They reccomend the autolite 3922's which seem to be just about unavailable as a starting point. I'd like to go with a colder plug . I'm assuming that would be the also unavailable 3921 or 3920. Anyone have any experience with other plug brands?
I recommend ngk R5671 A-9 or A-8...9 being colder than the 8.
If it's a small shot (125) then the 8 should be fine but needs to be checked...after the run inspect the ground strap and there will be a discoloration somewhere...if it's near the bend then it's the right heat range...if it's close to where it meets the plug base then it's too hot.