I like the idea of restricting the vacuum supply to the decompressor better than trying to restrict air flow to the other side of the diaphram which gets mixed up with the compression gases. Are you sure its nothing to do with being slightly flooded? Thats the only time that it happens with mine usually when trying to blow out the system so that it will start. It usually will do nothing for a couple of pulls then kickback once or twice then start. Its not very often only when too enthusiastic with the primer bulb.Most of the time it starts pretty well but a heavier pull is needed compared to a ordinary PT. This one still has a basically unmodified carby too, just the kill switch disconnected. It was working OK so " If it ain't broke don't fix it" I have sent a modified carby with it but there has been no need to fit it.
I have never taken much notice of these decompressors. Always OK and left alone. the restrictor is in the end where the tube goes on I suppose.
