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dylanewilliams 10-04-2012 07:55 AM

Hesitation on throttle, and then worse
<!--[if gte mso 9]><xml> <w:WordDocument> <w:View>Normal</w:View> <w:Zoom>0</w:Zoom> <w:DoNotOptimizeForBrowser/> </w:WordDocument> </xml><![endif]--> 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.

pcwirepro 10-04-2012 08:37 AM

1/4" lines coming from the tank reversed?
Do you get a Hissing sound when you open the fuel filler?

Blew out the air intake and overflow hoses with compressed air
Any chance the "loud metallic grinding" is unrelated to the hesitation and stalling? What spark plugs did you use and did you gap them to spec? It sounds like you had a slight hesitation BEFORE you did all the work and now you have more or worse symptoms. Is that right? The Big Brass Screws should be out more than 1/4 turn to get the 1200 RPM you're shooting for. Something is off there. What did you use to do the TB sync?

dylanewilliams 10-04-2012 08:57 AM

I am certain I didn't reverse the fuel out and return lines to the tank, one of the lines is marked, and on top of that this morning I pulled off the fuel in line at the right TB and when I turned on the cutoff switch, I had a solid stream of fuel coming out.

There is no hissing sound when I open the fuel filler, I am relatively certain the problem is not just that I have a clogged breather line if that's where you're going. When I blew it out the air flowed freely.

It's possible the metallic grinding is unrelated to the stalling, however it is certainly tied to the bike dying, so that would mean the dying and rough idling are a new, separate problem from the hesitation

I used the bosch plugs that the BMW dealer sold me for the bike, and did not gap them, I installed them as is

That is correct nothing I have done has remedied the problem:cry, it was there before and got worse.

I definitely agree something is wrong with the TB screw being in so far. I used a mercury manometer to sync the TB's, first equalling the levels by adjusting the throttle cables, then adjusting the air screws to get the proper idle while keeping the sync

One thing I am uncertain of is when I removed the fuel pump plate from the tank I forgot to mark the relative orientation. I reinstalled it so that the fuel pump sits forward and horizontal once everything is put back together. I think it's OK because when I fill the tank up the RID reads full gas, although it reads empty at 5 gallons on a 7 gallon tank.

boxermoose 10-04-2012 09:55 AM

Inspect the hall effect sensor wires - if they are cooked you may want to do a preventive repalcement - there are aftermarket plates much cheaper then OEM - although as I understand it if the sensor fails it's pretty much dead right there

There used to be instructions in the HOW

pcwirepro 10-04-2012 12:07 PM

Any other fuel maint?
Have you done any other fuel maintenance? I ran several tanks with SeaFoam and then finally ended up removing the injectors and soaking them overnight in injector cleaner. It definitely made a difference.
You may even consider this or

Jim Moore 10-04-2012 12:39 PM

Three thoughts. First, I had a similar problem on my 97 RT. It turne dout to be a relay that had worked itself loose. After shotgunning about $500 worth of parts it was fixed by pressing my thumb on the relay to reseat it. Expensive lesson.

Second thought. HES. If you haven't replaced it, it's time. You don't have a classic HES failure, but it's close enough.

Third, your O2 sensor. I had a similar problem with my GS. IT was rleated to the O2 sensor. Pull the cat code plug in the fusebos and see if that fixes it. On your bike pulling the CCP disconnects the O2 sensor.

Good luck.

eric2 10-04-2012 01:17 PM

stick coil. you've replaced everything else

pcwirepro 10-04-2012 01:38 PM

Stick Coils on a '96? Na

Originally Posted by eric2 (Post 19747771)
stick coil. you've replaced everything else

Hmmm. Does the '96 have stick coils? I'm liking the loss of spark idea though. Could explain the "burst of compressed air" the OP heard.

def 10-04-2012 02:14 PM


Originally Posted by pcwirepro (Post 19747943)
Hmmm. Does the '96 have stick coils? I'm liking the loss of spark idea though. Could explain the "burst of compressed air" the OP heard.

