Theory On Our "Stalling/Stumbling" Issue

[MotocycleWriter]

I took my Terra from the heat of Alabama (where it runs great) to the mountains of Colorado last week. I was thrilled with the performance of the big thumper. It totally outperformed the DR650s in every category, including being the ONLY bike that didn't have a problem other than an almost new CRF250L. At any rate, it did have a hiccup, though.

One morning it was pretty cool. I've always suspected this battery is weak as it just doesn't turn over the motor that hard. Good thing it starts easy. So, I fired it up in the morning when it was about 45 degrees. It BARELY started because the battery was weak. It is the original battery and just seems... weak. Anyway, I got it out on a mountain road that it had been killing all week and stumble, stumble, stumble... Even after the engine warmed up and was at speed. It wasn't until a little later in the day when it really did warm up that it started running right and stopped stumbling.

When a weak battery is cold it is even weaker since the chemical processes that drive it are slower. A weak battery means low voltage, especially when under a load. Is it possible that part of the stumbling problem arises as a result of low voltage across the bus? Apparently some bikes run great and others run like crap. Could this bike come with a finicky voltage regulator so that bikes that stumble aren't getting a nice steady voltage? Or a bad reference voltage? Driving all the electronics on this bike takes some power and opening and closing solenoids (like a fuel injector) can play havoc with the voltage on the power bus if the voltage regulator isn't doing it's job. We have this problem with satellites opening and closing valves for thrusters and if you don't get it right, you're going to have major control problems. This could be absolutely nothing or a contribution to a troubling issue.

Comments?

 

[Trail Boss]

I haven't ridden my Terra in cold weather so I can't comment on that being a contributing factor. However, I do ride my Terra in warm and hot weather (I'm located in central Texas) and my bike has stalled in both warm and hot weather.

 

[Tinken]

Could this bike come with a finicky voltage regulator so that bikes that stumble aren't getting a nice steady voltage?

Yes, I read somewhere about someone having a similar issue on the TR650, where the lower voltage caused efi issues.

 

[WayneC]

The alternator stator and the VR is the same as on the 650GS and F800 series BMs, the original version of it regulated to 13.8-14.2v and it was undercharging batteries, you can look over at Advrider for discussion on it including the input from an ex BMW service manager, the later versions of the VR were upgraded to regulate at 14.4 volts which is needed for AGM/Lithium batteries. There have been no problems with reliability of the VR though

What I found surprising in GS911 testing though was that the VR on the Terra was regulating to the lower voltage when I expected the VRs would be the later version

 

[Scud]

Not having a TR, I don't have direct experience. However, what you've described is a known issue on some Moto Guzzis. Remedies include keeping the battery fresh and fully charged, supplemental grounding of the voltage regulator, and installing a MAXI fuse for the charging circuit.

 

[James Rideout]

Being from the east coast of Canada my Terra is used to big outside temp fluctuations.......I've scraped frost off my speedo so I could see how fast I was going and that afternoon be 25c......my Terra runs way better in cold temperatures (below 20 deg c) it never stalls or even stumbles ....in the summer I run the eruption mod and the bike runs just like it would in fall or spring...summer here in my part of Nova Scotia can reach 40 deg with humidity .....I'm not even going to attempt to.convert that to F....+30 deg outside and my rpm fluctuate big time idling, stalls constantly and my temp gauge is usually 3/4....the eruption helps alot in high temp.....a few months the later I reinstall my factory sensor and it's runs pretty well.....because I swap them every 3 months I don't think my ecu really adapts to it like comments in other threads............long story short I don't think a battery is the problem.... The factory map is just way to lean.....not to say in your case u never had a weak battery or faulty Vr.

 

[WayneC]

The engine sensors and actuators etc are all as per the 650GS/X BM models so the answers on any instabilities lie over in threads on those models at Advrider and elsewhere. The G650X guys at Advrider have really done some good work on identifying instabilities in 02 and Idle Actuator

The 02 sensor in particular has been identified as a problem as it is run from 12v rather than 5v as most vehicles do

With the Terra though without knowing the BMS-E firmware version in specific machines it is not possible to compare results and behaviour between machines, there are very significant diffeences between the early firmware and the final version.

