F800GS miss fire / hesitation high gears low rmp - BMW F800 Riders Forum & Registry



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  1. #1
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    e / hesitation
    Hello all, looking for a bit of advice. Just completed a trip on my 2010 F800. Trip was just over 1500km here in Tanzania. On the final 200ks ( appox ) the bike seamed to develop a hesitation when pulling from low ish rpm in 4th, 5th & 6th. If you accelerate from mid range rpm no problem, lower gears slow / fast acceleration again not an issue. Bike idles well and starts on the button. I removed the in-line filter and it was dirty on the inlet side (dirty fuel here can be an issue ). I replaced the filter and ran it again over a few ks but the hesitation / miss is still there when pulling from low ish rmp in high gears. I know fuel pumps can be an issue in the heat but from previous experience when they go they tend to go completely, but I could be wrong. Any advice / ideas would be very much appreciated

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  3. #2
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    Welcome, Patickcarey. Naturally there could be a number of things that could cause your hesitation issue. The first thing that comes to my mind is you might have water in your fuel. Your fuel filter wouldn't catch that. Try dumping in some fuel cleaner like Drygas, Techron or something similar. Your spark plugs might need to be cleaned, adjusted or replaced, or your air filter could be dirty. No doubt there will be other thoughts from other members of the forum.

    It doesn't sound like the fuel pump to me. I have a friend who had a fuel pump go bad and his issue while that was happening was that his engine would die while running when the fuel level dropped to around the reserve level.

    Fortunately, I haven't had this problem with my F650GS. My only issue, and a very occasional one, was stalling while idling at a stop light. Interestingly, that hasn't happened since I replaced my old gel battery with a new and powerful lithium one.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

  4. #3
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    Welcome to the group. Sounds similar to an experience I had with getting some bad gas from a small town fuel station. No low end torque while accelerating and wouldn't pull steep hills unless I dropped down a couple gears. Maybe drain what you have or try adding a fuel additive to clean injectors/system and remove any moisture as Richard suggested. If that doesn't help, might be an air leak between the throttle bodies and intake manifold. Check for loose clamps, cracks in boots or loose hardware on the throttle bodies. The fact it starts and idles okay hopefully means it's nothing major, hopefully.
    Good Luck

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  6. #4
    AKBeemer's Avatar
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    What RPM are you calling low and mid in 4-6 gears?
    Kevin
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  7. #5
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    Thank you for the reply’s Gents, much appreciated.By low Rpm I mean around 3k. I’ll do as suggested and drain the fuel tank, put some fresh fuel on and add an additive and run it. If that fails I’ll pull the plugs and check the intakes / throttle body’s. I’m hoping it’s poor fuel as you’ve mentioned. I’ll let you know how I get on. Thanks again

  8. #6
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    So drained the tank and gave it a clean, bit of sediment in there and generally a little grubby, I wanted a spare fuel pump to carry and while the pump was out of the tank I could make sure the pump available here was the same spec, ended up fitting the new pump for peace of mind more than for anything else, I can carry the old one as a spare going on the assumption it’s still good. Flushed the tank and added an additive / injector cleaner. Bikes now running well and pulls right through all gears. I’m sure it was a case of dirty fuel or water in the fuel. The pump cost $65. Obviously genuine pumps aren’t available here, but it’s made in Japan, identical to the original. This pump is used on a lot of the small Toyotas. Thank you again for the advice

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  10. #7
    AKBeemer's Avatar
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    3,000 RPM is too low to try "pulling" in the upper gears. Your problem is likely that you are lugging the engine. You provided the solution in your original post. The problem goes away when you are in mid-range RPM or higher. 3,700 to 4,000 RPM is as low as you should go when accelerating in 4-6 gears.
    Kevin
    The Outpost, Silver City, Montana
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  11. #8
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    You could well be right, I didn’t consider this. I’ve had a number of other bikes on throttle body’s but I’ve never experienced this which is why I wanted to try and look into it. At the moment it seams to pull well from 3k upwards with out any issues in all gears.

  12. #9
    anjelli's Avatar
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    Quote Originally Posted by Patrickcarey View Post
    You could well be right, I didn’t consider this. I’ve had a number of other bikes on throttle body’s but I’ve never experienced this which is why I wanted to try and look into it. At the moment it seams to pull well from 3k upwards with out any issues in all gears.
    My F700 pulls well from 2,500 up since I installed the AX-FIED mixture controller. It would ping and stumble a bit under similar before I added the gadget. I know the F800 is tuned for higher RPM.
    FWIW, sounds like a fuel quality issue but changing out the pump was the smart thing to do.
    Greg

  13. #10
    Richard230's Avatar
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    My 2009 F650GS pulls well from 2K rpm on 87 octane fuel. Not a ping in sight.
    Richard - Current bikes: 2016 BMW R1200RS, 2018 16.6 kWh Zero S, 2011 Royal Enfield Bullet 500 Classic, 2009 BMW F650GS, 2020 KTM 390 Duke, 2002 Yamaha FZ1 (FZS1000N) and a 1978 Honda Kick 'N Go Senior. 

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  15. #11
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    welcome aboard Patrick, what is the model number of the pump you used? cheers mate (((-;

  16. #12
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    Centary Japan CFP 101 19L1,

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