Who rode an ATK back in the day?

I raced one at Carlsbad. 1987 CMC Transcal if I remember correctly. It was a fun bike. Super light feeling. easy to ride, but hard to ride fast. Seemed like you had to be very deliberate with shifting. I would buy one if I found one that was affordable. 

I rode one at Perris Raceway around 87 or so. It was the best suspended bike I have ever ridden at the time.

The 406 was pretty mellow for a 406, not much more than a good running 250cc. But to be honest, I was racing a Honda CR500 at the time, so.....

Had a 605 dual sport.

Awesome power and fun to ride. Electric start and all. If i remember right it was 270 lbs, which is comparable to the ktms the same cc now.

I bought it to use a lot moving equipment around the charlotte area when i ran races. I would put it on the teailer with a dozer/tractor and ride it home to get another truck.

A couple hour long trips on i 85 with that ribbon of a seat and the vibration of a big single at 65 mph had me swap it out for a klr 650.

If the ride home had been 45 miles of single track, or even fire roads, i never would have sold it.

I saw several people running area LL qualifiers in the four stroke class back in mid/late 90s, turn signals and all.

I had a 406 for a little while. It was really good on hardpack and on rocky trails. It felt very light and stable, but didn't turn the best due to being a little bit tall feeling. 

A buddy had the 406 and I rode it every chance I got.  It really felt light underway but the clutch and shifting weren't up to Japanese standards.  The powerband was also pretty narrow but power was decent when you were in the meat of it.  It was also drop dead gorgeous compared to my Honda's. I'd add one to the collection in a heart beat if I found the right deal.    

The 250 was good. Unconventional but still a good bike. The other ones where a little quirky.

I rode one for a little while, even had a friend that I went into business with and we sold a few.  It definitely wasn’t a beast.  It was tough to compete with open bikes on the start but after that, it was really good.  Smooth power and great suspension and handling.  Maybe the best rear suspension I ever rode.  Rear brakes were an issue.  They worked but I’d go through a set of pads in an hour.  I’m a brake dragger but that was a bit much.  

I raced the Unadilla National on it, and it was cool because enough people recognized it as an American made bike that I could hear some cheering despite being a back marker. I’ll attach a pic jumping out of gravity cavity.  It was October and I was wearing a sweatshirt and a Link Drink for those that remember them (I was mostly a scrambles racer by this point ).

Very cool. 

I had a 406 for awhile. Super linear power. Nice suspension. But, it was tall and the brakes were horrible. Fun bike for the time. But, I switched to a Husqvarna 360 and was much happier.

I owned a couple liquid 250s . Utah ATKs without the atrak system so some would say not real ATKs . They were fun on the trails , not so much on the track . Unfortunately I've never had a chance to ride an atrak ATK .

A friend of my dads had one and I always wondered what the logic behind the rear brake on the counter shaft was all about. 

Wasn't that to try to reduce the amount of "unsprung weight" on the bike?

Zitterkopf (sp) liked his 604.

Maybe part of the reason the rear suspension absorbed square edges like no other.  Also, the chain torque elimination system.  No linkage either.   The downside was not being as effective using power to stiffen the suspension or seat bounce.  

Less unsprung weight I suppose.

My friend had a 406 and one of the liquid cooled 250's. His biggest issue had with the 406's nickel plated frame. Had problems with the frame corrosion and it cracking. 

Didn't like the counter shaft brake swapped it for a more regular setup. Said the 250 was tall. 

I have a '90 250 and spent a bunch of time on a '88 406. I was a brake dragger so the rear countershaft brake did not work for me. I would overheat it and boil the fluid constantly. 

I had a 406 for a while. Handling and suspension were both pretty good. I remember the welding on the frame and swing arm were excellent. The two things I couldn’t get used to were the rear brake and the narrow power band. The brake pedal pivoting the opposite direction from any other bike was hard to get used to. The rear brake was also very weak and went through pads quickly. For an open bike the low end power was pretty weak. I remember clutching it more like a 250.

I bought a new 406 to race off road. First desert race the shock shaft snapped in half on the bomb run sending me to the hospital with a broken hip. Bike cartwheeled and was pretty ef'ed up. ATK took my bike back and made it new again for free. Six months later when I could walk again I sold it!

Here's the bike they had ready for Brad Lackey for the 83 Carlsbad USGP . He chose to race a YZ instead .

There was also a pretty big attempt in that era to eliminate rear end chain torque standup under rear braking to maintain compliance in braking bumps. The Yamaha BASS system was also a bad attempt to fix that issue.

ATK had anti-torque devices in both directions, with the countershaft rotor and parallel chain path no longer applying swingarm torque that stiffens the rear during braking, and an optional chain tensioner system removing squatting loads under acceleration.

I bought a 605 in 1993.  When it finally arrived (I had to order it) they told me it was likely the last one of the California production line prior to the move to Utah.  I loved that bike and still have it.  I also seemed to have a lot of success with it but likely couldn't do the same things on it today as I did then.  It took a fair bit of muscle to keep the thing going, and I don't have that today.  Frankly, I'd be impressed if I could successfully start that sucker today...

Stumbled across this photo this morning and remembered seeing this thread recently. My dad was an R&D engineer for ATK back in the day and often shares fond memories from that time. I’ve always thought about picking one up for him as a gift. He’d think it’s bitchin