 

[johnsweet]

Being from the east coast of Canada my Terra is used to big outside temp fluctuations.......I've scraped frost off my speedo so I could see how fast I was going and that afternoon be 25c......my Terra runs way better in cold temperatures (below 20 deg c) it never stalls or even stumbles ....in the summer I run the eruption mod and the bike runs just like it would in fall or spring...summer here in my part of Nova Scotia can reach 40 deg with humidity .....I'm not even going to attempt to.convert that to F....+30 deg outside and my rpm fluctuate big time idling, stalls constantly and my temp gauge is usually 3/4....the eruption helps alot in high temp.....a few months the later I reinstall my factory sensor and it's runs pretty well.....because I swap them every 3 months I don't think my ecu really adapts to it like comments in other threads............long story short I don't think a battery is the problem.... The factory map is just way to lean.....not to say in your case u never had a weak battery or faulty Vr.

My temp fluctuations are big too, being in northeast part of Maine, spring and fall riding temp 23F, -5C up to 50F, 10C and summertime anywhere from 60F, 16C up to 85F, 30C degrees. never stalls in cool weather only when warmer temps prevail, I have always started the motor and then put helmet on, coat on, gloves on, by this time a good 5 minutes the motor is warm, this has almost eliminated any stalling issues for me.

 

[MotocycleWriter]

Temperature wasn't the issue I was describing. I was hypothesizing that voltage played a role. In this particular case the lower temperature seemed to weaken the battery, a fairly common phenomenon with batteries. So, the battery voltage was temperature dependent, not the EFI.

 

[Mark_H]

Ok here is proof that voltage has nothing to do with the stumble factor.
A 2014 Strada with 3350 km on the clock and a very good fully charged battery, possibly the worst case of a stumbling bike I have ever seen.
This is right after an ECU Reset, warmed up to normal temperature with fan in/out twice, but nothing seems to make any difference to this bike.
Hot or Cold, 3 min warm up or not, fitted with Wuka or not, Dyna-Boost on or off, whatever I do this bike is a full time stumbler.
Riding it is a nightmare, it is on normal 16/47 gearing so in traffic the clutch has to be slipped to keep it above 2500 rpm or it dies constantly.

Cheers, MH

 

[wferrari]

Don't discount the humidity factor. The more humid is the environment, the more the engine suffers.

 

[kiwiape]

Ok here is proof that voltage has nothing to do with the stumble factor.
A 2014 Strada with 3350 km on the clock and a very good fully charged battery, possibly the worst case of a stumbling bike I have ever seen.
This is right after an ECU Reset, warmed up to normal temperature with fan in/out twice, but nothing seems to make any difference to this bike.
Hot or Cold, 3 min warm up or not, fitted with Wuka or not, Dyna-Boost on or off, whatever I do this bike is a full time stumbler.
Riding it is a nightmare, it is on normal 16/47 gearing so in traffic the clutch has to be slipped to keep it above 2500 rpm or it dies constantly.

Cheers, MH

man you got it bad, mine use to be difficult to hold at 1900 rpm. Does it splutter when cold? Does it miss with roll on / off throttle? Have you got Pulstar plugs to put in it? Has it ever been on the MOSS or OSS tool? If you cant get to a OSS Tool, do the Pulstar plugs and bigger injector, then I will help you rest adaptive learning etc.

 

[Mark_H]

man you got it bad, mine use to be difficult to hold at 1900 rpm. Does it splutter when cold? Does it miss with roll on / off throttle? Have you got Pulstar plugs to put in it? Has it ever been on the MOSS or OSS tool? If you cant get to a OSS Tool, do the Pulstar plugs and bigger injector, then I will help you rest adaptive learning etc.

Actually its not my bike, I am helping a friend sort it out as best we can.

