I've got my 1985 K100RT, that has been sitting for close to 15 years, running well. I've only been on the road a few times (~100 miles) and I really like it so far. The bike has really smooth acceleration, is powerful, starts instantly, idles perfect, stops well and has no major issues - except, the fuel pump? is making a whirring and repetative metallic ticking/clicking noise. At idle first off it is quiet, then as I open it up the noise starts. After riding a while and I pull over to let the bike idle, I would call it a moderate whirring and sometimes ticking. The noise seems to go away at high speed (maybe I just can't hear it with wind noise) and it also seems to go away or is quieter when I decelerate. I've flushed the tank, cleaned the fuel pump screen (which was clean initially), put in a new fuel filter, and the dampening collar/ring are good and solidly in place in the tank. I've opened the gas flap to listen and it seems to be coming from inside the tank, but I'm not 100% sure it's from the pump. I'm thinking of replacing the fuel pump, but I'm not to sure that is the cause of the noise. Could it be the fuel pressure regulator? Your thoughts or ideas on this annoying noise? Thanks.

As a suggestion, start the bike and do what you have to do to get the clicking started. Then place a looooong screwdriver into the tank and onto the fuel pump (be careful of the electrical connections on the pump) and put your ear on the handle of the screwdriver (yep, a stethoscope).

Hopefully you can identify if the noise is coming from the pump.

Tell us what the result is.

is this the dreaded fuel return valve spring issue ...i seem to remember reading that bmw removed the spring on the return side of the fuel rails - tank return ....so as to eliminate noisy valve operation ...i think the return valve is actually a ball bearing held closed by a spring
maybe if you extend the return tube so that you could manually hold the pipe and let the fuel into the tank would proveit one way or another

my two cents ....others may well know this issue better


thats a way good tool for diagnosis blakey .......good one mate

Nice little trick there Blakey! I gotta remember that one.

OG

I remove the valve on mine (because of the noise) and installed an in line shut off valve made for a snow blower.

Thanks for the suggestion on the screwdriver stethoscope. It really worked well. I opened the gas flap and stuck a screw driver against the fuel pump. It is not making the noise. It seems to be coming from under the fuel tank on the front left side. So I removed the left rubber knee guard, then I stuck the screwdriver stethoscope all around on the left side. The fuel rail makes a ticking, but it is not the same noise and is not related to the deeper more solid noise that seems to be coming from a position higher and more up towards the front left. I can't seem to see the fuel pressure regulator from any angle to get my screwdriver on it. I'm still puzzled. How do I diagnose the spring or ball bearing issue in the fuel return valve? Thanks!

the fuel return valve sits in the tank ....its actually built into the return hose coupling to the tank itself ....exactly at the front left of the tank ....(not the regulator , bolted to the back of the throttle bodies and behind the air filter box looking from the other side ). i think the output of the fuel regulator is more or less a pulsing type of action when operating and thus rattling that little ball bearing around a bit .

i believe the hose coupling can be removed from the tank for inspection - maintrnance ....obviously you might wish to remove some of the fuel first .

there is a diagrame of the tank inards and parts on here somewhere

but also just a note worthy of mention ....on my bike the fuel float device ...part of the fuel gauge sender mechanism inside the tank ...often clanks on the sides /top of the tank as the fuel moves around inside ...more prevalent as you put more fuel in and quite anoying when you are just sitting more of less still whilst on the bike ...could this be the louder and deeper clunk-ting that you are hearing as well?

charlie99 Thanks! I just pulled off my left side lower fairing to start to remove the tank and get into the fuel return valve. Once I could see the valve under the tank, I started up the bike, put the screwdriver stethoscope up against the value and it metallically howled and buzzed in my ear. The mystery noise has been solved. With this knowledge in hand, I dug into the Haynes BMW K100 manual and found the repair/fix on page 135 under fuel return valve. Basically they say to remove the valve out of the bottom of the tank, lever the top rim and prise out the cover disc. Once that's done withdraw the spring and refit the disc back into the valve top and peen over the top of the valve to secure the disc. They suggest leaving the ball bearing in. Crazy Frog above in this chat series suggests removing it and placing an in-line valve that can shut off the fuel if the tank is removed. I think I'll look into an in-line valve to replace the whole fuel return valve and then throw the noisy bastard in the trash.

lol....good find bandon ,,,,,, whilst your there ..get the part numbers for the inline valve ..mine needs doing as well ...giggles ....ive known about it for some time but i have left the bottom covers off my rt so as to allow easy access untill i have solved all the issues ...besides .after replacing my fuel pump and hoses quite recently ...its a good thing to hear that the system is circulating aok .....im not paranoid ...but i do have my doubts , after more than a few hundred killometers on the old gal im pretty confident that issue is resolved ....next !!!!!

thanks for replying btw .....its good to see a result ...and enchorages us all a little bit more to try and help our k bike friends

i guess "what goes around, comes around" huh ?

