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Old 10-04-2012, 07:55 AM   #1
dylanewilliams OP
Joined: Oct 2012
Location: San Diego CA and Richmond CA
Oddometer: 15
Hesitation on throttle, and then worse

My bike is having problems. I read through these and other forums, have tried a number of things to remedy my issue, but it just got much worse and I need to figure this issue out now. I ride this bike every single day, I need it to commute on the weekdays and keep me sane on the weekends.

The bike is a 96 BMW R1100GS. I have ridden this bike hard 2 up fully loaded on dirt roads through Central America, the bike has taken a lot of abuse, and I have made quite a few repairs. It has about 70K miles on it. One peculiarity, it has one single throttle cable even though I understand all 96 and newer bikes had the 3 throttle cables.

The problem began as a slight hesitation while in a high gear at a high speed. The motor would hesitate just a bit, as if there had not been supplied enough fuel. I had other work I needed to do, so I did the following:

Replaced alternator belt (I think I still had the original belt on the bike)
Replaced oil pressure switch (It was leaking oil)
Repaired muffler, which was rusted on and required lots of force to remove, which may have translated into the engine block (when I installed the Jesse Bags, a replacement mounting bolt broke the carbon fiber skin of my D&D muffler, which I repaired for a second time after the initial repair finally fell out)
Changed tranny fluid
Replaced spark plugs
Adjusted valve clearance
Synched throttle bodies-air screw had to be adjusted almost all the way closed, w/in turn to get the idle to 1200

I went on a long ride that weekend, and experienced the hesitation more and more, at one point cutting off for about a full second or two. I thought it must be a fuel issue, so Id start with the routine maintenance stuff:

Replaced fuel filter
Completely drained and cleaned tank
Blew out the air intake and overflow hoses with compressed air

I rode the bike about 100 miles that weekend. On the first 25 nothing went wrong, at both street and highway speeds, but after that the occasional hesitation returned. After one left hand turn the hesitation was enormous, the motor almost died. The next day I did the following, figuring (hoping) it was either the TPS or my fuel pump was dying:
Adjusted TPS to .015V at closed (lowest reading possible was .011V) before adjusting throttle body throttle stop screw
Adjusted TPS to .385V after adjusting throttle body throttle stop screw
Synched throttle bodies

I have driven it maybe 100-150 miles since then with no problem until tonight. I just drove home, when I started the bike the motor was cold and took a few cranks to get started, more than normal. Upon starting, it idled fine, but I noticed an occasional very light hesitation on the freeway, just as before. Upon coming to the first stoplight at the exit, the motor died and would not restart. As I tried to restart the motor, I heard a sound like burst of compressed air I hear when turning the engine with a spark plug out, but loud. I also heard a loud metallic grinding for a brief period. As I cranked, the battery charging light flickered, which it has never done before. Eventually I got the motor to start and it ran fine as long as I kept the throttle open (RPM>2000), which I did the rest of the way home.

Upon returning home, the motor died at idle, and when I tried to restart it I heard a loud metallic grinding sound again on the first crank. The second attempt started it but it now idles rough at about 700 or 800 RPM, which it continues to do if I turn it off and on again.

Any ideas help! My ideas were :
A clogged breather line
Clogged fuel filter
Out of sync throttle bodies
Out of position TPS
Bad fuel pump
Unfortunately, I think there is something I am missing

The two threads I initially found to be most helpful were here, but I dont know if they apply since the troubles last night.
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