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

*** Edit****

Additional information:

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

Just a thought.... could this realistically be caused by the pressure regulator in the fuel filter?

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?

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.

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

Phhhhhhh. grateful that you have found the answer
I did not understand the half of that, and I have never even heard of a GS211 (are they really that good?) but I was beginning to wonder what could cause such an issue; the "old" answer of it's either fuel or electrics doesn't quite cut it with modern bikes, as you have demonstrated in this narrative.
The standard fault finding technique of "change one thing at a time and see what difference it makes" pointed to the new spark plugs, or did it take a while to develop???

And, no I would never have thought that brand new spark plugs would cause stalling symptoms.

__________________
Dave

An over landing friend of mine once pointed out that big trips don't end because motorcycles break down, they stop because someone doesn't want to fix the motorcycle one last time. Those words ring in my ear as I confront nasty issues like this. The problem was that I had recently done so much work on the motorcycle that I was unable to apply logic to work out what was causing my problem. When it comes to electrical issues many of us scratch our heads. The fact was that instead of just cutting out I watched the reeves diminish over a few seconds until the engine stalled. I assumes it was fuel pressure.

I systematically started at the injector and worked backwards isolating each part out of the equation until I had narrowed it down to electronics/sensors. Having read previous forum posts on similar topics I decided that I would start the day by putting the old spark plugs back in since I had easy access to them. If they were causing a problem it fitted into the logic of tracing the problem backwards... and hey presto!

The GS911 is a powerful diagnostic tool which I've had for a few years now. It saves me paying BMW extortionate fees to plug my motorcycle into their own diagnostics. I've even done digs on the hard shoulder after my fuel pump shorted out in Utah. Take a look here:

home — Hex code

It is sold through dealerships in other countries.