Custom Fixes for Surging & Stalling
compiled by Kristian #562 & Adamx#1001
edited by Kristian #562 & cb_abq #1534
Please read the Disclaimer before attempting any work in this FAQ.

Fixes: The Options

This section discusses surging AND stalling. With  regards the latter, the cry "My Bike just Died" might not be the FI System Problem.

S&S is inextricably linked to FI. And the FI is a synergic system with air intake, fuel supply and exhaust systems. Warranty considerations rule here for most GS owners. All these mods are controversial, and the majority view seems to be that the software solution is safer. I always wait till the warranty runs out or I drop my bike and crumple it before I get the hacksaw out.

Stalling Only:

Check the Battery Connections

by various

See the Battery FAQ for more details on Battery Maintenance. On the GS you CAN just remove the Centre panel to check the Battery. See GS Battery - Easy Access.

Check the Clutch Setting - Stalling Fix

by Nelson

Last week I did some electrical modifications on my '00 F650 GS. In the process I had disconnected the battery. When I finished the work and rode, about 5-10 minutes into the ride, the bike would stall, when braking and pulling in the clutch. I then rode for a while in semi-deserted streets to assess the exact conditions for stalling. Well, it seemed to occur only when braking and pulling in the clutch. Not every time, but only under these circumstances.

At home, I checked the FAQ and proceeded to try the stuff in the list by order. First, I reset the FI. This didn't work. It still stalled under the same conditions. Then I checked the chain and sprockets. They seemed fine to me (I've got 10000 miles no it now). Next, I checked the clutch adjustment. Well, I found out that the clutch adjustment at the crank case was 2 millimetres below spec. Hmmm, maybe this is the problem. I adjusted the clutch at both the crankcase and lever to within spec. Then I took the bike for the same shakedown. Whereas before the engine stalled always around the same spot, now it was impossible for me to stall it. I rode for at least half an hour more, doing exactly what I had done before and no stalling.

So, if your bike stalls when you brake and pull in the clutch, it might well be the clutch adjustment. Though, I still don't understand why. Nelson, Sojourner (Toronto).

See the Clutch Adjustment FAQ for details of how to adjust the Clutch.




Check the Cable to the Coil
by Guz

After checking, software, spark plug, chain, inspecting injector, possible water in fuel, clutch adjustment, computer changes and more. My dealer found and solve the surging that I was experiencing on my 2002. Problem started after 6000 km. Problem, Power cable that goes to the electrical coil was bad assembled in factory. Was not plug in correct and a oxide started affecting the machine. My 2002 is smooth as before.! I was almost buying the Fuel Nanny and stuff. I'm glad the problem is solved. I'm wondering if some people had or have the same problem. guz.

Throttle Cable Adjustment/Routing
by SScratch '01 Dakar Nashville

After disconnecting my battery for an inspection the other night I experienced the dreaded hard-to-start/won't-idle/surging/stalling malady. The advice from the dealer was bring it in for diagnostics, the advice from this board was turn key on, crank throttle WFO and back to closed three times, start and ride 30 minutes to reset computer. I chose option two. After 30 minutes, bike was running but still stalling and surging. I noticed when I turned to full lock the rpm's picked up a bit, so I suspected throttle cable adjustment was in order. After adjusting this, the bike purrs as it did before. I would suspect that this may be the reason that some bikes with the same software version as others do not run as well. A simple twist of the throttle cable adjustment at the grip could smooth out your ride, too.

BMW Procedure for testing for S&S F650GS/Dakar Check List
by Adamx #1001

  1. Check for corrosion at battery cable ends and/or loose battery connections.

  2. Check for corrosion at the BMS control unit/control unit cable connection point – both components – This can cause a problem, but WILL NOT register a fault on the MoDiTeC.

  3. Check fuel pressure (3.5 + - 0.2 bar). If fuel pressure does not match specification, replace fuel pressure modulator – P/N 13 53 2 343 565.

  4. MoDiTec – reset adaptation to zero.

  5. Check and correct clutch adjustment at both clutch lever and at housing. See Service Bulletin 13 001 01 (006) dated February 01, 2001.

