the whit 990 had a butterfly type screw on the pump which you unscrewed/ screwed? in/out to give excess fuel or was it to alter the timing. eithe rway it worked.I'm not Polish but we used to have a white DB 990 which was a bit dodgy in the cold. I had a rag dipped in diesel on the end of metal stake which was lit for this purpose. Helpfully there was threaded cap on the intake manifold which would suck in all the flames, put out the fire and start the engine in one go.