Most portables are 2vac motors and a pump, the standard is 2 X 3stage vac, standard pumps used to be about 100psi to 135psi nowadays quite a lot are a bit bigger.
Thats about all thats in them thats servicable, then theres the electrics, plumbing and body none of wich need touching untill they wear or brake.
I have replaced both vac motors and pump in my machine, not down to my own use but as i brought used machine with a lot of hours on it, it had allready been put through its paces.
To replace vacs cost £130 each fitted, about £100 if you fit yourself.
Pump £181 fitted, about £140 if you fit yourself.
These prices include vat, if your vat registered its even cheaper.
Price quoted to get machine serviced around £200
