is 946-0957

Dear Sir:

I recommend you to RUN the software callibration for easy diagnose and troubleshooting, and fix it.

The elevation motor can be adjusted such: potentiomer in the motor.

Do not waste your time. sincerely God bless you.

Here's the manual!
http://www.lesco.com/content/cache/Unity/ProductCatalog/Files/PartsSchematic/706658R023AC.pdf

good luck buton went out of bus a long time ago you can try Jacobsons web site they now own them