2006 BMW F650GS Dakar stalling every 15 seconds

[Brainrotting]

My poor motorcycle has developed a strange symtom, it cuts out as regular as clockwork after 15 seconds. The revs start to drop at 12 seconds forcing the engine to stall at 15 seconds.

My friend was riding the bike when it started to stall and he reported that the stalling started happening intermittently although it now occurs consistently every 15 seconds.

Now, this bike has quite a history. I've ridden it around North & South America; it has 80,000 miles on the clock and was recently rear ended. In the process or repairing the motorcycle I had to replace the rear subframe and this symptom has reared it's ugly head directly afterward this.

I have a GS911 so I plugged it in, but the fool that I am I reset the fault codes to see if a new fault would emerge, but not before I noted that it had previously reported issues with the injector that were no longer there. I've been unable to get the fault codes to reoccur despite the motorcycle continuing to cut out. Using my GS911 the only fault I've diagnosed so far is a faulty radiator fan. Although that is probably a separate issue. Injector, fuel pump, tank venting valve, idle actuator and temperature warning light tests show that these are working fine.

I have reset the BMS unit and checked connections to the fuel pump.

The battery is reasonably new, the spark plugs are brand new.

Recent work includes:

• New rear subframe installed (involves lots of unplugging of sensors including ABS)
• Throttle cable replaced (involves opening ignition housing on right hand grip)
• Valve shim adjustment

I have had previous electrical issues with a shorting cable coming from a relay to the fuel pump, and a shorting to the air intake sensor in the air snorkel. Both have repairs to the cables, a visual inspection shows they look fine. My side kick sensor has been removed, a visual check of the wiring there also shows all is OK.

I am looking through the wiring loom for issues.

Have any of you had a similar problem, or can any of you point me in the right direction? I'm thinking it's electrical, a sensor or something but would love to have some wise words from any of you who may have suffered similar symptoms.

Many thanks

 

[Brainrotting]

I just wanted to add to my post that now the temperature outside has dropped I timed how long it took to stall and in the cold it takes longer; 24 seconds

 

[Dansin]

Faulty regulator? Are the battery terminals clean and tight?

 

[oblertone]

Run it ...

... with the petrol cap off and see if it stalls because you may have trapped the fuel tank breather pipe when you rebuilt it

 

[Brainrotting]

Hi guys,

I'm going to try both of the things you've suggested in that morning (I'm in California right now with the clock ticking to get the bike shipped to the UK before I arrive at Christmas). I've been reading through forums and interpretting others symptoms in relation to mine I'm thinking my problem is most likely fuel pressure.

I have recently noticed a problem of petrol leaking into the top of the fuel pump area and I've been unable to locate where it's coming from. I guess it could be related to this issue if there is excess pressure in the system. My current fuel filter and fuel pump were replaced at the same time and they have 20,000 miles on them. I would expect more milage from my fuel pump but I could have replaced the fuel filter by now and I'm wondering if the regulator in the filter could be causing me problems.

I've done so much work on the motorcycle recently it's hard for me to apply logic as to where to look but this looks like a good place.

My battery is sealed and is new (6,000 miles) so I'm pretty certain I've got good voltage going on.

Thanks for your help and I'll update you with my progress

 

[rc mad]

have you tried turning the ignition on then twisting the throttle full open and closed three times? It sounds like you've had the throttle partially open when starting the bike and it's misreading the throttle position. It's worth a shot as it sounds exactly like what happens if the throttle is open at startup!

 

[Renatus]

My mate's Dakar suffered from erratic behaviour and stalling which took him and a couple of garages months to find, and I believe in the end it was either the lamda sensor or the air temperature intake sensor. I'll probably speak to him on Sunday so I'll check.

 

[Brainrotting]

I can now rule out:

Injector, fuel filter, fuel pump.

I ran the fuel line direct to the injector by-passing the filter. No improvement
I've started the bike with the fuel cap open to rule out a blockage in the breather. No improvement
I by-passed the fuel pump control by powering the fuel pump directly from the battery and that DID work. This rules out the fuel pump and injectors.

I disconnected what I think are the Throttle Valve Switch and Idle Control Device which are the two sensors on the main throttle body. Again the bike DID work.

I've been visually inspecting the wiring loom and can't see any problems there.

Is there a way to test if a sensor is working or not without purchasing a replacement? Is there a relay I should also be checking?

Many thanks for your suggestions so far. Oh, and I have done the throttle reset by opening the throttle wide three times and waiting 20 seconds. I have just replaced the throttle cable so it was possible there was an issue here.

Just in case it is relevant. Using my GS911 I tested the radiator fan and noticed it no longer worked. When I applied a direct current to it from the battery it switched on fine. I'm retesting this as a different problem but since it's electrical it could be related.

 

[Brainrotting]

The solution

OK: The solution? Spark plugs!

I had systematically worked back through the fuel system until I isolated the electronics as a problem. Disconnecting the two sensors on the throttle body made the motorcycle run again, connecting them and the stalling came back. I thought it was coincidental that two sensors would stop working at the same time but before I got the voltmeter out to check the visually good wiring loom back to the ECU I wanted to rule out the spark plugs I'd recently replaced. I put the old ones back in (which I always keep just in case) and bingo!

So the NGK Iridium DR8EIX spark plug is the culprit. The old stock D8EA's work just fine.

Now I've just got to make good all the work... exposed wiring loom and bike in bits. I'm just grateful the problem is a $15 part and not a $400 part

I can now get my motorcycle to the docks in time to ship it back to the UK

 

[rc mad]

Cool, at least you got it sorted

What was the intention of the different spark plugs tho? I've always fitted the standard ones every 6k, I keep the old ones as spares too

 

[Brainrotting]

To be honest I hadn't paid to much attention to the spark plugs. I just wanted to replace the stock ones that I'd laid my hands on in a remote part of Guatemala. Figuring that they weren't the normal Iridium plugs I usually put in I replaced them when I arrived in the U.S.

From what I recall I believe I have had extended tip Iridium plugs in this bike before so it's strange that these should cause an issue, but they clearly did.

I included the model of spark plug in the post just in case someone else runs into a similar issue. On this occasion the stock plugs work a treat.