I've have been offered a 1995 BMW K75LT for a resonable sum but it has on issue with it - a loud whining fuel pump (I know they all whine so some extent). The bike has to be bought with this fault.

This is a new fuel pump as the owner replaced the original four weeks ago (himself) as the previous one had similar symptons. He unfortunately did not replace any of the fuel filters (one of which he said has a tear) whilst doing so. BMW have said that the failure to replace the fuel filter has ruined the new pump and another is required.

Any thoughts? Does this sound right? Could it actually be another problem not the fuel pump? I want to purchase this bike to ride through the Middle East back to the UK and would like something that isn't going to need continual repair. I also have an R80G/S bought for the journey but it is unlikely that this is going to be in a reliable condition in time so this is the next choice.

Thank you.

If the pump is 4 weeks old and is whining...you're fine. Make sure you get the paperwork to prove that BEFORE he sells you the bike.

If you choose to buy the bike, ask for the old pump as well as promptly replace the filter. Also ask the previous owner what other work he personally has done to the bike...and make sure you check it...or post it on here. The final drives splines...if not properly greases...are a weak point on that bike.

Anyways...filters are cheap...you don't necessarily need the BMW specific one...here are some alternative choices...

Triumph Stock - T1240850
AC GF61
BMW - 16 14 2 325 859
Fleetguard FF149
Fram G2
KNECHT MAHLE KL145
Motocraft FG-2
Napa Gold 3032
Purolator - F20011
Wix 33032

__________________
edde
93 BMW K75s
www.motoedde.com

MotoEdde, thanks for the quick reply. I have seen the receipt for the pump so pretty sure it has been replaced as he said. Good point about seeing the old fuel pump.

Yes done a fair bit of internet research on the bike so know of the spline issue (though owner doesn't). The bike has apparently a full service history (and only 25k km) but I will check this with the BMW service centre here.

Could you just explain why you think the pump is fine please. The noise the pump makes is so loud as not to be normal. Can a clogged/damaged fuel filter really cause (a new) pump to make so much noise?

Thanks

You have to understand the circuit your fuel travels...

Fuel flows from within the tank into the fuel pump via a pre-filter attached to the bottom of the fuel pump and then pushed through the fuel filter into the fuel rail. From the fuel rail, the necessary fuel then flows into the injectors and the remainder returns to the tank via the fuel pressure regulator and the pump cycle begins again.

Since the pump is a Positive Displacement type, it pumps at a constant rate no matter what, and the fuel pressure regulator returns the excess fuel back into the tank. You have filter before the fuel pump, one after the fuel pump, and one inside the fuel injectors.

Considering the bike is running...and its been only four weeks...the MOST important question would be...how many miles did he put on the new pump? And did he bother to replace the rubber mount/vibration dampener the pump sits on inside the tank?
If he didn't...then the rubber dampener the fuel pump sits on could have deteriorated and got sucked into the fuel pump. THAT my friend would be my biggest worry...

Inside a K75 fuel tank...
Search results for k75 fuel-filter

Part #3 and #4 in the picture below is the fuel pump mount and vibration dampener...check and see if these BMW part numbers are on the receipt when he purchased the fuel pump...OR when these were last replaced. If these are original...their deterioration is probably caused the original fuel pump/filter to get clogged...and is causing the new one to as well.

[url=http://www.realoem.com/bmw/showparts.do?model=0572&mospid=47908&btnr=16_0243& hg=16&fg=05]RealOEM.com]RealOEM.com

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edde
93 BMW K75s
www.motoedde.com

Many thanks MotoEdde for the reply. Only briefly looked at the receipt, but pretty sure it was only for the fuel pump. He has openly admitted to not replacing the two fuel filters so expect the damper will not have been replaced either.

I don't mind replacing the furl pump with a third if need be (the purchase price of the bike reflects this). What I am more concerned with is that the whine is symptomatic of greater problems I only uncover when trying to get it fixed (knackered injectors or something).

Mileage on new pump is negligible he has only done 700km on the bike in the year he owned it (he also owns two other bikes).

Can't see the flickr photos at the moment (site banned in UAE) so willl have a look at home through the V*N this evening. Once again thanks for the advice from your website looks like your K75 has been well used.

Worth the double check. As far as your concern of the fuel pump noise being a leading indicator to bigger issues...I would say the following.

I think you're lucky that the guy hadn't bothered changing the filter...as it probably helped save the fuel injectors from getting clogged. Remember the fuel flow circuit! So I don't think you'd have to worry much about the fuel pump IF its 4 weeks old AND that rubber dampener/mount is replaced in a timely fashion.

The concerns you may want to have is of any prior work done by this owner...as he clearly isn't a decent enough mechanic despite his valiant efforts. Find out what work he's done prior including local shops.

With the K75 bikes...the best thing you can do for these bikes is ride them...

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edde
93 BMW K75s
www.motoedde.com