I am in the second hand market
When I check out the sp 140, aside from the accessories and how clean it is and that it works, is there anything else I can do, ie self diagnostic tests, etc?
When checking out a gas one, I would get a mechanic to look over it, would that best to be a normal mechanic, or a motorcycle mechanic
Any other tests I should do?
Many thanks
Paul
I’m not sure where you’re located, but if you have a PPG school near you then I would recommend signing up for a training course and then having one of the instructors check it out with you – maybe having the seller bring the unit to the school. And of course tossing some bills to your instructor for their time and expertise.
IMHO, there is a lot of benefit to having the instructor take a once-over to notice items that might easily be overlooked by a mechanic who, I presume, is mainly going to be evaluating the general motor condition. As far as the type of mechanic for our craft, the gas ones are all almost universally 2-stroke – So you’re looking less for a car or typical street bike mechanic and are more looking for a small engine mechanic/specialist. I can promise you, any decent instructor at this sport is already moonlighting as a small engine specialist. 
But there is also the frame, harness, prop, and all the little fasteners and other details to account for in the safety and value of the unit. Well worth the proper guidance; again just my $0.02.
As far as the electric side of the coin, it should be pretty straight-forward to check if it’s in decent condition. If everything powers up without fuss and spins as it should, then you’re likely golden. The v2 version of the battery (the ones with a toggle power switch on top) have a BMS with Bluetooth, which allows you to connect to the battery with an app and check on some health conditions that way, as well as the number of cycles it’s gone through, etc. I don’t believe there is any equivalent way to get info from the v1 batteries beyond tearing into things, just plugging it into the unit and checking that everything checks out on the display and provides the output it’s rated for.
And there are some health checks / diagnostics that are performed on startup, as if certain parameters are out of range then the unit won’t arm.
I’m not aware of any manual “diagnostics” that you can trigger on these units, but if it exists then I’m sure one of the smarter folks will chime in with the details.
Good luck on your purchase, these things are a blast!
I’m in Australia, so similar time zones are New Zealand, Vietnam, Laos, Cambodia Phillipines, Malaysia , Myanmar (Burma)