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1Back to top Go down    fuel pump widget? on Mon Mar 19, 2018 11:27 am

Beamer

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Hi,

can someone tell me what this little brass thingy hidden in a threaded hole is in the bottom of the fuel pump?

( top , right in photo)

This brand new Bosch pump, which I've only just bought has started making an awful noise. I think this widget should be centrally placed. Wondering if that is an indication of the problem.

TIA.


    

2Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 11:41 am

Crazy Frog

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This widget must be the high pressure relief valve.
It doesn't seem that it's seated correctly. Try to pull on it with a pair of long nose pliers, and see if it goes back flat.
The noise must be the fuel pressure leaking from there.


__________________________________________________
1986 k75, 1985 K100rt, 1985 K100rt/EML sidecar.
    

3Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 12:06 pm

Beamer

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Thanks, I was guessing it was a release value. What I thought was a threaded hole is a spring.

The noise I heard is consistent with a fast tak-tak-tak that may result from it clacking open and shut. Yesterday I had trouble getting home because the hoses kept popping off in the tank. At first I suspected a blocked fuel filter ( despite it being nearly new ) but I just replaced it and still have the over pressure condition. The old pump, which I put back in thinking the new one was defective, is leaking at the crimped top end. All this points to a serious over pressure problem. At that least means the old pump isn't dead, yet , and the new pump is probably not defective after all. Glad about that.

I guess I need to strip off the air box, flow meter etc to get at the fuel pressure control valve. Arg !

Do these things often go wrong? I've not heard of that before.

cheers.

    

4Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 12:38 pm

Crazy Frog

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@Beamer wrote:Thanks, I was guessing it was a release value. What I thought was a threaded hole is a spring.

The noise I heard is consistent with a fast tak-tak-tak that may result from it clacking open and shut.
The "tak-tak-tak" noise can come from the one way valve on the return line (This valve is directly mounted on the front of the tank.

Yesterday I had trouble getting home because the hoses kept popping off in the tank. At first I suspected a blocked fuel filter ( despite it being nearly new ) but I just replaced it and still have the over pressure condition. The old pump, which I put back in thinking the new one was defective, is leaking at the crimped top end. All this points to a serious over pressure problem. At that least means the old pump isn't dead, yet , and the new pump is probably not defective after all. Glad about that.

I guess I need to strip off the air box, flow meter etc to get at the fuel pressure control valve. Arg !
YES you will have to investigate an over pressure. Before starting to dismantle the airbox, first check that the hose coming from the throttle body and going to the fuel regulator pressure valve is not disconnected at the throttle body.

Do these things often go wrong? I've not heard of that before.
Yes they do.

cheers.


__________________________________________________
1986 k75, 1985 K100rt, 1985 K100rt/EML sidecar.
    

5Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 1:07 pm

Beamer

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thanks for the tips.

The vacuum tube with the spring protection is in place and maintains a depression when I suck on it. Good idea though I had not thought of that.

There is no return flow to the reservoir there seems to be a blockage after the injector ramp. I think this may account for the dastardly split I previous had between pump and filter. Presumably a fabrication weakness and that was the weakest link at that time. As I fix things the next weakest link gives out. I've only just found out that it was a pressure problem all along.

Looks like I need to strip the air box etc. Very annoying.

Thanks for the help.

    

6Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 1:37 pm

Beamer

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Is there anything that can be serviced/cleaned on the press. regulator, or is it just a case of replacing it?

thx

    

7Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 1:41 pm

Point-Seven-five

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Please excuse me, but my psychic powers are running a bit low today, so I can't discern what model or year your bike is.

In any event, if it is an early model you may have a plugged check valve in the return line. It is screwed into the bottom of the tank where the return line connects.


__________________________________________________
Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

8Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 1:42 pm

Crazy Frog

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@Beamer wrote:Is there anything that can be serviced/cleaned on the press. regulator, or is it just a case of replacing it?

thx
NO. It's a sealed unit.
But....
If you are ready to remove it, you can always try to remove the small hose from the throttle body and blow some compressed air into the fuel regulator. Sometimes, it work. Don't go over 20PSI otherwise you could blowup the hose. They are not made to sustain high pressure.


__________________________________________________
1986 k75, 1985 K100rt, 1985 K100rt/EML sidecar.
    

9Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 1:48 pm

Crazy Frog

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@Point-Seven-five wrote:Please excuse me, but my psychic powers are running a bit low today, so I can't discern what model or year your bike is.

In any event, if it is an early model you may have a plugged check valve in the return line. It is screwed into the bottom of the tank where the return line connects.
I second your statement .75
I cannot see that happening, but it's easy to check. You just have to remove the return hose and unscrew the valve from the tank. As I was fed up to listen to the "tak-tak-tak", I removed the ball and the spring from it.
Somewhere on the forum Sidecar Paul had removed the valve too and inserted a tube going to the top of the gas tank (Internally). This way, the gas is not pouring when you remove the hose.