  6. Check clutch cable for correct routing and a smooth, consistent, predictable movement. Replace and/or re-route cable as necessary – p/n: 32 73 7 661 757.

  7. Change engine oil and filter. Renew with 15W40 or 10W40 weight oil and new filter. See Service Bulletin 13 001 01 (006) dated February 01, 2001.

  8. Check wheel speed sensor for damage. Replace as necessary. Part number – Front sensor: 34 52 2 345 844 Rear sensor: 34 52 2 345 845.

  9. Check battery voltage/BMW control unit condenser. A simultaneous check and comparison of battery voltage is required. i) Connect MoDiTeC in mode to check battery voltage. This reading will take into account battery voltage as read through the BMS control unit. ii) Attached a separate voltmeter to read voltage directly from the battery. Compare the voltage readings of both voltmeters, first with the ignition key off and second with the motorcycle at idle. At maximum, a two (2) volt difference in the readings of the separate voltmeters is allowed in both the “key off” and “idle” tests. If more than a two (2) volt difference is noted, replace the BMS control unit (note production date of both the original and the replacement BMS control units). When replaced, repeat above voltage check and comparison for correct specification.

  10. Insure that after every update of a control unit program, the motorcycle/control unit program combination is allowed to “adapt” to each other. This adaptation process is completed by:

  1. Completing the update of the control unit program with the MoDiTec.

  2. With the new/update program in place, start the motorcycle the first time. Do not apply any more throttle than required to start and idle the engine. DO NOT REV THE THROTTLE. Let the motorcycle stand at idle until the engine has reached operating temperature (until the cooling fan comes on)

  3. Shut off the engine.

  4. The motorcycle is now ready to ride.

The ECU & Surging & Stalling

Customising the EEPROM to allow upload of Old Version of the FI Software
Robert B., Austria
edited by Kristian #562

This FAQ is about my custom method of fixing the S&S problem. I hope this information will also be useful to other F650GS riders with ongoing Surging & Stalling problems.

What are the S/W Versions and Injector Numbers

by Robert B., Austria


Buying or Swapping an Updated BMS Unit
by Robert B., Austria

Q. O.K. That sounds great, but I can't do that. Does anyone else do it. Can they program it for me and send me the Box?
A.  Yes.
OBD-Tuning do it.

I just received an email from OBD-Tuning. You can buy the F650GS EPROM with the 5001 code on it from them, for $199. See below. This is the Old European Code.

From: "OBD-Tuning" To:
Date: Thu, 22 Aug 2002 14:44:46 +0200

Hi Andre!

Yes, we do offer the pre-programmed chip.

The prices are:
Version 5001 USD 199,-

The prices include Austrian taxes. Please add USD 5,- for shipping in
Europe, USD 10,- for Rest of World. Prepayment with crossed cheque.

Kind Regards
G. Baumgartner

Q. BMS C (Motronic) replacement. Does a new spare BMS C unit would already contain the code (software) so that if you install it out on the road somewhere it would work? I'm wondering if I were in a country with no BMW dealer or techs and my BMS C died that I could have a new one shipped to me and I could install it myself without any special tools.

A1. I priced a new BMS here in Australia, A$686 for it. If you wanted a spare, buy it and fit it to your bike and get latest version loaded to it, then take it out and put in your spares kit. The only worry I have with killing a BMS is.....if you are on a trip and your battery goes open circuit, THEN your VR/Alternator could spike the BMS and fry it. Your battery can break an internal bridging strap between cells, which effectively makes it open circuit, the VR will get upset and possibly die too. Not sure if the BMS has internal surge suppression to protect it from excess voltage. You could make an external protection circuit for the BMS if you are paranoid about a failure. Jack F650GS Australia
A2. Most modern vehicle electronics have diodes and resistors that protect them from over voltage. Most 12 volt ECU's will survive 17-18 volts for 1-2 seconds. Hopefully as this happens the fuses blow and the ECU survives. The ECU should also shut down, so the engine will stop and the alternator should not be able to fry the ECU. Jump starting devices and welding are the usual culprit for damaged electronics. I have seen a 24 volt jump starter that was able to produce 50+ volts. The ECU's go at 32 on these systems, the vehicle owner was using an M4 bolt as the fuse. The protection diodes become £700 fuses. Andy Leeds UK #982

