FYI, I just finished a week of riding in southwest Colorado. Great fun. Highly recommended. Coming from, basically, sea level here in Illinois to an average elevation of 10,000 ft in Colorado, I had to change my jets. On my Mikuni pumper I went down two jet sized from 140 to 135. Bike ran great, but, of course, was lacking some of it's sea level power. At the highest pass (13,000+ feet) I did hear a couple of missed, but that was it.

I used a rule of thumb I found on one of the forum threads: Reduce your jet size by one size for each 5,000 feet of elevation gain. Worked for me.

 

If you do that often you should consider leaving in the lean jetting and adding a Dial-A-Jet fuel adder. Very popular with ATV and snowmobile people. Works similar to a Mikuni powerjet, but atomizes the mix by adding air. Tested by MXA and some other media and used in some trick carbs from Dick's Racing and some others.

I've run one in my 650 since around 2000 covering from sea level to about 5000 feet, temperatures from 18-95 degrees F and some hop up work including a full exhaust without any change in jetting and without issues. In my 250 CV carb I did the KLX300 stuff including the needle on second groove from top and a 125 main, working well at 900 feet so far.

Just a thought.

 

Not planning to. Been. Done.

 

On both my OEM carb and now with my 36mm pumper, I find the needle position to be more critical. I'm at 1700 feet here at home, but as I get to 10K mine stumbles rich even with a one step leaner main jet. When I drop the needle one notch for leaner operation, it's just about perfect.

oldad...SW CO...13000+ feet...Imogene?

 

Yes, Imogene, Cinnamon, Engineer, Black Bear, Hurricane, American Flag, and maybe Taylor passes.

I wasn't the navigator, so am not too sure exactly where we went.

The steps around the curve coming down from Black Bear Pass certainly was memorable, though. It actually wasn't that bad, but sure did intimidate most riders/jeepsters. The trail wasn't too bad. It was just the 1000 foot drop off the edge of the trail.

 

LOL!...yeah, that's definitely a "watch your left" section on Black Bear.

 

After years of hearing that Black Bear was dangerous and required a CJ/wrangler/ to negotiate, I went ahead and ran it with my Jeep Grand Wagoneer, lol.. I'd had the thing over all the others except BB.. No problems getting down it (It's a one way only trail).. The steps will leave a lifelong memory though.. If they'd been wet, they woulda been really scary.. I was surprised to see that there's no scary, "edge of a cliff", drop off at the steps, but the hard right just after them does offer a fall that'll ruin your vacation . Went into town for fuel, asked the attendant if my Wagoneer could do BB, as expected he said no, only "real jeeps" can do BB..LOL

 

Yeah, actually I think it's easier to do in a 4WD vehicle than a dirt motor. Depending on the year and conditions, the problem on a dirt bike can be loose gravel while trying to keep it slow and controlled in the gravel near that turn and at the steps. Otherwise it's just a "mind game" of steepness. I did it in a slightly modded full-size GMC Jimmy without issue, though a little wide for that trail. Speaking of wide and long, it really shows how easy it is when you see one of those tourist outfits with a Suburban equipped with those elevated seat rigs with about 8-10 people. Though not a death trap trail by any means, a fair number of people have gone off to the left at the right hand turn at the end of the steps.

About 4 years ago I came up behind two guys on big, loaded BMW GS models while climbing up to the pass from 550. After passing them, I just had to wait to see what they'd do at the steps. One guy actually rolled the whole thing to the bottom without drama. The other guy tumbled and couldn't pick up the bike. His buddy, me, and some guys on one of the tourist Suburban rigs got him upright to get him going. I cannot imagine wanting to do that on a big Beemer.

 

Kinda interesting, when I think about it, I can remember the tiniest details of negotiating the Black Bear "steps" in my beautiful Grand Wagoneer with the optional soft suspension and street tires.. and that was 1991! I did it with the parking brake set to where it almost kept the back tires locked.

Your take on doing it with a bike is very interesting.. It seems a heavy, "iffy tired" dual sport would be treacherous - Thinking about that, it seems logical..

All the years(summers) I've spent up there 4x4'ing - even trailering bikes every now and then - we never ran the passes on our bikes.. One year(1980's), I had a practically new XL600R that performed so badly (riding 2 up) on a little trail ride we took outta Durango, I sold it on the spot to a "native"...

 

Yeah, on my dirt bike vs. 4WD comment, it was just that a 4WD can go as slow as required regardless of fine gravel and sand on those steps, whereas you have to maintain at least a little constant forward motion for stability. Again, different years presented different conditions from what I noticed. After a bunch of 4WD vehicles kind of grind up some dirt and rock on the steps, it gets a little "skatey" at times...not unrideable. I've seen it the best conditions right after a good rain but before a bunch of vehicles run over it. It is one of the prettiest pass descents around.