__________________________________________________
1986 k75, 1985 K100rt, 1985 K100rt/EML sidecar.
    

10Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 2:01 pm

92KK 84WW Olaf

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Possible the two front pipes on the tank are connected wrong way round?


Regulator sitting in my parts box....you only need bottom half of the airbox off to get in there. The lower half has two usually seized Allen bolts down to the top of the engine.

But check your vacuum lines. Early Ks up to some time in early 85 have one at the front as well [my RT is 84 and has one], to a fuel pressure sensor. Don't worry about the sensor, it does nothing. But the vacuum line needs to be good or else plugged with a cap same as the vacuum take offs.

Loss of vacuum will give you over pressure.


Did you buy a genuine Bosch pump....?


__________________________________________________
1992 K100LT 0193214 Alaska Blue 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Mystic Red 58,645 now 74,700 miles
    

11Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 2:10 pm

Beamer

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1985 K75C

I've got the thing off, so I'm going to give it an hour in the ultrasonic cleaner and maybe some gentle heat. Not much to loose at this point.

I've already established that there is a blockage before it gets back to the tank.

I have some Carburaigle hosing that is good for 10 bar, that will allow be to give enough to open it up if it's not completely jammed.

I'd guess it's just a spring loaded valve, is that right?

cheers.

    

12Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 2:20 pm

92KK 84WW Olaf

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I don't get how there can be a blockage except for a broken up fuel pipe as they can disintegrate. After that I'm thinking something misconnected.


__________________________________________________
1992 K100LT 0193214 Alaska Blue 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Mystic Red 58,645 now 74,700 miles
    

13Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 3:18 pm

Beamer

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I had all sorts of crap in the tank when all this started, so a blockage is possible.

How does "something not connected" result in no fuel return? If I have 4-6 bar from the pump, it should blow off and return something, right?

OP:

This brand new Bosch pump, which I've only just bought has started making an awful noise.

    

14Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 4:46 pm

92KK 84WW Olaf

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I took it from the post that although you had pressure there is also no fuel is returning to the tank. If you disconnect the return pipe at the front of the fuel rail and pressurise the system you should get a spray. Messy but its a quick check.

There is also a mesh filter for the pump........as well as the metal fuel filter.


__________________________________________________
1992 K100LT 0193214 Alaska Blue 101,000 miles
1984 K100RT 0022575 Baja Red bought 36,000 now 89,150 miles
1997 K1100LT 0188024 Mystic Red 58,645 now 74,700 miles
    

15Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 4:53 pm

Crazy Frog

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If the fuel pressure regulator is blocked, nothing will go back to the tank.
To compensate, the built in high pressure regulator on the pump will release pressure in excess of 66PSI.


__________________________________________________
1986 k75, 1985 K100rt, 1985 K100rt/EML sidecar.
    

16Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 5:22 pm

Beamer

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Olaf wrote:I took it from the post that although you had pressure there is also no fuel is returning to the tank.
That's correct.


CF wrote:If the fuel pressure regulator is blocked, nothing will go back to the tank.
That is the assumption I've been working on since I noticed it was a pressure problem. The bike runs, so I know it's not before the injector ramp. That means either the regulator or the pipes either side. I can blow through the return pipe, so that's clear.

After an hour in the ultrasonic bath the regulator is shining like new. I'll see whether it works any better tomorrow.

    

17Back to top Go down    Re: fuel pump widget? on Mon Mar 19, 2018 5:59 pm

Point-Seven-five

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#19 on this drawing p/n 16 12 1 455 348 U.S. price is $8.62


An owner on the MotoBrick forum had a really ugly one come out of his tank last week. Was preventing almost all the return flow to the tank. If pulling the return hose shows lots of flow, this is your problem.


__________________________________________________
Present:
1994 K75RT
1994 K75S
1992 K100RS

Past:
1982 Honda FT500
1979 Honda XR185
1977 Honda XL125
1974 Honda XL125
1972 OSSA Pioneer 250
1968 Kawasaki 175
    

18Back to top Go down    Re: fuel pump widget? on Sun Mar 25, 2018 3:24 pm

glennpm

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The brass post from your picture is part of the internal pump over pressure valve. Its like a needle valve. It should be centered in the hole.

If you decide to replace the pressure regulator, search by the Bosch number and you'll find some reasonable prices. I was searching a couple of weeks ago when I thought I may need one for my 87 K100RS. Bosch part #0280160200 for early K's but verify for yours.

    

19Back to top Go down    Re: fuel pump widget? on Sun Mar 25, 2018 3:43 pm

Beamer

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Thanks Glenn, that ref may come in handy.

The old unit seems very solidly locked closed. 1 hour of ultrasonic bath and even a hammer and screwdriver up its 'ole did not free it. I ended up swapping with a spare I had on a non running bike. Now blows off at about 2.3 bar.

Runs pretty well through out the rev range but still has a tenancy to stall at junctions. Very annoying.

Fiddling with the air flow meter bypass does not help much at all. With all the crap that went round I may have an injector which is a bit sticky at very low feeds. I'm going to have to dig a bit deeper.

Main thing is I'm mobile. Wink

    

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