Exhaust servo unit problems?

[Audi403]

Hey guys,

Has anyone else had issues with the servo units on their bikes? Mine is a 2019 with 22,000km. I noticed a couple of months ago that the exhaust flap wasn't working, I assumed it was seized. The valve sticking or seizing up seemed to be a common complaint amongst the Wethead owners. Yesterday, with the silencer off, I turned my ignition on and noticed the valve didn't operate. I tried starting the engine and the valve still didn't move. The weird part is that I have no warning lights on and no faults found when scanning with the GS-911. Next, I connected my GS-911 and ran the exhaust flap test. The Hex software told me that the output actuation completed successfully, but still no movement on the flapper. I removed the cables from the valve going to the servo motor. I tried rotating the flap in the exhaust by hand, and to my surprise, it rotated completely free. I can spin the flap valve all the way closed with very little effort, and when I release it, it snaps back. I turned on the ignition again to see if I'd get any movement from the servo motor with the cables disconnected from the valve, but it still didn't work. Next, I pulled the servo unit from the bike and opened it up. I tried rotating the pulley inside of the servo unit, but it doesn't rotate by hand. Here is a picture of the pulley inside of the servo unit which drives the cables to operate the exhaust flap:

Today, I hooked up the partially disassembled servo unit to the bike, turned on the ignition, and to my surprise, it worked. I then reassembled the servo unit and reinstalled it on the bike. It self-tests successfully on every ignition-on cycle and operates the exhaust valve.

Has anyone else found this intermittent failure? I'm not sure why unplugging it and plugging it back in has fixed my problem, but it has. Now I'm wondering how long it's going to work for before this happens again. They cost about 300USD new from BMW, so if it ever fails, I may just replace it with a servo eliminator. 

[wbw6cos]

The only  issue I had with the flapper vavle was a loud squeak at cycle-on.  While the bike was under warranty, I wanted it on the record at the dealer for a 6,000 mile service.  Of course, when the service advisor went to listen for that noise, it did not happen.     They claimed the tech checked it and did not find any issues.  Within a few days after, the loud squeak started again.  WTH?  

 

Based on some thread chatter about the exhaust flapper valve I bought some AC Delco Rust Penetrant and Inhibitor spray lube.  It worked.  It will last a while, but as a preventative measure I apply it when I change out the rear tire.  That usually calculates to every 5,000 - 6,500 miles.   

 

I spray that lube at the shaft area of the valve top and bottom, even though the noise originates from the bottom portion; I sprayed there first and the squeak was gone.  The lube comes out foamy, so I cycle the valve a few times and let it soak.  By the time I go to re-install the muffler, the foam is gone.

 

I am glad you got yours sorted.  Perhaps the contacts for the electrical connector had enough crud on them and your unplugging and plugging it back in may have fixed that.  (?)

 

Cheers,

[60Aviator]

Do a search on other forums. Known issue and many threads. 

[Audi403]

6 hours ago, 60Aviator said:

Do a search on other forums. Known issue and many threads. 

Care to share one? I've read most of the threads on this issue. The common issue is that the exhaust valve sticks/seizes. I haven't found a single case of someone whose valve wasn't working, the flapper was not seized and operated freely, and the fix was to unplug and plug back in the servo unit. The connector was snapped into place before I disconnected it, and it was working previously.

[Hati]

47 minutes ago, Audi403 said:

I haven't found a single case of someone whose valve wasn't working, the flapper was not seized and operated freely,

 

That is because you are special 

48 minutes ago, Audi403 said:

the fix was to unplug and plug back in the servo unit. The connector was snapped into place before I disconnected it, and it was working previously.

 

That supports my theory I shared on the other forum.  Some corrosion/foreign object in the plug.

[dirtrider]

Afternoon Audi403

 

I have been thinking on this one on & off throughout today since I read it this morning).

 

I didn't answer this morning as I really don't know what you are dealing with. You would think that if it was connector resistance or open circuit issue at the connector, or in the wire harness, then the system would catch that through the servo feedback or a checksum & you would find a stored fault code or codes. 