Notes on Programming the EEPROM

Injector Swap and ECU Update

Cable Pump Lead Problem

Problem: Today going along at 130 km/h on my '01 Dakar the engine just died, no splutter or anything. Checked everything that I could think of including the suggestions of the 20 or so other bikers that were on the ride as well. Had spark and fuses are ok but it would appear no fuel but full tank. Checked FAQ but couldn't find anything. Bike is now in farm shed 140 km away waiting for road side service to collect it. Any ideas of what went wrong? Dakarau

Had the same problem with my 650GS. It was due to the cable pump lead going open circuit inside the fuel tank. You can check this from the socket under the seat using a digital volt meter. You should see 12 volts coming from the plug, and <10 ohms across the socket (Fuel Pump). I replaced my wiring inside the pump with longer cables. Any auto electrician should be able to this for you if this is the problem. I am at present interstate and do not have the bike with me, but there are two plugs on top of the fuel tank, one is the pump, and the other is the low fuel sensor switch. Iain in Oz.

based on the (BMS) Wiring Diagrams, the Fuel Pump Plug is the one with the Green and Brown Wires. ed.

Vapour Locks

Engine tried dying yesterday. Dear Inmates, I have a 650 Dakar 2000, it's done 29,000 KM's, and no, I haven't had the 20,000 Km service done yet. ( I'm waiting till I hit the US ) This means the original fuel filter is still in. Yesterday after I crossed the Guatemala / Mexico border something screwy started happening. When I throttled off, it was exactly like the kill switch had been flicked, and whenever I slowed down, I had to give it extra gas so as to avoid stalling. After another 200 KM's the problem cleared itself. Does this sound like the filter finally has given up the ghost, or was my injector partially blocked ( if indeed that's possible ) A friendly mechanic in Costa Rica gave a used filter from a bike that had only done 5,000 kms - and I'm thinking I should exchange it. Whaddya reckon - was it the filter, or the injector. It's definitely not the battery, as when it first started dying I had this big stall at idle, and it took a lot of extra throttle and cranking to get going again. As the starter was turning the motor over OK, I can rule out electrics. As for bad fuel, the most recent tank was Shell V-Power, and then Texaco Super. I think I'll just replace the fuel filter and say my prayers. Jaz #1126

Electrical Modification to Circuit by Inserting a Resistor (Details not confirmed)
from Richard #230

Bosch 5893 Lambda Sensor


A friend of mine owns a 2002 Dakar and has had surging problems. After some investigation he installed a 65 ohm (If I recall correctly) resistor in line with the O2 sensor. He says that this resistor makes the FI computer think the fuel mixture is a little lean and it richens the mixture, making the bike run better. He says he is getting mileage in the low 60's and is not experiencing any surging. I wonder if you could just cut in an appropriately sized potentiometer into the line and dial in the mixture that you wanted (within the limits of the system's programming, of course)? This makes logical sense to me, but as you know, electrons and I don't get along too well, so keep that in mind whenever following my advice about anything electrical. The fellow that came up with this idea was an electrical engineer, BTW. We'll see what happens when he takes his bike in for service. Since he has 15 bikes, it could be a while before he hits 6000 miles, though. However, registering fault codes is not one of his big concerns. The bike apparently is running great and getting 62 mpg, so why worry about such things? I believe that he tried pulling the O2 plug, but thought better of that idea when the mileage dropped to 39 mpg.


After some testing:


My F-650GS Dakar had a huge flat spot from 3-4K RPM and it tended to move around in the power band. I first added a 10K ohm resistor in series to the Lambda sensor, it made it run differently, but not really better. I then fiddled with several different values and found one that seemingly made it run pretty well. But then it came up with a high speed misfire.