In answer to your questions, it splutters and farts like this whatever the engine temperature, cold, hot or warm.
It misses between 1700 and 2300 rpm going up and backfires on the overrun, but otherwise runs well.
It now has new Brisk AOR10LGS Plugs and they made no difference whatsoever.
It is running on Blaze 100 RON fuel (No Ethanol)
The bike has never been MOSS'd from new, its only got 3350 km on it. We have no access to MOSS, OSS or anything else here.
If I fit the Wuka back on it, nothing much changes, it runs a little better but still has the 1700-2300 flat spot.
If I switch on the Dyna-Boost unit that also makes it run very well, seems to have more power and smoother, but it still has the 1700-2300 flat spot and will still stall.

It is the worst I ever saw or heard of, not so much as a random stall but an almost constant one. I can actually make it stall just by trying to hold it at 2000-2200 rpm.

What disturbs me is it is a 2014 bike sold to the owner in Jan 2015 and should have the latest OEM Map, probably a lot more up to date than my early 2013 model (No MOSS)

 

[hasenpfeffer]

Ok here is proof that voltage has nothing to do with the stumble factor.

This only means voltage isn't a factor on that particular bike and situation. Don't discount voltage as a possible factor on a different bike or in a different situation.

As for the stumble monster,

Head gasket problem? Is there a coolant leak?
Is the O2 sensor bad?
Are any of the sensors bad?
Is the crank position sensor not working correctly?
Are the valve clearances in spec?

See if you can send the electronics to the California headquarters for updating. Beyond just a reflash, early on in TR history there was a rumor that some ECUs had corrupted adaptives and needed a MOSS reset to fix.

 

[WayneC]

Or even incorrect firmware loaded, it is not unknown in the industry, errors do occur.

Ensuring the firmware is either 8543015 (ECE) or 8543016 (US) is important

 

[mag00]

That sounds like the tps fighting with the stepper motor and ecu. I would call that surging, not stumbling. .

I'm not remembering if you have done the pod mod?

Will it idle without throttle input? (Standing away from bike)

 

[hasenpfeffer]

That reminds me, also check the idle air mechanism for cleanliness.

 

[dmw_az]

Wow, that is really bad. My bike has never idled like that. It would stumble when you attempt to take off in first gear when the engine was cold, but it has always idled fine.

 

[Mark_H]

Gents, thanks for all the replies, some of you may have misinterpreted the video. The bike idles perfectly at around 1550, this was not the bike idling it was me slowly opening the throttle to get it to hang around 2200 rpm which is where it stumbles. If I open the throttle quickly and rev it through this phase it runs well and similarly when riding it, there are no problems until I try to or have to use this particular rev range at any time.

@ Hasenpfeffer - The answer to all of these questions is no, the bike has only covered 3350 km and runs perfectly well under power and acceleration, it just stumbles around 1700-2200 rpm, nothing else. I have no intention of sending the ECU to California, the bike is in Cebu Philippines.

@WayneC - How does one find out the firmware issue number with no access to MOSS or GPR ??

@mag00 - The bike was not at idle, it was me opening the throttle very gently, it was not surging. I do not believe the TPS is fighting with the Stepper Motor. As for POD MOD, no I have not and will not do one until I find it really necessary. The bike idles perfectly with no throttle input required.

This bike is a new 2014 model, it does not have any issues with the way it runs when on the open road, all it has is this stumble or flat spot between 1700 and 2300 rpm which makes it a a PITA to ride in slow traffic. I was demonstrating the stumble by making the bike run at 2200 rpm and showing exactly how rough it can get. I can make the bike stall just by keeping it at 2200 rpm and it will fluff and fart and eventually misfire so much as to stall.
This is the issue and I do not believe it is the Throttle Body Fuel wetting or general lean running.

To a certain extent I can make my own Strada do exactly the same, but not as bad as this one.
Gents, this is the Stumble as recorded. I believe it is a fault in the ECU map which at small throttle openings does not give the engine adequate fuel.

Cheers, MH

 

[WayneC]

Mark, the Terra I rode here with the latest firmware does not exhibit the problem and I tried, within reason since it was not my machine, you can get hold of me if you like via my web site or get hold of KiwiApe, he knows how to contact me