TROUBLESHOOT: 2011 BMW F800GS engine cuts out

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troy
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TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by troy »

In the middle of BFE along the UTBDR, my F800GS started cutting out intermittently. I quickly surmised it was the kickstand switch. One reason this came to mind so quickly is that the guy riding the F800GS in the UTBDR teaser movie had his kickstand switch do the same thing!

I removed the kickstand switch. Problem solved. OMG! :-o Troy, don't you realize the risk of your kickstand switch being down with the transmission engaged?!!! How can you be so careless with your life and of everyone around you?!!! Yes. Yes I do.

So about a year later, on my last big bike 3 day adventure, my F800GS developed a mystery issue where it would just start dying while I'm riding--just cut out and die. Sometimes it would fire back up before I rolled to a stop. Other times it would strand me for 5 minutes before it would start again. Not the kickstand switch this time. This is different.

I started to notice these patterns:
  • I can start the day riding and ride for hours before the problem starts
  • Once the problem starts, it continues to happen often--as in every 1/2 mile to 3 miles or so
  • The problem goes away after I stop to fill the tank (AHA!)
A few other little things I noticed suggested to me the issue was fuel-related--that the engine was getting fuel-starved.

On my way home and before my final gas stop of the 3 day trip, I had formulated a theory that my gas tank is not breathing. It is my understanding that gas tanks have to be able to pull in air to displace the fuel being sucked out of the tank. Otherwise, a vacuum is created. A strong enough vacuum would compete with the fuel pump's power to suck fuel out of the tank. The more fuel that is pulled out of the tank, the greater the vacuum, and thus, more likely the bike will be starved of fuel.

When I did get to the gas station--after being forced into a huge ditch to get my now coasting motorcycle out of the way of 65MPH traffic, I noticed that when I opened the gas cap, there was a significant whoosh of air rushing into the tank. Theory confirmed? Me thinks so.

I did not have enough miles left to test the theory further, but if my theory is correct, I should be able to put the issue off for many miles by simply stopping to open the gas cap to eliminate the vacuum.....or even ride with the gas cap popped open. Yes, I understand I do not want dirt to get into the gas tank.

You might say this problem really sucks. Get it?! It's a vacuum reference. You know, because of the suction caused by the vacuum? Never mind.

On older vehicles, I've seen this vacuum problem fixed by simply buying a new gas cap--as the breathing hole is in the cap, which has become clogged. On my F8, the gas cap is a more permanent structure than a simple twist-off cap, and it is keyed to the bike's ignition key.

One of these days, I'll not be too lazy to actually look into a resolution. Hopefully I do that before my next big bike adventure...which may be in TX or Canada. Haven't figured that one out yet. :bored:
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Re: TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by troy »

Some more searching suggests my theory may be correct, but others suggests one of the many sensors can be the culprit. This thread looks to be about the exact issue I'm having. This post in particular provides what seems to be good intel on how the fuel system works on this machine:

http://f800riders.org/forum/showthread. ... post302218

Another guy says the "fuel pressure sensor" is affected by fuel temperature, so as you ride and the bike heats up, the gas can warm up, and that can affect things...so bad sensor perhaps.

Another guy suggested all kinds of crap replaced without fixing problem until new fuel pump installed.

Simply popping the gas cap open next time this happens would prove my theory true or false.
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Re: TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by ajayhawkfan »

I hope you fix that before we go to Texas in March.
Rock Chalk Jayhawk, KU!!!

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Re: TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by Hank Moody »

2005 KTM 450 EXC
2009 BMW F800 GS

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troy
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Re: TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by troy »

Hank Moody wrote:It could be your little ball.....
http://advrider.com/index.php?threads/f ... t-34074445
I'm not sure this is applicable to an F800GS. Seems they are talking about those breather hoses on dirt bike gas caps, but I dunno. Point taken, though--anything in the gas path is a suspect to be interrogated.
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Re: TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by Hank Moody »

I thought it was applicable since it came from the F800 forum on ADV Rider. It sounds like to me you are getting a vapor lock due to a faulty ball valve. Read post #4 , #7 and #8. Remember free advise is worth what you pay for it :D
2005 KTM 450 EXC
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Re: TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by safiri »

The whoosh when the cap is opened leads me to believe a clogged vent is your issue (leading to vacuum in the tank).

Looking at the parts fiche (https://www.bobsbmw.com/store/microfich ... GroupID=16) I see 3 possible places this could be caused. (I don't have any experience with a F800, so speaking generalities.)

In order of what I would check:
1. Under the fuel tank, parts 3, 4, 5, etc. Disconnect when bike has stalled and see if vacuum is relieved.
2. Charcoal canister, item 4. Disconnect and see if that relieves the vacuum. Not sure how easy this is to get to when riding. Charcoal is supposed to absorb fuel vapors and then suction / vacuum pulls them in to be burned up. Not sure where the charcoal can connects.
3. IF (big if) the cap is vented (one way, let air in), that could be plugged.

Not sure if you included / saw this link:
http://f800riders.org/forum/showthread. ... r-gas-tank
Safiri Mike
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Re: TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by troy »

Thanks, Mike! That F800riders thread seems to be talking about the same thing the ADV thread Daryl referenced talks about, but with more detail.

I need to take some patient time and remove a few parts to get a solid understanding of how the fuel system on this bike works so I at least know the suspects.

Thanks for the help, guys!

On a side note, the ad system F800riders has on the site is ANNOYING. Way too many ads, and those ads in-line with people's posts is deceptive. Worse perhaps are all the automatic hyperlinks that try to take key terms and link to amazon affiliate links. So I click a link thinking my buddy is sending me to a helpful reference and instead land on some amazon product page that has nothing to do with the subject. Useless and disgusting
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Re: TROUBLESHOOT: 2011 BMW F800GS engine cuts out

Post by xr-nut »

troy wrote:Thanks, Mike! That F800riders thread seems to be talking about the same thing the ADV thread Daryl referenced talks about, but with more detail.

I need to take some patient time and remove a few parts to get a solid understanding of how the fuel system on this bike works so I at least know the suspects.

Thanks for the help, guys!

On a side note, the ad system F800riders has on the site is ANNOYING. Way too many ads, and those ads in-line with people's posts is deceptive. Worse perhaps are all the automatic hyperlinks that try to take key terms and link to amazon affiliate links. So I click a link thinking my buddy is sending me to a helpful reference and instead land on some amazon product page that has nothing to do with the subject. Useless and disgusting
Troy, did you get your motorccccccccikle fixed? And on the second topic, annoying ads, I'm sure you're aware of adblocker plus? It makes a lot of forums bearable. I am noticing more and more that sites are now blocking users of adblock services. Kelly blue book for instance.

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