thanks to all

Here is where the return valve is:



I am planning (for the last 3 years) to remove the valve, and modify it.
Basically, what I want to do is make a bushing where I will solder a pipe going toward the top of the tank.
I will then press the bushing inside the valve.

hmm ....good idea bert

that might be a better solution than a valve

Frog and 99, Thanks again for the help on resolving the cause of "the noise". I couldn't find a good in-line valve, so I did the Hayne's fix of removing the spring, then put the tank back on. The ball bearing then created a new noise, so I pulled the tank again and removed the ball. No noise - as it should be. But now I must drain the tank prior to removing it. This valveless system is OK if I'm at home where I have a siphon and gas cans to put the fuel, but not the best for emergency roadside repairs that require removing the tank.

In the Haynes book, pg 135 they talk about how the fuel return valve was deleted completely with the K75S models in mid-1986 and the valve was replaced by a long stack pipe which passes up to the top of the tank (similar to what Crazy Frog refers to above). Has anyone converted their old fuel return valve for the newer tall stack pipe? I'm wondering if it would work in my 1985 K100RT?

That is exactly what I will try to do and I explained in my previous reply.
The newer models have the stack pipe but it's soldered to the tank.
The best way to deal with this modification on a 1985 bike is to use the body of the old valve and press a bushing with a pipe soldered on it.
For the shut off valve, I used the one from a snow blower but a valve from an old fashion lawn mower should work too. They are usually the "in line" type, and because of their proximity to the engine are heat resistant.
Here is a page with inline valves. The one that I use is the Briggs and Straton one . Yes it's a hard plastic valve!. Remember, this is a return line and unless the passage is blocked, you should not have any pressure (just high flow)


CF

Crazy Frog, Great suggestion with the lawn mower in-line valve. I'll pick one up next time I'm in the city. Seems like there is no need for a tall stack pipe on the body of the old valve if I install the in-line valve, or is there some vapor lock issue or some engineered need to take the return fuel all the way back to the top of the tank? Thanks!

i guess the value of taking the stack to the top is,--- so that you dont have to remove fuel when taking the tank off ......keepin it simple
its got my vote

I'm liking the sound of this guys. Please make sure to post pics if/when you do modifications.
Thanks!

OG

Does the fuel return valve make noise because crud has gotten into it from sitting to long? Can it be cleaned out? Or is it just worn out? Any thoughts? Has anyone had sucess doing a cleaning?



Thanks Dino

dino ...the valve is a spring loaded ball bearing ....the pulsing nature of the vacume feed from the throtle bodies to the regulator causes this weird noise ....later models did away with the valve completely and installed a pip direct to the top of the tank .



one of the sugested mods was to take out the spring completly

Thanks Matey I had saw those posts. Just wondered if it was dirt or loss of spring life. Will just eliminate the spring and ball. if the gas gets loose i'll run like crazy to get away before the flames start!

i think were waiting till someone does the mod to the older bikes ....personalllly i have left mine rattle away ....after my fuel pump died , it was always a welcome thing to hear ...but now in sure its all good ill be looking to do a modification and post the results ...

What a relief to read these posts. I've got exactly the same noise. I really like the in line shutoff idea. Just had the tank on and off several times and had to balance it across a wheelbarrow with a gas can under to catch the dribble of gas that just wouldn't stop. It's just nice to be reassured that that sound isn't my fuel pump eating itself! Thanks guys.

Pulled my valve out today also. You have to work out the flat piece of metal holding down the spring and ball. The ball was shiny on only one half. (Fuel tank side).

The other half was a hazey, and had a rough feel to it. Decided not to install fuel shut off.

Exiting work if you forget when you work on tank next time. HAH!



Dino

Mine has had the mod done and more or less stops the fuel but no longer rattles. The amount of times I've removed the tank, you need either a working valve or a manual tap.

Hi Geordnz,

I always drain the tank with my fuel pump before removing the tank when I have to pull it. I was not aware of the return valve until it was discussed on these web feeds.

I know it sounds crazy, but I wonder how much BMW saved by not putting on a real fuel shut off valve?

Thanks for the warning.

I had another bike that the shut off valve was defective and the gas ran until i stuffed a bolt in the hose. That's why I allways drain the tank.

Since removing the spring and ball there is no annoying noise now. Hooray!

Thanks to all you members.

Just came across this thread, is the purpose of the velve to stop fuel coming from the tank if its removed? Fitting a shut off valve would surely result in somebody starting the engine with it closed with some interesting results although the relief valve on the pump should blow before anything else!! My tank has the pipe entering at the top so the end result is similar to whats in the later models of bike tank. You could always remove the original valve and fit one of the many one way valves available for cars. Philip

Or fit a piece of fuel hose on top of the defunct non-return which loops against the top of the tank.