Spent a few days of high altitude exploring this past weekend in the Rockies near Taos, NM.
I was anxious to test my 390 above 10,000 ft. elevation, see how it performed. Made it past 12,000 ft a good bit.
Its a bit risky to explore so far into the wilderness completely unsupported......but I like it. A real free feeling!
Was not without some tension.....like when I got swallowed by this cloud as it passed over me. I stopped, dismounted, and threw a rock up into it, as soared by me. But, I never saw the rock come back down! I kid you not. That was weird.
Found my new campsite way above the bug line:
Now....about the performance:
My 390 definitely felt down on power compared to Rancho Highfive at 700 ft. elevation. That was somewhat expected, even with the fuel injection. However, I still had plenty of power to do the job any way I pleased.....when the bike was running. But I can sure see why the Rocky residents would opt for the 570 instead.
LOST....listen up! First day out, my bike would not restart after shutting off.
This began occurring after some lengthy...heated....long steep climbs. Felt like it was flooding out (at first). Then, maybe starving of fuel....I donno. After dinking around with it staring....probing...wiggling.....praying, she restarted and seem to run fine. Until the next time I shut it off. Repeat same scenario....over and over. Seemed it would restart after about 15 minutes of rest (and cooling). Sound familiar?
I incubated on this problem in my hammock overnight. Then, had my "Ah-Ha" moment. I took off the gas cap, turned it over, disassembled, and removed the stainless steel "check ball" in the vent.
I know.....I know....many have said to "take that thingy out of there pronto". Well, I had never had a problem with it at home (below 1,000 ft. above sea level). I typically don't mess with something until it causes a problem.
Guess what? THEY were right. Remove and throw that little ball bearing as far away as you can. And, just stop falling down.....no more worries.
Here's the deal:
At high altitude, under heavy work, the fuel was boiling (even with the CYBORG DEI mod on my tank). Apparently, the excess vapor was pressurizing the tank enough to lift that steel ball bearing and block the hole. The tank appeared to be vapor locking and/or over-pressuring which was definitely affecting the fuel flow/pumping action. Either the bike was starving of fuel or flooding with fuel.....it was hard to tell, exactly. I think starving.
After removing this check-ball, the problem was completely solved! I never had the issue reoccur....even during periods when I could hear the fuel boiling furiously inside my tank (upon shutting the bike off). This...when above 12,000 ft. It would fire right back up, on demand, every time.
The symptoms appeared to be clogged fuel injector.....clogged fuel line/filter.....failing fuel pump, when in reality, it was simply locking up the tank vent.
So, my question to LOST is: Have you removed the check-ball in your fuel tank cap?