Fuel Starvation - Tank Vacuum - Honda CRF1000L Africa Twin Forum
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post #1 of 22 (permalink) Old 05-09-2019, 04:05 PM Thread Starter
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Fuel Starvation - Tank Vacuum

I just experienced something for the first time on my ATAS that if I had not had experience with similar symptoms I might be a bit more worried than I am, but at present I am just annoyed. I was just running down the freeway at about 70 mph and went to pass and had a bit of a power lag (on tour setting). Then a bit later when on a secondary road it was starving for power and surging like it was not getting an adequate fuel supply. I pulled over and switched to User mode (set at 1,1,1) and took off. Still the problem, and it was RPM not speed related, like it had a governor. I pulled over again and opened and closed the gas cap, and it began running perfectly again. Has anyone experienced a blockage of the fuel tank venting system, and if so, where is the first place I should look? Thank for the help.

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post #2 of 22 (permalink) Old 05-09-2019, 04:07 PM
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Did it feel like flat spots and surges when giving it the beans? I've had that and am curious as well because I've never felt it on a bike before.

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post #3 of 22 (permalink) Old 05-09-2019, 04:12 PM Thread Starter
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Tequila: Yes, very much so, and I am fairly confident that it is the fuel tank venting due to how I (temporarily?) resolved it. Makes me a bit nervous with a 5,000 mile trip scheduled in 3 weeks.

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post #4 of 22 (permalink) Old 05-09-2019, 09:16 PM Thread Starter
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I typed the above at my office. I left to head home about 15 miles, and I am fortunate that the Honda shop was on that path and about 5 miles before I got home. It died at least a dozen times, all while i was in traffic. I did get it there and said, "it is still in warranty, fix it, and got a lift home. I will post what is found.
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post #5 of 22 (permalink) Old 05-10-2019, 03:41 AM
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I have the ATAS. It surges in traffic but is OK at speed. However whenever the bike is parked in the garage the bike sings to me. The tank vents all the time with a high pitched whine. When I release the filler there is a rush of air. Not sure if its air flow in or out but the tank is at a different pressure to external pressure. That implies that the tank venting arrangement is restricted ?
The tank noise is loudest when the bike is hot and the heat is rising up and warming the tank after a ride
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post #6 of 22 (permalink) Old 05-10-2019, 04:18 AM
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Quote:
Originally Posted by BigKev View Post
I have the ATAS. It surges in traffic but is OK at speed. However whenever the bike is parked in the garage the bike sings to me. The tank vents all the time with a high pitched whine. When I release the filler there is a rush of air. Not sure if its air flow in or out but the tank is at a different pressure to external pressure. That implies that the tank venting arrangement is restricted ?

The tank noise is loudest when the bike is hot and the heat is rising up and warming the tank after a ride
Mine does exactly this. Would love to know of the slight flat spots when winding it on at motorway speeds can be fixed or if it's a case of "they all do that sir"...
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post #7 of 22 (permalink) Old 05-10-2019, 11:12 AM
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It is most noticeable in first gear for me. It just feels like the bike doesn't get power unless it is in 2nd+. But it still seems to have a serious flat spot ~4.5k for me

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post #8 of 22 (permalink) Old 05-10-2019, 01:05 PM
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Just throwing in another tally to the 'me too' tab. Same symptoms, trying to accelerate and having flat spots, or the bike just refusing to accelerate at all until the throttle is let off and applied more slowly. There have been a couple threads on this both here and on ADV about similar symptoms as well. Some people had blockage on their fuel pump from bad fuel or the rustproff liner in the tank coming off, but most of the time the symptoms occurred during hot weather, so an issue with the venting could pretty likely as well. Might make sense as to why this seems to be mostly an ATAS problem as well, with the new redesigned tank.
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post #9 of 22 (permalink) Old 05-14-2019, 05:51 PM Thread Starter
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A bit of an update, still no Joy. Talked to the shop yesterday and they ruled out fuel, but they don't know what the problem is, and it seems that mother Honda hasn't a clue yet. It runs strong and then just dies like it was turned off, but if you hit the starter it immediately starts and runs strong until the next death.

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post #10 of 22 (permalink) Old 05-15-2019, 08:02 AM
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As Motorwerx said, a few of us have experienced similar problems. Mine however came down to bad fuel and after a good clean out and new fuel filter, all came good. It was similar however in that when you switched the motor off and back on, it would run again fine for a bit. You can read more on my original post (subject - Rev limit (and fuel light) issue on ATAS in a very far away place).
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