Thanks SSD! Regarding my original comment: I once stood fireguard on a starting Yak52 on which the prop when starting only went partially round and kicked back again (with suitable wheezing noises). The pilot then asked me to give the prop a shove in the right direction after which a normal start could be accomplished. After reading your post, am I right in assuming that this could be a case of a wrongly positioned prop? Does it feed air to all the cylinders at the same time (surely some will be on a compression stroke and won't benefit from it) or just several chosen ones? The aircraft had flown that morning just a couple of hours previous so there was no reason to pull the drain plugs I'm guessing.