I removed all the gadgetry and the bike began to run fine again. Hmmm. My guess is that the engine needed to break in. So my unofficial word is to ride it 2500 miles and see how it runs then. My GS cleared up at about 3K miles. I also tried a Fuel Nanny early on, but due to the closed loop system the bike uses it was detected and compensation was made in the computer for the extra fuel being admitted from the use of the pulse stretching Nanny. The Nanny people tell you to pull the Lambda sensor plug, then the "computer" reverts back to a "limp along" mode and kicks up a fault code-but the pulse stretching nanny isn't detected and the bike runs richer.
The good part is the engine runs "better" and the flat spot is eliminated, but the fuel mileage goes down the hole. I also would wonder what damage if any is being done to the Catalytic converter.

Um, with the FI and cat the F-650GS runs very cleanly, it's just hard to accept that the bike runs so badly you think something is wrong with it, I know if I were to tune an engine to run like that the customer would bring it back with unkind words. For the $$$ they get for these things It's rather disheartening at first to take the fact the thing emulates Chitty-Chitty-Bang-Bang.

Take a couple of good road trips with the bike, I found mine got better with use.




Projected Tip Spark Plug Fix

by cb_abq #1534

Problem: The stock spark plug (NGK D8EA in early models, NGK D8EB in later models) can contribute to surging by allowing carbon buildup in the combustion chamber and on the valves.  The stock plug has also been attributed to the "flat spot" at approximately 4000 RPM.

Solution: Replacing the stock plug with a standard projected tip or projected tip Iridium plug, may prevent surging and smooth engine performance.  This is particularly helpful if installed at or before 600 mi.  

Regarding resistor plugs: All Iridium plugs are resistor plugs.  Replacing a non-resistor plug with a resistor plug has no documented effect on reliability or performance.  Non-resistor plugs will eventually be replaced by resistor plugs.

All iridium spark plugs produced are resistor version. The reason for this is almost all future applications will require resistor spark plugs and non-resistor spark plugs will be phased out over time due to less demand. The resistor in the iridium spark plugs won't affect the performance of your application due to the diameter of the center electrode tip. This spark plug requires less voltage to fire. Jon MacQuarrie Technical Customer Service Representative


Stock Plugs Manufacturer Part No.
Standard Projected Tip    
  Denso X24EPR-U9

Iridium Projected Tip

  Denso No direct replacement listed



Surging & Stalling FAQs

Q. If I disconnect the O2 Sensor ALONE, will that fix it.?
A1. No. Robert #1071
A2. It will generate fault codes in the 'Mo' which your dealer will see. If you care. BradG


Q. If I do a REGULAR OCTANE Fuel Map, (Which has been said to give better low-end performance & possible smoothness) but I ONLY use PREMIUM, (cause' that's all you can buy here) will that ruin my engine in the long term. I understand you CAN use the Low Octane (Reg. Fuel) Map with both Premium & Regular.

A1. IMO it doesn't matter if you use Premium or Regular as the current software will ruin the engine so or so. As the ignition starts at 50° before the climax and the mixture is very lean it is a great stress for the engine in a thermic and a mechanic way. The engine is working at it's limit with the current adjustments. I do not mean that this will damage it immediately but it will decrease the life expectancy of the engine. Robert #1071

A2. IF timing is too far advanced, you will hear pre-ignition. IF there were any engine failures due to severe pre-ignition......we would have heard about it by now. If you change to a low octane fuel map and injector can run regular OR will not make any difference at all. It will simply mean that Regular will have less potential for pre-ignition, due to the advance being reduced a little. Jack

A3. Can't speak on Fuel Nanny theory, but general theory on pre-ignition (pinging) and pre-ignition overheating dictates that the danger is from running too low an octane where higher octane is required - thus BMW's special FI map for low octane fuel. You want to do the opposite, running hi octane in a low octane environment, which seems like it should be much less critical. Contrary to popular belief, hi octane fuels tend to run slightly cooler, with marginally less "power" than regular. (Yes, for the purists, this is a complete bastardization of terms, ignoring flame fronts, octane compression ignition limits etc, but the effect is the same.) So I think it would be safe and the bike should perform OK with hi octane running under a low octane map. The opposite is NOT necessarily true. Todd #389

