R100GS sputtering at speed

[datchew]

Originally Posted by Scott Davis

I have a 92 model and just rebuilt both my carbs. I am pretty good at setting them up, PM me if you would like some local help!

I think the float level would be my first check, then balance carbs. While in there, blow out all the jets and ports. Can't hurt!!!

:)

Scott

[snobby british accent]Good show old man. [/accent]

[datchew]

Originally Posted by bgoodsoil

It was a genius that came up with that one right? I'm not an engineer and I hate to badmouth somebody's work but whoever designed that is a moron. Whoever left it that way for decades is even dumber.

There are morons in the engineering world. Trust me... I'm one of them sometimes.

[jeveretts]

Did you ever get this problem sorted out? I am having the exact same issue with my r100gs 1992

[durtwurm]

Check your diaphragms as well! Take them out and look for holes next to a bright light.

[Tim McKittrick]

No one has mentioned fuel filters yet- I chased a similar issue for some time with my R100RT and after going through float settings, valve adjustments, timing, coils, petcock filter socks, and tank and carb venting I finally changed the fuel filters. In my case, the old filters appeared fine- they looked new and had no visible buildup of crud in them, yet they were just restrictive enough to starve the bike for fuel under just the right conditions. Pulling a hose off a carb and opening the petcock appeared to produce plenty of flow as well, and if there was more than a half tank of fuel it was fine because of the added fuel pressure from the full tank. Now whenever I hear of someone having a high load stumble I suggest looking at the filters FIRST- they are by far the easiest thing in the system to change, and cheap to boot.

[StephenB]

Originally Posted by Cirbo

Would the PD tank also have red primer (being poly)? This is the second time I've heard that idea.

I am quite sure it isn't coated.

[durtwurm]

Originally Posted by Tim McKittrick

No one has mentioned fuel filters yet- I chased a similar issue for some time with my R100RT and after going through float settings, valve adjustments, timing, coils, petcock filter socks, and tank and carb venting I finally changed the fuel filters. In my case, the old filters appeared fine- they looked new and had no visible buildup of crud in them, yet they were just restrictive enough to starve the bike for fuel under just the right conditions. Pulling a hose off a carb and opening the petcock appeared to produce plenty of flow as well, and if there was more than a half tank of fuel it was fine because of the added fuel pressure from the full tank. Now whenever I hear of someone having a high load stumble I suggest looking at the filters FIRST- they are by far the easiest thing in the system to change, and cheap to boot.

Tim, I am pretty sure my petcock filters are original ('78 RS). And they represent no problem, plus they look "fine'"as you mention. I think I will change them though I have cleaned 'em up. Cannot hurt.

[StephenB]

Originally Posted by Tim McKittrick

No one has mentioned fuel filters yet- I chased a similar issue for some time with my R100RT and after going through float settings, valve adjustments, timing, coils, petcock filter socks, and tank and carb venting I finally changed the fuel filters. In my case, the old filters appeared fine- they looked new and had no visible buildup of crud in them, yet they were just restrictive enough to starve the bike for fuel under just the right conditions. Pulling a hose off a carb and opening the petcock appeared to produce plenty of flow as well, and if there was more than a half tank of fuel it was fine because of the added fuel pressure from the full tank. Now whenever I hear of someone having a high load stumble I suggest looking at the filters FIRST- they are by far the easiest thing in the system to change, and cheap to boot.

Are you talking about the screens inside the tank or the in-line paper filter that can be used?

+1 if you're talking external paperfilters (VW-type): they seem very restrictive and when I am on reserve the pressure of the remaining 4-5l isn't enough to let gas flow through them when you let them run dry.

[Tim McKittrick]

I was referring to the little clear after-market external filters commonly installed between the petcock and carburetor. All of the BMW's I have ever owned have had them but they never came out of the factory with them. I've seen both pleated paper style units (I think that would be the VW sort referred to above) as well as the sintered bronze style. I had the ones that had the bronze element in them, and they appeared fine. I honestly only replaced mine (instead of eliminating them altogether) as it was easier to plug in a new filter than to find a double ended hose barb to rejoin the sections of fuel line, and I'm a lazy, lazy person.

The filter socks in the tank can be reached by unscrewing the petcock and are easily cleaned- these usually catch the majority of the crud.

[durtwurm]

Originally Posted by Tim McKittrick

I was referring to the little clear after-market external filters commonly installed between the petcock and carburetor. All of the BMW's I have ever owned have had them but they never came out of the factory with them. I've seen both pleated paper style units (I think that would be the VW sort referred to above) as well as the sintered bronze style. I had the ones that had the bronze element in them, and they appeared fine. I honestly only replaced mine (instead of eliminating them altogether) as it was easier to plug in a new filter than to find a double ended hose barb to rejoin the sections of fuel line, and I'm a lazy, lazy person.

