The homemade air compressor I bought for $12 at an auction not long after moving here gave up ghost couple years ago. Electric motor seized and the compressor was an old truck air brake compressor and wasnt ever very strong. I've gotten by with tiny "emergency" compressor that came with some junk car I bought long ago, but need bigger more durable one. I've been thinking of replacing motor and compressor on the homemade one with a 5hp engine and an old York air conditioning compressor with oil resevoir (have two or three good Yorks setting around that will never be used again). I thought engine instead of motor cause I have couple spare 5hp engines but no spare big electric motor. Thing is how is pressure cut out handled on an engine driven compressor? On an electric, a pressure switch just cuts current to the motor. On an engine driven one, you wouldnt want to kill the engine ignition, as you would have to restart it again manually. I suppose an electric clutch like already on air conditioner compressor, but then there would have to be a battery and a way to recharge the battery unless I wanted to use car battery every time I wanted to use air compressor. So how are small commercial engine driven compressors cycled? Some sort of pressure release valve that keeps tank from being pressurized beyond a set pressure?