If you are going to do this sort of work, go to the Walbro site , download their manuals and watch the videos.
Joe Pace did a series "2 stroke diagnosis" watch them all and take notes.
Very important is his approach, where to start how to start & what order to do things in.
This is very important, a systematic approach or you will end up fixing a lot of things that were not broken, till you pulled them apart.
Cost will blow out, customers will not pick up their machines because it is cheaper to buy a new one.
THERE ARE NOT MAGIC SHORTCUTS other than experience and a skilled ear which takes time.
While I have been playing with vintage motorcycles for 40 years so was mechanically competiant, I had done SFA with mowers before I bought the business 4 years ago.
It took better than 2 years before I spent more time with the machine than with the computer.
I can say after watching a lot of EWE Toob crap the 90% of what is there is rubbish posted by ego maniacs with little to no knowledge of what they are doing and even less about teaching. ( I did adult education )
This one is really good on both counts
Donyboy
As it this one who takes the different but well proven humour approach
https://www.youtube.com/channel/UC2Cd9kKYXFakV7ChvU_rjKw
Get some coffee and start watching