I used to do type-conversions for glider pilots in a Motorfalke motor glider. It had a very reliable VW-conversion, with electric start, that worked first time, every time, provided you remembered to pull the choke out, if the engine was cold.
However, as part of the conversion process, we were required to do dive starts, in case the starter had failed. To start the engine required a very alarming nose-down attitude and a speed of 70-80 kts before the prop would turn over. I vaguely recollect that the height loss was more than 1000'. Vne was 100 kts.