what i would like to know if i were to open a repair shop do you think expats would come to me being a westerner as no doubt some expats would have had bad exsperience with the local computer repair shops
Maybe, maybe not. It would depend upon how good you are, your prices and location.
Don't forget that some of us have had bad experiences getting our computers fixed in our own countries. I have, (a long time ago), until I learned how to "build" and repair them myself (desk-tops).
I still repair computers sometimes, but I do it for free (unless parts are involved).
There are literally thousands of retail computer outlets in Bali and many of them have their own "technicians". Like anywhere else, they're not all good, but some are excellent by any standards.
If and when I can't be bothered fixing one of my own (or become stumped), I defer to a particular place in Gatsu (Jalan Gatot Subroto).
In more than 15 years, I have always found them to be honest, efficient, never over-charged me for anything and the main guy speaks good English (a bonus).
Personally, I doubt that an expat could realistically set-up a profitable computer repair shop in Bali.
I'd be happy to be proven wrong.