How old am I? Well, let's see, I was about three when president Lincoln was shot, or was that Kennedy? :-) Will be 50 the 1st of next month, old enough to make plenty of typos, that should have been 1997.
I didn't mean to imply that single cylinder dirtbikes could or should always beat multi-cylinder street machines, especially street twostrokes. The newer 4stroke streetbikes such as the ZXR 600 will do in the tens for instance. However, they have been receiving tons of R&D whereas the open class 2stroke dirtbikes have received none for many years, unlike the 125s and 250s. 55-60 hp for a 500 2stroke MX bike is pretty low compared to what the 125s & 250 2strokes currently make, proportionally. Just meant to point out that often, a change of gearing will increase acceleration and can be an improvement in drag racing situations from stock motocross gearing.
By the way, Opferman, did you really mean to say that the stock-geared '83 Maico 490 would do 115? You must mean the Sand Spider, rather than the motocross version I'd think. The '81 490 my friend had would do around 80 more or less, as geared. Perhaps the guy he bought it from had lowered the gearing, but if so, he didn't ever mention it. The KX 500 stock only does 86 mph and the '84 CR 500 my friend had was about the same, stock.
Not all of the riding out here is sand. Much of it is loose rock, gravel and caliche. Hills like this sometimes have very loose sections with intermittent outcroppings of rock ledges so you go from spinning out, to sudden traction. Especially around the mountains, Mt, Franklin, the Organ Mts, East Potrillos, Mt Riley etc. (Some of those areas one can no longer ride anything other than a mountain bicycle now). In those situations, I know well the problems you described on the CR 500, having ridden my friend's ''84 model. At that time, I had a 1982 Yamaha IT 465 which had a powerband very similar to your Maico or KTM. The IT did great on those type of hills, the CR was downright scary on them. The IT could lug up nearly anything. The CR had the power, that wasn't the problem, it was that it was explosive and would spit you off in a heartbeat or loop out if you backed off the power then rolled the throttle back on. If you backed off very much, it would bog. Clutch it to get the revs back up and you're gonna loop it. The older Maicos would be very good at that type of climbing. The Maico my friend had in '97, I never got to see ride in such conditions. I could only watch by that time, an accidental gunshot wound left me paralyzed from the nipples down, partially disabling my right hand as well, back in 1991. So, by that time, I was brought along to wherever they would ride and I'd just watch and have a few brews. Those times the hills were mostly sand where we went. The CR 500 loves those type of hills and with good rear tires and proper gearing, eats them for breakfast. My IT did not like the pure sand hills nearly as much when I could still ride, neither did my brother's modified Yamaha TT 500. Both tended to dig in more whereas the bikes like the CR and KX 500s tended to skim along the top surface of the sand. My brother rode the 81 Maico a few times and said it reminded him of my old IT 465, power wise. Similar powerband but more of it. And of course, the handling was far better on the Maico. My IT handled like a tank. So I'm not entirely unfamiliar with more technical climbs like you describe, Opferman. More what I called "enduro" hills. Nasty things where the Maico powerbands make them much easier to use than the explosive KX or CR type powerbands, and I think I can relate to what you are saying even though it is very different terrain. The Maico has one of the best all around powerbands of any 500 dirtbike ever made, no argument there. Now having said that, I think, were you to find a long, steep pure-sand hill that none of them could make, an '82 KTM 495 or KX 500, or 'probably even your '86 CR 500, will get farther up said hypothetical hill than the '83 Maico 490 or the '84 KTM 495. I may be wrong, however, but judging from some of the tougher sand hills in our area that I've seen some of these bike make, that would be my guess. By the way, a couple of the hills I'm talking about, my brother's TT 500 Yamaha couldn't make, nor a mid '80s XR 600, both 4strokes. They'd bog in gears high enough to top the hills and would have to downshift and ended up digging a hole and sitting in it on the hill. My IT could, but not as easily as the CR 500.