A4. To make the engine running without trouble with low octane fuel you have to do one or more of the following: Improve the combustion chamber design: cylinder head, piston "top", valve cooling, spark plug placement, spark plug type and so on. Lower the compression pressure (not necessarily compression ratio, that depends of filling). Lower the ignition timing. Increase the fuel/ air ratio. Probably forgot many other mods. In the Rotax engine most parameters (as to engine design) is set. The low octane map must be ignition advance and/ or fuel- air ratio. BIG QUESTION : If I can believe my mechanic I have the high-octane map installed. My bike is running a lot better (as to small stumbling and power drops) when I use low octane fuel. When running on high-octane fuel the symptoms are much more pronounced. I have tried several times to switch octane. Three and four petrol tanks filled in a row with one or the other. Haakon #626

A5. Still using the standard map. I have tried all ranges of fuel and I just can't feel the difference but I stick to Premium. BradG

A6. Running premium gas on the regular map should present no problem just wasted expense. Stuportech

A7. Unlikely you will hurt the engine using HIGHER octane than required. A major gasoline company in the United States was taken to court over promoting their hi-octane fuel. I believe the quotation from a public action agency was was..."you won't hurt the engine, but will be wasting $$$". Their new advertising has the disclaimer, "for vehicles that require premium fuels".  There is also a case to be made that engines might benefit from raising their octane as they get older. Carbon build-up in the cylinders artificially increase the compression ratio, and the heated carbon deposits can act as "glow plugs" to prematurely light the fuel/air mixture under compression. Marty #436

Q. If I buy a Fuel Nanny, but don't want to do the Snorkel Mod as I want to keep the Stock Exhaust, I'm not interested in a 1 or 2 BHP Power increase and it rains like a Monster here and I don't want a wet Airfilter, will that Fix it.?
A1. The FN and disconnecting 02 sensor completely fixed mine. The 10.1 map solved the stalling but not the surge. You do not have to do anything else to notice how nicely it runs this way. I have a stock pipe and only a slightly modified snorkel. Instead of chopping it off at the air temp sensor end you can just cut a sharper angle at the existing end. It will about double the opening without exposing the system to rain and tire muck. The mounting pin remains. You'll have to just take a look to see what I mean. I installed a K&N filter so a little water would not hurt in any case.


Q. Does the LATEST Fuel Nanny TFi 1030 have spade connectors or is it also a rip-into-the-wire job.?

A1. Yes. Installs just like the older model. You can take it on an off at will.

Q. Are all you FNer's still using your FN? How many have NOT done the Snorkel Mods AND NOT done any Pipe Mods.? What is YOUR bike like.
Mine runs very well. I'll never go back to stock again. It is worth spending some time tweaking the FN too. All bikes are different but you can start with the factory settings and go from there. The instructions are pretty clear. BradG

A2. It has been my experience that the 10.1 software, set to regular gas, original fuel nanny turned down about 25%, with stock intake and exhaust, make a great running bike. I didn't disconnect the O2 sensor. I use the FN no other mods but fuel map , bike runs nice, stumbles sometimes when cruising a constant speed because of the FN. I have backed it down per their instructions but need to go a hair more. I know the exact problem you are describing. After long phone calls with the folks at FN I agree with their assessment of the problem. BMW is using a car type FI system. A car has enough mass and rolling resistance that engine power is always need to maintain a constant speed. You motorcycle is much lighter. The bike gets into a position where it has not load on the engine monetarily and the computer doesn't know what to do so it shuts off. That is what you are feeling. The Fuel Nanny just give the injector a very small longer of signal and it gets you through this very small time period. And it works. I am a believer. I can unplug the FN and the problem comes right back. I do lose a few MPG in the process. I agree the stumble is maddening and bugged the S##T out of me. Stuportech

Surging Poll
Poll # 1:

to Jun '01


Note the DATE of this Poll. BMW would appear to have fixed MOST (but not fine-tuned) of the Problems, with the updated S/W by now. The Poll also includes comments from those having done the injector swap.

For GS owners, please indicate build date, country, modifications to injector and/or mapping, and whether your bike stalls and/or surges. Maybe we can gather our own statistics.

'02 Surge Poll:
Jul '02

'03 Surge Poll:
to May '03

Fuel Filter Fixes Surging Feedback

Some of these may be in the Feedback above, but it's important enough to isolate these out: See the Fuel Pressure FAQ