Stalling bike on downshifts

[Gsnelly]

Hi all you knowledgable folks, I would like to ask for some help.
Yesterday while riding my 2012 gsa I experienced a panic inducing slide as the bike stalled as I downshifted approaching a corner. I was travelling at about 45 mph and as I changed down I blipped the throttles as I normally do……but the bike just seemed to give a fluffy response and cut out……as I had released the clutch already, the back locked up and very nearly sat me on the floor.
The throttle is definitely giving that wooley type of response now and then……but that was a first.
It’s on good fuel…..I think! And seems to run well when riding along and on tick over……it just doesn’t seem to like that blip on downshifts.
Has anyone got any ideas what could cause this…..and how I might fix it?
Thank you all

 

[Pukmeister]

Could be a failing lambda sensor in the exhaust, or a worn track or wiper arm in the throttle position sensor.

 

[landmarkjohn]

You could try cleaning the TPS sensor with contact cleaner or suchlike. I have had improvement doing this in the past. Couple screws, 10 minute job, worth a try.

 

[Santa-2512]

TPS, classic symptom

You could try cleaning the TPS sensor with contact cleaner or suchlike. I have had improvement doing this in the past. Couple screws, 10 minute job, worth a try.

if the op does a search, i think on here, there is a guide how to do the strip & rebuild

 

[Steptoe]

……it just doesn’t seem to like that blip on downshifts.

Shall I post the obvious answer.,

 

[Santa-2512]

Hi all you knowledgable folks, I would like to ask for some help.
Yesterday while riding my 2012 gsa I experienced a panic inducing slide as the bike stalled as I downshifted approaching a corner. I was travelling at about 45 mph and as I changed down I blipped the throttles as I normally do……but the bike just seemed to give a fluffy response and cut out……as I had released the clutch already, the back locked up and very nearly sat me on the floor.
The throttle is definitely giving that wooley type of response now and then……but that was a first.
It’s on good fuel…..I think! And seems to run well when riding along and on tick over……it just doesn’t seem to like that blip on downshifts.
Has anyone got any ideas what could cause this…..and how I might fix it?
Thank you all

i never blip the throttle on downshift,s tends to induce a cough, especially when cold

When was the last time it was serviced, and were the TB's synced & balanced

 

[Steptoe]

i never blip the throttle on downshift,s tends to induce a cough, especially when cold

When was the last time it was serviced, and were the TB's synced & balanced

How fuel injection works… When you blip the throttle the fuel cuts off as the revs drop back down with the throttle closed, I think it kicks back in when the revs drop back to 1k revs. If blipping the throttle, especially on a big twin cylinder engine, it can cause the engine to stall and fluff, pretty much what is happening to the OP’s bike

 

[Schtum]

How fuel injection works… When you blip the throttle the fuel cuts off as the revs drop back down with the throttle closed, I think it kicks back in when the revs drop back to 1k revs. If blipping the throttle, especially on a big twin cylinder engine, it can cause the engine to stall and fluff, pretty much what is happening to the OP’s bike

On the other hand, having blipped singles, twins, V4's, IL4's, 6's, triples and umpteen boxers over the past 50 years, the only time I've had the same symptoms as Gsnelly is when, as Pukmeister suggested, I had a failed lambda sensor.

Of course, I'm not selecting a lower gear with a completely closed throttle. Blip to the correct engine speed to match the road speed in the lower gear and change down at the same time, only closing the throttle completely when the lower gear and the clutch are both engaged.

 

[Steptoe]

On the other hand, having blipped singles, twins, V4's, IL4's, 6's, triples and umpteen boxers over the past 50 years, .

Blimey who knew they had all those fuel injected bmw motorbike engines 50 years ago. Of course it could well be be a failed lambda sensor, but you can also usually notice the idle stumbling/hiccuping as well,

 

[TIJ650]

My old oilhead did this at the most inopportune times (like leaned over in a roundabout). I never knew about the TPS sensor fix (which makes most sense) - I used to just give the bike a “good hot breakfast” clean out. Seemed to work for me
My bike had the Wunderlich fuelling module and no CAT on Akropovic full system.

 

[TIJ650]

I’m an old school blipper too

 

[Santa-2512]

::.UKGSer Tech.::

Last topic in the Hexhead section

If you need a new one - do a search on ebay it's a Hella item cost about £40

Dont ask about the price of an oe item !!!!

 

[jefformston]

How fuel injection works… When you blip the throttle the fuel cuts off as the revs drop back down with the throttle closed, I think it kicks back in when the revs drop back to 1k revs. If blipping the throttle, especially on a big twin cylinder engine, it can cause the engine to stall and fluff, pretty much what is happening to the OP’s bike

My 2012 R1200GSA did the same, simple answer was don’t blip the throttle on down changes.

 

[Pukmeister]

I had my right Lambda go tits up when touring Scotland in 2005. I blip on downshifts and the failing lambda caused it to stall when I did. A new lambda fixed it. You will probably notice increased fuel consumption and a terrible idle/rough running if a lambda sensor fails.

I had an intermittent fault with a failing TPS which was very difficult to trace with my GS911 but replacing it with the much cheaper Hella part also solved some poor running issues.

If you have access to a GS911 and a manometer/twinmax/harmoniser it could be worth checking valve clearances, changing your spark plugs, resetting adaptive values, resetting the idle stepper motors and balancing throttle bodies.

 

[Gsnelly]

Hi folks,
Huge thanks for all the info. It has not been serviced for a while ( I’ve done all the easy stuff but not throttle sync etc….)
Sounds like lambda and throttle position sensors could be culprits……maybe my riding? But it’s been a workable technique on every other ( inc injected) bike.
I will have a crack at the sensor clean after a search here, but thanks again…..it was a touch unnerving!
Will report back on whatever the fix is in the end

 

[Gsnelly]

i never blip the throttle on downshift,s tends to induce a cough, especially when cold

When was the last time it was serviced, and were the TB's synced & balanced

It’s only on 14k but it’s been a while……I will get those bits done sharpish, thank you

 

[Gsnelly]

On the other hand, having blipped singles, twins, V4's, IL4's, 6's, triples and umpteen boxers over the past 50 years, the only time I've had the same symptoms as Gsnelly is when, as Pukmeister suggested, I had a failed lambda sensor.

Of course, I'm not selecting a lower gear with a completely closed throttle. Blip to the correct engine speed to match the road speed in the lower gear and change down at the same time, only closing the throttle completely when the lower gear and the clutch are both engaged.

Same……matching engine to road speed……never been an issue before

 

[Schtum]

Blimey who knew they had all those fuel injected bmw motorbike engines 50 years ago. Of course it could well be be a failed lambda sensor, but you can also usually notice the idle stumbling/hiccuping as well,

The synecdoche is thine not mine.

 

[MrC99]

synecdoche

Every day's a school day - thanks for that

 

[Steptoe]

The synecdoche is thine not mine.

I think he’s replaced that already and it made no difference