Thanks Oz, I should have said that the inverter does pulse the compressor. It tries to start it a few times, then decides that It can't do the job. So I will use it for the other shed loads and keep the generator tuned to run my welder and air compressor.
Like you say, 2000 amps is pretty heavy going. Guess the batteries can't supply the current either.
Even if the compressor is only drawing 6 times the run current to start it will still be in the 900 amp range required from the battery. Oh well, still it is a good inverter for all the other stuff I run.