 

Not being able to turn the pulley by hand is normal for that type of servo.

 

Getting a proper GS-911 test with it not actually moving is also puzzling __?

 

At the moment about all I can think of is an issue inside the servo (& that is not even firm enough to be good guess). 

 

If it happens again then use a mechanics stethoscope, long screwdriver, or very good ears then run another test with the GS-911 while listening to the servo for inside movement noises.  If it sounds like something  is moving inside but the pulley isn't moving then possibly something is stripped inside.  I have seen some servo types that strip inside (especially at one or the other end of travel)  that can start working again after playing with it. They usually work again until the servo ends up in that one stripped place, then it can't pick up the drive again (again not even a real good guess just all I can think of at the moment).   

 

Another thing to look at (try) is while it is testing (with pulley not turning)  try turning the pulley by hand to see it THEN picks the drive up & starts turning the pulley. I think there is a motor worm shaft (long worm gear) plus an additional gear set inside the servo assembly. If there is a stripped (partially missing) tooth on one of  the gears then it could lose drive when the worm or a drive gear hits (stops at) that broken tooth.  But as long as it doesn't stop there then it might be able to drive right past that bad tooth.  Turning the pulley by hand (servo not running) could still feel OK (tight)  as the driven gear would probably still lock OK on the tooth on either side of the broken tooth (again just a guess).

 

  

[60Aviator]

4 hours ago, Audi403 said:

Care to share one? I've read most of the threads on this issue. The common issue is that the exhaust valve sticks/seizes. I haven't found a single case of someone whose valve wasn't working, the flapper was not seized and operated freely, and the fix was to unplug and plug back in the servo unit. The connector was snapped into place before I disconnected it, and it was working previously.

 

Your Google Fu is too weak Grasshopper and you are naive if you think you are first or only after at least 8-10 years of this being on BMW bikes.

Google Search Results "bmw motorcycle exhaust flap"

About 3,140,000 results (0.46 seconds) 

 

Sorry if you are actually Special. 

[Audi403]

2 hours ago, 60Aviator said:

 

Your Google Fu is too weak Grasshopper and you are naive if you think you are first or only after at least 8-10 years of this being on BMW bikes.

Google Search Results "bmw motorcycle exhaust flap"

About 3,140,000 results (0.46 seconds) 

 

Sorry if you are actually Special. 

You do that search and count how many threads you go through until you find someone with these symptoms. 99% of them are due to a seized flapper that they then free up and lubricate. I did my research before posting, my symptoms are uncommon. Sorry you have nothing better to do in your life that you decide to act like a clown on forums that are intended to help people. This thread will definitely help someone in the future who is troubleshooting the same issue. The only downside is, now they have to read through all of your bullshit to find actual help. Have a good one, bud.

[Audi403]

3 hours ago, dirtrider said:

Afternoon Audi403

 

I have been thinking on this one on & off throughout today since I read it this morning).

 

I didn't answer this morning as I really don't know what you are dealing with. You would think that if it was connector resistance or open circuit issue at the connector, or in the wire harness, then the system would catch that through the servo feedback or a checksum & you would find a stored fault code or codes. 

 

Not being able to turn the pulley by hand is normal for that type of servo.

 

Getting a proper GS-911 test with it not actually moving is also puzzling __?

 

At the moment about all I can think of is an issue inside the servo (& that is not even firm enough to be good guess). 

 

If it happens again then use a mechanics stethoscope, long screwdriver, or very good ears then run another test with the GS-911 while listening to the servo for inside movement noises.  If it sounds like something  is moving inside but the pulley isn't moving then possibly something is stripped inside.  I have seen some servo types that strip inside (especially at one or the other end of travel)  that can start working again after playing with it. They usually work again until the servo ends up in that one stripped place, then it can't pick up the drive again (again not even a real good guess just all I can think of at the moment).   

