Change yer FILTER!

[China Greg]

I've had two 1st Gen. B12's now.

It seems to me that these bikes are very sensitive to air-filter cleanliness.

I discovered this a number of years ago while riding my red bandito to New Mexico from New York. As I went farther and farther West, the bike started running increasingly rich.
I DID check the air filter. It looked clean enough and certainly viable, (to my somewhat experieced eye).
I even took the carbs apart in BLAZING-hot, Kansas rest area and bumped the needles, (leaner), and it was ...slightly better. Couldn't figure it out... the filter showed no signs of being clogged.

Finally, I pulled into Santa Fe during a terrble lighting/rain storm, where i pushed the bike mercilessly for hours. In the morning, the bike started up with a huge belch of black smoke, and ran like dogmeat. The "mechanic" at the local Soozook shop talked vaguely about "a valve job". I tried running the bike without an airfilter just for laughs... wouldn't even start.

Distraught, I plugged onward to Colorado Springs, where I changed my tires and found new air filter at a great, friendly Suzuki dealer. I was getting desperate, and finally, north of Denver, installed it.
BOOM! night and DAY!! the f**ker SCREAMED northwards. After that, the trip through S. Dakota (including Sturgis, One Week After the Fact).. and over the top of the Great Lakes through Canada and home. A total blast. Good ol' Bandit.
The thing was, the new filter wasn't THAT much different in color than the old one. Deceptive.

Just the other day I RINSED my current paper filter (yes, with water...no scrubbing though) and carefully blew it dry. (I'm too poor right now to buy a new one at $37).
Suddenly, the bike LAUNCHES through the upper midrange.

Clean yer FILTER, boys.

[303LURCH]

I wonder if your bike also had some altitude sickness and/or some bad fuel.  Santa Fe is 7000ft, Colorado Springs is 6000+ft and Denver is 5280.  As you go North on I25 you drop in elevation.  If I remember right, the needle helps in the mid-range.  Jetting for sea level and a dirty filter I can see you having problems.  I have a 1st gen 1200 as well that I bought used.  It's seems to be jetted perfectly for out here.  I've riding it to the top of Mt Evan 14000+ feet with no problems.

[China Greg]

Mt Evans, eh? Rode my trusty GS1000E up that while touring with the Grateful Dead in 1981.

Both of my bikes were jetted precisely for about sea-level + 300 feet, using Ivan needles, Yosh exhaust, and modified (holes-drilled) airbox.

I've been on various long-distance trips (with both bikes, totalling about 60,000 miles)... as long as I have the filter clean, she'll go anywhere like a.... well a BANDIT.