spark plug heat range

Aug 7, 2005
I recently tried a set of Autolite AP64 platinum plugs in my 850 Mark II and was impressed with how well they masked my timing and carburation issues. However, I'm not sure if they are the proper heat range and wonder if they will cause problems later. Anyone have any experiance with these plugs?
Apr 7, 2004
I still run them with no ill effects even after long highway runs at 80 MPH 4250 RPM on my bike. I do a fresh set each year mainly because of the crummy black oxside finnish. Only you can do a high speed plug chop on your bike to know your bike. They are not all the same even in the same city on the same gas. Bosch WR7DP's are safe for sure and a smoother but weaker idle. I orded a set of WR6DP's and they are way cold for Nortons. Most people don't read plugs right read here first. Unleaded gas changes the info you get reading plugs. You need a working kill button for this. ... plugs.html