HELP - K75 Fuel Pump Hum ?

Discussion in 'Old's Cool' started by Jman, May 13, 2004.

  1. Jman

    Jman a.k.a. FUglyK

    Joined:
    Aug 27, 2003
    Oddometer:
    921
    Location:
    Land of Flat and Straight EH !
    Help !!!

    I was just riding home from work and noticed a hum (buzz ? mmmmmmm sound) coming from the front of the bike that was never there before. It is noticeable (to me at least) with the helmet on and going down the road. Speed does not seem to affect the intensity of the sound. If I stop the sound continues, nothing seems to alter this hum.

    I put the bike up on the center stand and listened all over the bike and if I put my ear to the tank I hear it louder. The other thing that I notice which has never been there before is also a few drips on the driveway that smell like gas and seem to be coming from the vent hose that hangs down behind the right riders foot peg.

    Is something clogged? Is my fuel pump shot? The bike only has 47,000km on it. The only reason I am peaked at the moment is I am scheduled to leave a week from today for five days on the Blue Ridge and I don't really have the cash to spend at the dealer to get this fixed. The fuel filter has about 8,000km on it.

    Any help you could provide would be greatly appreciated.

    Thanks.
    #1
  2. Davo

    Davo BMW Uber alles

    Joined:
    Feb 8, 2004
    Oddometer:
    142
    Location:
    Melbourne, Australia
    How long have you owned this bike for? Do you normally ride with plugs? Lets rule out the possibility that you have been unobservant in the past (its amazing the things I have been oblivious of and then suddenly notice and thought how the hell could you miss that (eg some of my spouses character traits (no really I love her))) and work with the likely cause. Without hearing the sound but with the way you describe it sounds like you have one of two things 1. Almost no fuel in the tank (which makes the pump very loud and resonate nicely in the fuel tank or 2. A chunk of crap which has not quite managed to choke the pump completely but is making its life difficult. Go by the manual as far as removing the tank, gas filler mouth then the pump itself. No smoking please and take care of the rubber on the bottom of the pump and the filter gauze. It’s easy to tear. When my 75 did this it blew the fuse so replaced it, did the above and connected the pump straight to the battery for a couple of seconds and lightly tapped the unit with filters off to get rind of the FOD. Worked well and on my way. Stress not on you trip as all this can be done in daylight hours on the side of the road in under an hour. Make sure you carry some spare fuses as they will give up before the pump will. P.S. the pumps are bloody expensive so unless you have deep pockets I would not think about carrying a spare pump. They are very robust units. P.S.S. replace the fuel filter while you are in there as getting petrol all over you sucks even if you feel rather blissful while you are doing it.
    #2
  3. Jman

    Jman a.k.a. FUglyK

    Joined:
    Aug 27, 2003
    Oddometer:
    921
    Location:
    Land of Flat and Straight EH !
    Thanks for the hint Davo. I will take the pump out this weekend. I have had the bike just shy of 2 years. The tank is 2/3 full which is why the sound caught my attention.

    Pump is expensive? What part on this damn thing isnt? :D

    Thanks again.
    #3
  4. kentuvman

    kentuvman Been here awhile

    Joined:
    Jun 11, 2013
    Oddometer:
    105
    Location:
    Minnetonka, MN
    I own an K75s - when was the last time you replaced your fuel filter and same goes for fuel lines?
    Post #2 is also good advice.
    #4
  5. Tripletreat

    Tripletreat Been here awhile

    Joined:
    Dec 20, 2008
    Oddometer:
    670
    Location:
    Boise, Idaho
    There are fuel pumps on offer on eBay for as little as $20. Replace it; it's cheap insurance. If it fails on the road, you'll be paying a premium and the down time/inconvenience will certainly spoil your tour. Depending on the model/year, the tank may have a vent hose that exits on the right rear of the fuel tank. BMW changed the tank venting on the K-bikes, so you may wish to remove the fuel tank and have a look at what you have there.
    #5
  6. bmwrench

    bmwrench Long timer

    Joined:
    Nov 10, 2006
    Oddometer:
    3,358
    What year is your bike? '93 on pumps have been less durable than the earlier type.
    #6
  7. Jman

    Jman a.k.a. FUglyK

    Joined:
    Aug 27, 2003
    Oddometer:
    921
    Location:
    Land of Flat and Straight EH !
    WOW ! First, it is a really old thread but glad to see people are still willing to help. Haven't owned that bike in YEARS. Second, I don't even remember this happening. K75 was quirky but mostly reliable and I had lots of great miles on it. Currently riding K1600GT, it is just a little faster and more comfortable than the K75. :D

    Not sure how it ended up in the old school stuff though.
    #7