Originally Posted by gkamysz
It sounds as if the ignition may be firing early even tough it should retard to just before TDC. I think some or all of the DLE 20 have a strange timing curve?
If I had to estimate that cranking speed I would say somewhere between 400 and 600 RPM.
If the engine is using an "RCexl-like" ignition, the retardation only takes place above 400 RPM. With a slow accelerating starter that means, the engine will start igniting before a sufficient speed is reached, and than timing will be too early, and the backfiring will prevent the starter from reaching sufficient speed.
So IF my suspicion is correct regarding the type of ignition, then first cranking up and only activating ignition if sufficient speed is achieved, would be the most logical solution....