odd problem developing last few weeks, when I increase oil/fuel mix to anything more than 40:1 timing gets all messed up and is misadjusted, this happens long before the plug fouls. this has happened twice so far in the past two months and I check the points this time and they 'look' ok but are now refusing to open and close when the magneto is turned so i need to replace them. I don't have a puller so is there any improvised way to replace points or remove the magneto cover without a puller?