I'll make the same statement here that I made on advrider.... after looking at every piece of hard information (service manual, owner's manual, parts catalog, brochures, Yamaha web site, etc.), I can find nothing that would indicate the bike has a knock sensor.
As to the idea that the bike is just generally so good that it can run on anything -- despite Yamaha saying it needs premium -- color me skeptical. I don't think Yamaha would specify premium if the bike had adequate knock margins for its anticipated operating envelope with regular gas.
I'm not aware of any way to specifically detect knock without a knock sensor. Doesn't mean it isn't possible, but I'm somewhat skeptical of this too.
It is important to note that engine knock is not something that happens all the time when you burn sub-standard fuel. Engine knock typically occurs only in "worst case" conditions - big throttle openings, heavy loads, low RPM, and high ambient temps. Most of the time - especially with big/powerful bikes that typically use only a tiny fraction of their available power - the engine doesn't need all the octane you feed it. It's there so the engine doesn't knock in worst-case conditions.
Also, due to tolerances and sample-to-sample variation, engines vary tremendously in their propensity to knock. As engines age they tend to wear, retain carbon deposits in the combustion chamber (which raises compression ratio), and just generally lose tune. This tends to increase octane appetite as the machine ages.
So engine knock is a highly variable thing, not cut and dried at all. Its quite possible to use regular in a vehicle that specs premium and never have any issue with knock. It's also quite possible to have an engine that knocks even when running the specified fuel.
If you know what engine knock sounds like, it's usually possible to "ride around" engine knock by going slower and using more RPM and less throttle. And you can pack octane booster, although I've personally no experience with how or whether it works. Cheap skates can use regular and if they restrict their throttle to 75% or so, never have any issue with knock. But it's not much fun buying a fast/powerful bike to go slow and save a few pennies a gallon at the gas pump.
All this being said, I do think the GS has an advantage in this area if you're talking about third-world touring. But if I were doing this sort of touring, I wouldn't get a S10 to begin with - I'd get a KLR or DL650. For my riding (adv riding in the forest roads out W), I'm sure I'll occasionally refuel at stations without premium and unless the bike is a bad knocker (which I don't expect), I'll just monitor how it runs on regular and adjust my driving habits a bit. No big deal.
- Mark
