I'm probably violating protocol here, but I'm going to duplicate a posting I just made in "Sever stumbling at altitude" so that relevant information can be obtained from this thread. I've made a few changes in this re-post.
I've have an 07 FJR1300 since Feb. and have put 20,000 miles on it. I've experienced many, many episodes of stumbling most of them associated with altitude changes.
Recent example:
During the Memorial Day 3-day holiday I rode from Seattle to Pikes Peak. I left work in the Seattle area about 3:00pm and rode (through the night) through WA, OR, ID, UT and entered CO on highway 70 from the west. At Grand Junction, I switched to highway 50 and made my way to Pikes Pike from the west, arriving at the park at about 3:45 CO time. After paying the fee at the gatehouse, I started up the Pikes Peak road.
The FJR didn't want to run under load. The speed limits on that road are as low as 10 to 15mph. I attempted to ride that slowly, but the engine kept dying if I let the rpms drop below about 4000. It would idle normally, and until I started engaging the clutch the engine seemed normal (sound, vibration, etc). But the second a load was applied, the engine bogged down and died. It took me more than 2 hours to go the 19 or so miles from the gatehouse to the summit. I did this by reving the engine to about 3500-4000rpm and slipping the clutch--constantly--to keep the road speed low enough to stay under the speed limits and make the corners. I had to stop, I guess, about 20 times to rest my clutch hand. The engine died about that same number of times. No indication from the instruments anything was abnormal--temp was always showing about 4 to 5 LCD segments. I think the park entrance is on the order of 7000ft; the summit is 14,110ft. Temp, if I remember correctly, usually was in the 50 to 70 range.
When I got to the summit, I had severe arm and leg cramps and a killer headache. I rested for a hour or so before heading down. When I started down, the engine seemed to work normally, that is, it would accept a load at low rpm and not die--but going down Pikes Peak doesn't impose much of a load on the engine.
During the remainder of the trip--up to Rapid City, SD then back to Seattle, WA, on highway 90--there were numerous episodes of engine surging: at constant throttle on essentially level highway, the engine would rev slightly, then stutter.
Other episodes:
This one I can usually reproduce at will, but not always.
I live near Monroe, WA; elevation under 100ft. I frequently ride up to Stevens pass, 55 miles away, elevation 4200ft. On that ride, say a 4100ft elevation gain, while riding up grade the engine often does the surge then stutter thing--at constant throttle going up constant grade, I can't keep the engine speed constant, the ride is very jerky no matter how careful I am to keep the throttle constant. Usually, when I turn around at the summit to head back down, the engine will not take a load below about 4000rpm for several minutes (this is in 1st gear). At constant throttle, say 3000rpm in 2nd gear, mostly coasting down the grade, the engine acts as though it's not getting fuel; then suddenly, at constant throttle, the bike will bolt forward, very abruptly, and engine power will come normally for a while..
I've tried several brands of fuel.
The bike's mechanic, whom I believe to be very good, can't find anything out of spec.
Don't know what's wrong, but at times this bike is genuinely un-fun to ride.
How severe is this problem in my opinion? In all other respects, I think the bike is superb; but this behavior has made me regret buying the bike, and I can not recommend it to new purchasers.
