I think I read many years ago an article about a drag race between a late-80's CR500 (w/street-tread) vs. a VFR 500 Interceptor. If I remember correctly, the VFR could outrun the CR, but only because it was impossible to control the CR enough to get a good run on the asphalt.
On a similar note- I've never been intimidated by any motorcycle.. except my brother-in-laws Kawasaki KDX500c 2-stroke. That machine hates people. Just kick-starting the beast can send you to the hospital. It makes my RM250 seem like a toy. I can't fathom winding that thing out without an ejection seat.
I've got an '87 CR500 with a clean-and-match port job, .80 over. Noleen modified forks & shock. 15/47 gearing. I've never had it timed, but it walked away from a buddy's 1 yesr old KTM EXC520 at 92 mph (per his speedometer).
If the CR rider would have started the bike in 2nd gear, I guarantee he would have won. If tuned right the CR accelerates like an F1 car. I know it soulds like BS, but I've never lost a drag race (in the dirt).
BTW this is the same buddy who traded his '91 KX500 for the new Katoom. I never reallly liked his KX, it always felt like you were riding an oil-drum with footpegs. Way too big.
Starting one is no problem, just get the kickstarter ratchet at the top of the stroke and KICK (prime it first with 7 or 8 real slow kicks). My CR starts on the 1st kick most times. if you follow the above drill.
But in consulting my well worn issue of the 1973 Dirt Bike Buyer's Guide, (that resides on the tank of my toilet, or "throne" as it were) it does indeed seem that there was an American Eagle produced in the UK, and everything (but the transmission) was a copy of the right-side shift pre-'71 Husky.
The American Eagle had a horrible reputation for blowing up BTW. It is also on the "10 worst dirt bikes ever made" list, compiled by Super Hunky in that same issue.
I'll take your word for it, but to the best of my memory (yeah like that works as well as it used to) American Eagle used Laverda and Bridgestone as their source of bikes. 1973 sounds like the right era , however. Does the article say who supplied the fake Husky?