No sticks on oilheads, thank goodness. However, it might be wise to check coil impedance with a VOM to insure there is adequate voltage to the plugs. Also, check the plug wires. I don;t know if your vintage has carbon wires but, have a look in a dark place at night with the engine at idle. You'll see corona if wires are leaky. Did you replace any in-the-tank fuel lines? Those lines can crack with age and leave your high pressure side with low fuel pressure. The poor driveability is especddially noticeable at higher RPMs when fuel pressure and full flow is needed. Also, next time, don't buy the Bosch plugs. Too costly. Autolite 3923s are preferred by pre dual-spark boxer owners. They're about $2.00 each and allow the gap to be adjusted with the traditional over-the-end ground electrode. Also, the Autolites improve cold starts and have been known to reduce surging somewhat.

def 10-04-2012 02:16 PM


Originally Posted by eric2 (Post 19747771)
stick coil. you've replaced everything else

With all respect for your willingness to help, it is unwise to give advice if you are not familiar with the advice you are giving. Stick coils, or the coil-on-plug design did not appear until the dual spark engine came along.....waaaaay after the OPs bike was built.

def 10-04-2012 02:23 PM

The burst of air you hear and a grinding sound????....I would remove the OHV covers and inspect the cam chain rails. Rotate the engine slowly with the alternator drive pulley nut. You may have damaged there. Next, if the chain rails look OK, I would remove the starter and clean and lube the mechanicals at the nose of the starter.

Mrmerlin 10-05-2012 08:20 AM

After reading this there are probably a few things that need to be done

Since the driveability issues has never been fixed the two parts you have not addressed are the HES,
and the 02 sensor possibly damaged by the rusty pipe fitting episode.

That said the whoosh of air may be a loose spark plug or possibly stripped out threads causing the plug to come loose.

if not that then maybe the intake manifold has a leak and is letting intake air escape possibly in conjunction with the failing HES

I would also give the fuse relay panel a good going through maybe replace a running relay.

The grinding may be incidental to the running and the battery terminals may be loose,
or the wires that go to the starter are loose or dirty,
or a failing ignition push button.

This is what i would do in order
Remove starter and clean and install,
clean battery terminals.
Inspect the spark plugs for correct torque,
and possibly replace them with the autolites
Inspect the intake manifolds for leaks
Install a new airfilter
Replace the O2 sensor,
Replace the HES

dylanewilliams 10-05-2012 01:20 PM

I am working on the bike now, and have checked the following things:

I felt around the fusebox for loose relays, they all felt OK, but I pushed them all in to ensure they are seated. Per Jim Moore, I'd like to pull the Cat Code Plug, but don't know where it is.

The resistance between the pins at the coil is .2 Ohms at the input, and 7.25 K Ohms between the post for the spark plug wires. The HES document linked to below says that second reading should be 13K Ohms, almost double what I have. The resistance of the spark plug wires on both sides is 6.2 K Ohms, although I'm not sure what they're supposed to be or if that gives new information.

The battery looks fine, it's giving 12.87V

The spark plugs are both carbon fouled. I've never had plugs look like that before on this bike.

I Without yet removing the alternator belt and pulley, just the cover, I don't see any obvious problems with the HES wire. I did notice that the side of the new belt showed stitching, as if it may have rubbed against the engine breather line, although now there is clearance and I don't know if the stitching always showed

In terms of replacing the HES and/or HES wires, I found this

Is this a good reference?

Similarly for the O2 sensor, no wire damage is obvious

Thank you all for all the help so far!

dylanewilliams 10-05-2012 02:09 PM

I found out which is the cat code plug, (it's the pink relay on my bike), pulled it and started the bike. Immediately the bike wanted to run at 2-3K rpm, very roughly, and then died. I reinstalled the CCP and got the same result when starting it, high rough rpm then death.

I took off the belt and pulley and think I found the culprit for the screeching, the spring steel tab which holds the HES wire at the rubber boot at the top of the engine case was broken and rattling around with the belt, so that narrows down the symptoms at least.

jalapenopete 10-05-2012 02:56 PM

new bike?
I had a '98 GS that I rode the crap out of. The last couple of years it was fix this, fix that, what now? The last big trip was from my home in GA out to Yellowstone and back last summer. I had a $2K+ bill to get it ready. The bike was good throughout. But, I got back and said "y'know, it's time for a new bike". Bought a lightly used 2010 GS and I'm happy as a clam. The new bikes are stratospherically (not sure that's a word) better. Of course you'll have these guys telling you that an old GS can be fixed on the side of the road by whittling a wrench out of piece of wood and replacing the starter from a '65 VW parked conveniently nearby, shit like that, but I'm not a mechanic.
Maybe you should just get a newer bike. I mean carburetors.... hello 21st century! A newer bike under warranty means BMW will pick you and the bike up, fix it, put you in a hotel, and the hassles are done.

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