There are two plugs for my '97 750 mentioned in the manual: stock and one range warmer. When I got new plugs from the dealer, I was given the warmer range plug (an 8 instead of a 9). I suppose it will be OK as I don't race or flog it, but would sustained touring at 90-100 do any damage, in your estimation? Actually, I've never had any low-speed problems with the stock plugs. TIA
The stock plug should be fine. The colder plug is for high rpm sustained running. Such as, track days, racing, and maybe those high speed runs of yours if thats all you do. The down side to a colder plug can be fouling, hard starting when cold (assuming you may live in a cooler area), and a slightly rough running engine until its warm. Now should you live in a hot climate and your motor runs hotter and you get into detonation (knock) a colder plug and higher octane can help that problem. On the other hand, one heat range is not all that much and probably won't make a difference either way. My suggestion, stick with the standard plug.
