K1200S Stranded me; diagnosis suggestions?
’06 K12S, fairly new to me, no issues until yesterday on a drive way out in the TN twisties. Started noticing slight, quick off/on surge in gears 3-5 at about 6-7k rpm. Ride on about 15 miles, and it’s now in all gears and at nearly all rpm and getting worse. Bike dies the first time headed up the side of a mountain on switchbacks. Get it restarted several times and to top of mountain. Figure it might be one of the umpteen heat-related issues with this bike, since it’s the hottest day I’ve had the bike out yet. Wait 15-20 min. Still won’t start for more than a few seconds. Slowly coast 9 miles back down mountain (no servo issues with my bike at least, since I lived through the experience). Stop and start with at least 5 min. wait at least 10 more times, including having to push the bike out of several intersections (decided to go back home through civilization, in case I got in real trouble). Despite the ambient heat, however, water temp never gets any hotter than I've had it up to previously. Finally, battery dies, and that's it.
Possibly relevant info? BMW newer hydraulic cam chain tensioner installed (Abe Lincoln stovepipe hat). BoosterPlug installed (and routed to a suggested location, next to the right air snorkel; I never had the extent of stalling or surging or idling noise or other throttle issues some did, but put it on anyway. To be honest, never noticed any difference, better or worse, since installing it). Hottest and most humid day bike ridden so far, as mentioned above, and problem got worse as day got hotter. Only things done since last ride: top off with no ethanol gas, and throw in a can of the much beloved Liqui-Moly 4T racing fuel additive. In case one of those was the issue, I stopped at a gas station on the way back, and topped off again to dilute any ill effects of either the newer gas or additive, but it just kept getting worse. Dash never showed a code, until the engine actually stopped running, at which time I got the dreaded red triangle (well, thanks, bike; I kinda noticed you quit running!).
The way the engine was behaving, no way an injector was clogged, or spark plug had come loose. It feels like any spark and/or fueling issues were coming from the computer, not anything mechanical.
Am I stuck buying the Hex GS-911 to hope it will solve the mystery (I've seen a couple horror stories where it said all was well when it wasn't, even though the reviews are almost all positive), or anything else I might try or check which would be simple, or something I was too dumb to consider? Thanks in advance for any ideas or expertise, guys/gals.
EDIT: Just went down to the garage and...after Opti-mate back on all night and battery recovery, she started right up at first touch. Only abnormal thing was for less than a second, the cam chain sounded louder than ever before the fluid got in the tensioner (not merely loud, but like rocks-in-the-case loud), but went away a split second later and never returned. I let her run, repeatedly rolled on and off the throttle, held it at 4k for an extended period of time with no fueling glitches, and heated the water up to the same temp as when it just wouldn't go any further yesterday, and of course, everything ran just fine. Wut...the...fudge?
Last edited by Dobervol; Jun 17th, 2018 at 3:16 pm.