 

Another thing to look at (try) is while it is testing (with pulley not turning)  try turning the pulley by hand to see it THEN picks the drive up & starts turning the pulley. I think there is a motor worm shaft (long worm gear) plus an additional gear set inside the servo assembly. If there is a stripped (partially missing) tooth on one of  the gears then it could lose drive when the worm or a drive gear hits (stops at) that broken tooth.  But as long as it doesn't stop there then it might be able to drive right past that bad tooth.  Turning the pulley by hand (servo not running) could still feel OK (tight)  as the driven gear would probably still lock OK on the tooth on either side of the broken tooth (again just a guess).

 

  

Thank you for your suggestions. I'm going to continue to monitor it and I'll update the thread with any findings.

[60Aviator]

1 hour ago, Audi403 said:

You do that search and count how many threads you go through until you find someone with these symptoms. 99% of them are due to a seized flapper that they then free up and lubricate. I did my research before posting, my symptoms are uncommon. Sorry you have nothing better to do in your life that you decide to act like a clown on forums that are intended to help people. This thread will definitely help someone in the future who is troubleshooting the same issue. The only downside is, now they have to read through all your bullshit to find actual help. Have a good one, bud.

 

Lighten up Francis. 

[chrisolson]

LET'S ALL CONCENTRATE ON THE MECHANICAL ISSUE AND NOT THE PERSONALITIES .... 

[Skywagon]

I have zero experience with this servo, but I have a good bit of experience with similar servos in other applications. DR’s thought on a stripped gear is very possible. Lubing a stripped tooth on a servo causing it to work is also completely plausible. 
 

For what it’s worth, the servos I have experience with weren’t subject to high heat. When they had similar circumstances, we could open them up and access the gear. I’d would say 80% of the time there would be a couple of teeth sheared. If it wasn’t a critical servo, we would remove the gear and rotate it 180. degrees.
Most servos I’ve dealt with seldom travel more than 50% of the gear circumference. When we examined why this happened, it usually turned out to be one of two things. Moisture or water could cause one of the shafts to partially corrode binding the gear. The motor was actually strong enough to power through a stuck gear causing the strip of teeth. The second and less common issue was a run away signal to the servo causing it to continually run or running past it’s programmed limits. 
 

Again I don’t have knowledge of this wet head issue, but if heat can cause condensate or water entering the servo unit, it’s understandable how corrosion could cause the issue and a lube/water displacement fluid might help.

 

Can this servo be opened or is it sealed?  If anyone has replaced the servo perhaps it could be opened and examined.

 

Good luck. If you find the issue post back please. 

[Audi403]

8 hours ago, Skywagon said:

I have zero experience with this servo, but I have a good bit of experience with similar servos in other applications. DR’s thought on a stripped gear is very possible. Lubing a stripped tooth on a servo causing it to work is also completely plausible. 
 

For what it’s worth, the servos I have experience with weren’t subject to high heat. When they had similar circumstances, we could open them up and access the gear. I’d would say 80% of the time there would be a couple of teeth sheared. If it wasn’t a critical servo, we would remove the gear and rotate it 180. degrees.
Most servos I’ve dealt with seldom travel more than 50% of the gear circumference. When we examined why this happened, it usually turned out to be one of two things. Moisture or water could cause one of the shafts to partially corrode binding the gear. The motor was actually strong enough to power through a stuck gear causing the strip of teeth. The second and less common issue was a run away signal to the servo causing it to continually run or running past it’s programmed limits. 
 

Again I don’t have knowledge of this wet head issue, but if heat can cause condensate or water entering the servo unit, it’s understandable how corrosion could cause the issue and a lube/water displacement fluid might help.

 

Can this servo be opened or is it sealed?  If anyone has replaced the servo perhaps it could be opened and examined.

 

Good luck. If you find the issue post back please. 

Thanks for your input. I attempted to open the servo, but it isn’t designed for it. I believe I would have destroyed it. If it does completely fail, I will gladly open it up and post pictures.