Hey C-Trout, On page 18 of the Dolmar 5100/5105 repair manual it's showing that .25 mm is the correct gap. I think .25 mm is about .010 I'm thinking a business card might be more accurate or dig that feeler gauge out of the bottom of your tool box. Makita makes a setting gauge (944 500 891)that will put you right on the money. Download the 5100/5105 repair manual. It's free and it's a keeper.Just click on the link below. If you like the repair manual send me a one word reply back "Jackpot"I slipped a piece of typing paper between the coil and magnet to set the spacing. I hope that is right.
http://henigins.com/yahoo_site_admin/assets/docs/DOLMAR_PS460_510_5100_5105.170101754.pdf