Hey, Big Boar, that was an interesting post to me. You say you have a 1980 Yamaha YZ 465? Well, I used to own a 1982 Yamaha IT 465. If I understand correctly, it had essentially the same motor as the YZ but in a different chassis. A wide ratio gearbox and possibly a bit more flywheel, but for the most part, the same motor. I've wondered for a few years now how that IT would stack up against modern 450 4strokes in flat out drag races, throttle roll-on drag races, etc, to the slower bike's top speed. Also how it would stack up against them in climbing steep, sandhills. You seem to be able to answer that question.
According to modern motorcycle magazines, the newer 4strokes are putting out a bit over 50 hp on the dynos, the best like KTM, a bit over that, a few a bit under. I strongly believe the dynos now are giving higher figures than the ones I went by in the late '70s and early '80s. In those days, I went by the Webco dyno figures as my standard. According to them, the YZ465 was putting out right about 42 hp at the rear wheel. That would mean it is way down on hp against modern 450 4strokes, and even considerably less than a KTM 250SX or 2010 YZ 250. I find this difficult to believe.
I'm disabled now and haven't ridden in many years so I may be very mistaken. Anyhow, going by newer dynos, the CR500s of the 1990s were more powerful than the first two CR 500s, 1984 and 1985. Problem is, almost all the magazines said the 1985 Honda CR500 was more powerful than the later models and that they deliberately cut the horsepower back a bit in 1986 forward, to make the bike easier to ride and more friendly. The Webco dynos in those days had the '85 at just under 49 hp, and the '84 air-cooled one at just under 50. if you look at the dyno figures on newer CR500s which should have less power, they test at anywhere from 55 to nearly 60 hp. As a typical example, check out the two charts here on the DB Snorkel page on the two '93 Honda CR 500s. One of them has more torque on this dyno, than either the '84 or '85 CR500s had horsepower, on the Webco dyno of the time. I know for a fact though, that the '84 and '85 Honda CR500s were indeed faster and more powerful than any of the later year Honda CR500s with the possible exception of the '88.
http://www.thedbsnorkel.com/dynamometer.phpI remember my IT was very quick, deceptively so. It would effortlessly leave 250 MX bikes in the dust. I also beat an 850 Yamaha street bike through the gears on pavement several times in a row until I ran out of top speed. Could have easily pulled a couple of more gears and wish I'd had them, lol. Anyhow, all of this has led me to wonder. If I go by the new dyno figures and they are consistent with the figures that the Webco dyno put out for bikes like the YZ and IT 465s, then I'd have to conclude that the new 450 4strokes would simply smoke your '80 YZ 465 or my old '82 YZ 465. In fact, so would a new YZ 250 or KTM 250SX which put out about 45 and 49 hp on today's dynos, respectively. That would also mean that a new KTM 250SX has more power than the '85 Honda CR500! My gut tells me no friggin' way! The 450 4strokes might beat my old IT 465 in through the gears on a long straight with good traction, but it would be by just a hair. That's how I feel, but I've never been able to test that, and may be very mistaken.
I know they cannot beat my friend's old '94 CR500 Honda, which still runs great, and my brother-in-law used to have a 1985 Husky CR500 2stroke which he sold. Nevertheless the guy he sold it to rode with a guy on a CRF450 a few years ago and always just blew it away on the straights. So, my question is, is your YZ465 running good, and if so, can it at least stay even with the new 4strokes you ride with, in acceleration on straights? You mentioned climbing hills. Did you climb any they couldn't, or the other way around? Do you feel like your '80 YZ465 is lacking power compared to the modern big-bore 4strokes, or is it equal or better? I haven't been out in several years and the seeming discrepancies between older dynomometer readings compared to newer ones makes it hard to figure these things from where I am now. I don't care about handling or suspension, just acceleration and power. I was an off-road, mostly desert rider, blasting through the desert at high speeds, hard acceleration and hillclimbing were what I enjoyed. For fun, here's a different MX race with enduros competing on an MX track. The fight for first place is between a Yamaha TT600 4stroke and a Yamaha IT490 2stroke. --->
Yamaha tt600 v it 490 Part 2( With Sound Yeah Ha !!!)