The filter socks in the tank can be reached by unscrewing the petcock and are easily cleaned- these usually catch the majority of the crud.

The in line filters if used should be changed yearly. The plastic ones are cheap; the metal filters with replaceable innards are more expensive initially. I was wondering. I thought you were referring to the petcock filters and always thought they just need a little periodic cleaning.

[boxerboy81]

Originally Posted by StephenB

Float bowel level is my initial thought ...

Believe me when I write, it's not your bowel! Though this problem is frustrating enough to have that effect. Someone will usually do that typo in such a thread.

My bike has shown similar symptoms in the past. Riding along and a poor stuttering response that improves if slowing down for a while. It tends to repeat itself unpredictably/inconsistently at higher speeds. A diaphragm problem would be more consistent and predictable.

Advice to me at the time was:

• float bowl level...hadn't been touched, looked correct.
• fuel flow problem. Nope, flowed well from the tap, no ext. filter.
• diaphragms..were ok
• hall effect sensor. Never tested.
• ht leads/plugs. Replaced.

Then whilst on a 4K+ ride, and 1600k from home it happened and wouldn't go away. It proceeded to deteriorate.

I holed up in a motel, went thru the usual trouble shooting checks to no avail. I found a local airhead owner (known via another forum) and he generously helped me the next day. We repeated the checks and got no where. A quick call to a BMW mechanic, who offered the same advice as we'd already performed.

Then he said..."have you pulled the main jet and checked it"?



Haven't had a problem since.

Simple things first. Bowl level, the jet, fuel flow, diaphragms, electrics.

[durtwurm]

Originally Posted by boxerboy81

Believe me when I write, it's not your bowel! Though this problem is frustrating enough to have that effect. Someone will usually do that typo in such a thread.

My bike has shown similar symptoms in the past. Riding along and a poor stuttering response that improves if slowing down for a while. It tends to repeat itself unpredictably/inconsistently at higher speeds. A diaphragm problem would be more consistent and predictable.

Advice to me at the time was:

• float bowl level...hadn't been touched, looked correct.
• fuel flow problem. Nope, flowed well from the tap, no ext. filter.
• diaphragms..were ok
• hall effect sensor. Never tested.
• ht leads/plugs. Replaced.

Then whilst on a 4K+ ride, and 1600k from home it happened and wouldn't go away. It proceeded to deteriorate.

I holed up in a motel, went thru the usual trouble shooting checks to no avail. I found a local airhead owner (known via another forum) and he generously helped me the next day. We repeated the checks and got no where. A quick call to a BMW mechanic, who offered the same advice as we'd already performed.

Then he said..."have you pulled the main jet and checked it"?



Haven't had a problem since.

Simple things first. Bowl level, the jet, fuel flow, diaphragms, electrics.

And while you're in there go to your nearest auto parts dealer and replace the o-ring! These are stock items and will be carried at Carquest and NAPA, etc. That black item looks like an old o-ring. Is it?

[H96669]

Originally Posted by boxerboy81

Then he said..."have you pulled the main jet and checked it"?


Haven't had a problem since.

Simple things first. Bowl level, the jet, fuel flow, diaphragms, electrics.

Looks like someone else had "The little piece of crap floating around the bowl.......sometimes impeding the fuel flow until it finally jams up there and blocks the jet".

Very frustrating the first time, but second time around only a 5 minutes repair job.

[Uncle Pollo]

Originally Posted by Tim McKittrick

No one has mentioned fuel filters yet- I chased a similar issue for some time with my R100RT and after going through float settings, valve adjustments, timing, coils, petcock filter socks, and tank and carb venting I finally changed the fuel filters. In my case, the old filters appeared fine- they looked new and had no visible buildup of crud in them, yet they were just restrictive enough to starve the bike for fuel under just the right conditions. Pulling a hose off a carb and opening the petcock appeared to produce plenty of flow as well, and if there was more than a half tank of fuel it was fine because of the added fuel pressure from the full tank. Now whenever I hear of someone having a high load stumble I suggest looking at the filters FIRST- they are by far the easiest thing in the system to change, and cheap to boot.

You just reminded me of putting appart the petcocks and cleaning the screens.

From inexpensive and easy to expensive and hard; that is how troubleshooting is done!

[Bill Harris]

Originally Posted by Cirbo

I changed the float bowl gaskets shortly after getting the bike (6-8 months ago).

Give us a quick maintenance history of the bike, as long as you've owned it.