That'd sure be worth a look.
Gents, I don't see why the KX couldn't be made into a very good pre75 weapon. Apart from the ugly colour that Mark mentions (which didn't help them sell), they look 'right' - right proportions, ergonomics, rake/trail, weight distribution, wheelbase, frame design etc, & as the saying goes w race bikes, what looks sight usually is right (or at least is well on the way to being right).
For my money, as much as it pains me to say so (cos I love euro-bikes) it looks more 'right' than nearly all the euro big-bores. Little wonder - picture a 74 TM125 tank & 400 Suz barrell (stroke only 1mm diff, but stud spacing quite diff) & spot the diff from an 74 RN400 at 20 paces!! The blood-line appears to me to be uncanny.
Seems to me Lackey & co proved their worth beyond doubt in 72-73. No doubt his bike was better, but the similarity to the prod'n bike is striking (& Lackey admits it in VMX # 12). His bike appears to be more or less a pre-prod'n F12M (which they only made about 200 of, but it was the forerunner to the KX & very much like it)
Of course, you'd have to junk the suspension. The 36mm forks should be pre-75 legal cos both the 73 F11M & 74 KX 250s ran 36mm forks. 35mm Betors are another nice option (which Lackey & co often rode with)
Personally I think the press of the day was scared of the 450 (based on their experience of the TM400 & SC500). I recall one test caption rang out, "Hey bike, come back here!" One or two tests read like what Mark describes above, but others were totally different. Ironically one of the former type reports was written by Ray Ryan. He likened it to a giant sized elsinore. The bike he rode was an ex Team Kaw Aus race bike, so who knows what might have been touched up inside. And by the time he wrote VMX #12 his description was markedly different.
The mate's one I rode was nothing like that. It may have been tamed by a heavier flywheel cos it was set up as an enduro bike & registered (it made a great enduro bike except for the down pipe, but even the g'box ratios suited enduros well). But I vaguely recall you only had to put a lighting coil under the existing flywheel to do that. (I'm trying to check part nos on that). With a g'box ratio spread of 3:1, top speed on an MX course should be little short of breath-taking if geared appropriately.
For what its worth, I'd have described the power much more like a tractor, as other tests of the day did, & so too did Jim Cooke in VMx #12. He apparently rode a box stock 450 in the AMA 500 championship one year w several top 5 placings. I vaguely recall photos of the day which would verify that (hammerhead shocks & all!). He was more a suppported rider than a full works rider like Lackey, Desoto & Weinert. Wyman Priddy did pretty well on one (stocker) too. By the time Weinert was on board (& Lackey & Desoto were gone), the bike he won the championship on (c 74? - pictured above in Marks post) was very diff to prod'n KX.
The porting specs of the KX are very mild w durations of 176 deg for Ex, 111deg for trans & a measly 142deg for inlet. That's trail bike specs! And look at that loooong pipe. It screams broad powerband. They simply relied on raw cubic capacity for power. The best description I think is Jim Cookes in VMX #12 (go read) - a tractor you could ride all day in 3rd gear even in fairly tight corners. Well, maybe thats a bit of hyperbole.
Seems to me they could be made as good as any euro big-bore of the day w a little work that fairly easily done these days. I know that sounds like heresy, but I always did swim against the tide if there was good reason to do so. The fundamentals are there. They were very light for their day too. Dare I say, they could have been a cheap-skates RN?? Alright, perhaps thats hyperbole too. (Pls don't tear me to shreds)
The 400cc version of this engine in 75 was a better engine w 1000 rpm more on top, & the barrell slips right on (but of course its not pre75 legal in OZ - it is in US), but that makes me really wonder about fitting a 400 Suz top end which would be legal. It shouldn't be insurmountable difficulties.
There are more of them around than you think - quite a few in Qld if yr moving in the right circles. (Brisk Sales sold quite a few, mostly as enduros w lights.) But I'm not sure they get taken out to play much.
Brian Cox raced one many times at the Nats. Anyone know how he went?
