Although I have no direct experience with this coil I will tell you what I know in general. A spark plug gap of .035 will give you the best performance. Better mileage , more complete combustion, nicer idle, etc. Now the buts. If you are using a Boyer igniton it must have less than 6 ohms resistance. If you are not running a Boyer do that first. It must have enough voltage ( I think about 40,000 to 50,000). In my day we used the infamous K mart coil. Great voltage etc. How ever the amperage draw was so great that with the headlight on you had a constant loss electrical system. Gradually the bike would just stop running. I know that with the new electronics and such you can get around this issue but sometimes it may take more than just a coil to make it all work. Good luck.