Hello,
I am a happy owner of an Artes/TJT 3000 with more than 100 fligth.
I have a problem with the starter motor during the cool down sequence.
A strange sound (like the starter is less power) and the cool down
sequence need more time to complete than before and, the noise sound continue.
Maybe the battery is loosing is life time? or someting else?
Tkanks in advace,
Roberto Castellan from Italy, Ciao.

I'm not an Artes guy, but my first thought is a worn-out 'O' ring at the starter's cup.

I Agree with FILE IFR , The first thing I would investigate is the O-ring in the starter cup. The motor in the starters dont run long enough to get worn quick unless it stayes hooked to the compressor and runs with the engine which then turns it to a generator ..

pull the motor out of the starter bullet, and apply some power to it...if it still vibrates and makes noise, is likely the bearings are shot (it happens), if it is quiet, likely the o ring as suggested above....