1980 gs550e - fuel tap / tank noise

[ukjules]

I have a bike as above and when ever it gets near to reserve a tapping sound is heard
in the tank?

It must be vacuum pulses from the petcock creating this sound amplified through an emptying tank ?
(Even with the tank beside the bike with a long line the sound is still present so it is not
engine / frame.

The bike has a fuel line to petcock and a vacuum pipe to carb 3. Standard RES and On only (no prime)
The internals are fine and it works perfectly.

Does anyone else have this ?
I wonder if it is doing damage when i let the petrol level get low.

I attach a diagram of my petcock - the original.
it has no prime and to fit on my bike due to access the fuel and vacuum pipe must point forward or to the right not backwards.
(Anyone know where i can get a petcock with prime as above ?)

 

[Agemax]

if you have a tank gauge then it could be the float hitting the inside of the tank when the level gets low

 

[ukjules]

No tank guage , standard.
It is the petcock and vacuum pumping ...
I just wondered why only my bike does it ?
Always has ... Always will.

I am convinced all other 1980 GS
With only Res / on on petcock must ?

 

[tatu]

Try putting the lever to prime position and blocking the vac pipe?

 

[ukjules]

Aha .... Yes no prime on this tap as per diagram
it is the standatd one.

It makes a rattling sound as it gets near to Res.
Switch to Res disappears.
Disappears when full too.

I am just readying the bike for a " tour "
and would so like a tap with prime but
The feeds must point forward or inwards.

I'll go as is as not an issue just a noise ?
I can't see how others with same tap do t get it .

 

[Guest]

I would love a petcock that did that. Most of the other '80 models got a petcock without a lever with a little nylon screw slot that was run (horizontal) or prime (vertical), no reserve. My tanks were in terrible shape so I got a '80 NOS tank for my '78. Does your petcock have a 50mm bolt spread? Mine looks like this (https://www.z1enterprises.com/petcock-vacuum-50mm-bolt-spacing.html), it is a KL number but is identical to the stock petcock.

 

[ukjules]

For the 1980 gs550et - the petcock plate bolts from end to end is 50mm.

On my original as per diagram (earlier in thread) there is no prime. Vacuum only which makes it hard to start
after being left for a while. Also makes the sound in question when nearing reserve.

I attach a petcock that i used on my last Europe trip borrowed when mine disintegrated.
It is off a suzuki but i dont know what.
50mm outside to outside so fitted fine but the pipes point the wrong way thus i had pipes
coming out around the outside of the bike.
It is however the type i need - has all the logical elements anyone using as bike needs when out
on the open road. Why oh why are there not more of these types being made ?

I need one like this but the pipes pointing forwards or near as.

 

[ukjules]

And just for info - my standard one - with just on/off (no prime)
but pipes pointing in the right way for use on my bike.

Note - I think center to center is 44mm using m6 bolts
to attach to tank.

 

[roeme]

(...) Why oh why are there not more of these types being made ?

I need one like this but the pipes pointing forwards or near as.

View attachment 51583

'79 550 petcock might be what you're looking for; see this post of mine for a few pictures. Not sure about the bolt spacing though, didn't take any measurements when I was cleaning mine.

 

[Guest]

This one might be interesting to you then. I was hoping it would fit mine but my measuring method was off a bit the first time and mine was 50mm. https://www.z1enterprises.com/petcock-kz1000k44-m44-p-kz1100-kz650h-kz750h.html

 

[ukjules]

Thanks for info.
@oldvet
That one looks ideal IF the petrol line can be moved to point
forward. But to me that looks exactly what everyone wants
for peace of mind on a long journey ( the prime function )
I'll email them for exact details.

@roeme
I'll read but if spacing right , pipes point forwards
and there is a prime it will do.
I'll add 1979 ones to my search.

That new one does look ideal though if it fits.
I'll see how helpful they are when I email them ...
Will report .

 

[ukjules]

I have emailed Z!enterprises about that petock.

If it is 50mm outside of hole to outside of other hole
(44mm center to center near as damn it) and if the vacuum pipe can be turned to point forward.

If this is so - this looks good.

Do comment if anyone else know "the" place for petcocks , but petcocks with a prime function !
and pipes pointing forward or in.

I attach pic of said petcock

 

[tatu]

I've not heard of taps causing noise and wonder if the diaphragm 'panting' back and forth wasn't the problem that started back on your last trip. Restricting down the vac hole orifice will control that, are the vac pipes in the right place on the carbs?
What about a Pingle? just a straight non vacuum tap?
Sorry, previously I didn't realise you didn't have 'prime' position.
These vac taps a serious nuisance when they get older plus they a pest when trying to restart when the bike's been standing. When I open mine next time I will look to see if I can modify the thing so that it's only on and offable, moins vac.

 

[ukjules]

You are right , that panting in the end broke the
petcock internals causing petrol to flood
into cylinder 2.i am sure of this.
I am concerned to start trip 2 with exactly the same issue
albeit being in its infancy.

It is definitely the tap, the panting vacuum.
I can put the tank 6ft from the bike with a long line
and the petcock rattles away echoed by the tank.
Clank clank clank ...

I have one that works fine but the pipes point the wrong way.
This is the one I got in Amsterdam with a prime.

Vacuum goes to cylinder 2.

Wonder if the vacuum pipe is sealed well enough ?
Shall I remove tank side and block off and try ?
Someone else must have had this clanking ?

 

[tatu]

The diaphragm isn't designed to flap back and forth like that it will knacker out in no time. you must find out why you're losing vacuum in cycles.

 

[Agemax]

what carbs have you got, BS or VM, your first post you say vac pipe is on #3 carb and now you say its on #2 carb, so which is it?

 

[ukjules]

Petcock vacuum goes to carb 2
Bs carbs

(I won't be near bike till later today )

I'll do some tests later and strip the
petcock. ( I'll also re for my one I had to use on long trip
in an emergency as can't remember if that too had the noise issue )

But for years it has done this .
But the diaphragm in the petcock must
open / close almost every second.


Note:
The bike runs like a dream. Tuned spot on.
Does not have a fuel filter (no room or it would)
Totally standard bike.

 

[tatu]

No, when there is vacuum then the valve opens, when there is no vacuum the valve closes, ie one cycle per engine on and engine off.

Have you tried opening the fuel cap to see if the clanking goes away?

 

[ukjules]

I will redo tests later this afternoon!

I have taken the fuel cap off a d clanking remains.
Let me check again ...

Re the petcock from z1 enterprises.
It looks to fit as they have emailed. Same dimensions as mine
I'll check prices etc and might try it .

Tests:
-Good sealing vacuum pipe
-Fuel cap off , running along
-Vacuum pipe off but blocked off tank end ?

Any other analysis I can do this eve .
I can also strip it and check internals.

 

[ukjules]

Bare with - I have some success but using another
fuel tap.

I'll update later with pics but my internals
on the petcock were broke again , the metal bit on the diaphragm

pic is original petcock