i had a necchi for a long time and it was reliable as could be and easy to maintain. i also took it apart and put it together myself. it's a basic machine. there's not much to break. it sounds like the timing may be off just a little. if you have the manual it will show what it should look like. check it out.
running it full force is a good idea. never thought of that.
i ran mine til the brushes needed replacing for the 2nd time. it ran very slowly at that point. then i put it out to pasture (a friend took it to her vacation home).