Fuel tap petcock vent pipe leak

[didge]

I’m probably repeating, and I apologise for that, but I’ve looked and been unable to find the answer, so, here goes.

Rog has recently done some work on my bike and it now runs the best it ever has in all the years I’ve owned it (thanks Rog), that is, until the tap played up.

I tried all sorts of advice given here on the board, blanking off the on position, etc etc, eventually I got a GT type tap, all be it a Chinese one, but still it wept fuel flooding the carb making it impossible to start again.

I’ve just realised the pipe on the right of the tap going to the tank is in fact a vent, but there’s fuel flowing freely from it.

My Question is, can that vent be blanked off or is it crucial to the bikes running ?

[wayne]

If the vent has rusted and got some leaks into it, fuel will pour down the pipe into the fuel tap as if you're on Prime.

But I'm not sure what happens if you disconnect it and how essential it is.

[mick695]

I replaced the original fuel tap with a genuine Suzuki tap, part number 44300-45011 as suggested by others on this topic. It works well, only problem is the tight routing for the petrol pipe to the carb, but I can live with that.

It also requires that you blank off that vent pipe as the new petrol tap has an internal vent.

I've had it fitted for nearly a year now with no problems...

[didge]

I’ve currently using one of those GT750 taps Mick, but if that vent is the only thing stopping me using the original tap I’d rather go down that route, I’m still keen to know if the vent can be blanked off or is it crucial to the bikes running ?

I even wondered if it would work if I blank it off at the tank and then run a vent from the tap, to go under the tank alongside the frame ?

Where are those that know ? (I’m hoping to do it at the weekend.)

[wayne]

Given Suzuki went to the trouble of having a long internal vent pipe I'd take it as given that the tap needs the vent.

I reckon your idea to blank it off under the tank and then run a tube along the frame may work.

Someone at one time or another has been the "first" to solve problems on the bike Didge (and then write about it). This one is yours. Please report back.

[didge]

Oh lord, no pressure then. 😂

[HGH 770N]

If carb is flooding/Dribbling from are inlet this is more likely to be the needle/seat not seating properly.
This is common even after fitting new ones after storage i have known them pass especially if pet tap “cloverleaf “ rubber is not seating good and gravity of fuel in tank pushing.
I had this issue years ago and added a small inline pet tap that solves this issue.
Try removing pipe from carb inlet and see if fuel passing when tap is on “on” or “res”
If vent pipe is passing this could also enter foreign parts from tank into the tap as it doesn’t have filter internally.
I have used GSX Katana taps and not using vent .
Provided your pet cap is venting good i see no issue in blanking vent off essentially if it has perished inside and passing fuel.

[hudson]

  Just to add my experience, the vent stand pipe in the fuel tank is there to avoid pressure build up in the fuel hose  when the engine is shut off and heat from the hot engine causes expansion of the fuel in the fuel hose that is trapped between the needle & seat in the carb. and the closed petcock. This would force the needle off the seat and could cause a flooded start situation. But not as bad as a leaking needle & seat. There will be fuel in the vent line , especially with a full tank, when disconnecting vent from the bottom of the tank  you need to let it drain for a 5-10 seconds first so you can then see if it is indeed leaking internally. I have not seen one leak internally before but that does not mean it can't happen.  The vent should have a filter inside the cover on the bottom of the petcock. I have seen this filter missing and is the same as the filters inside the tank and they are available from Suzuki. As for leaking needle &seat I had one that was leaking and looked perfect, it turned out to be the little red seal washer between the seat and carb. and it looked perfect even under magnification. I have posted else where on this forum about how to repair the stock petcock/fuel tap. There is a lot of fuel in the vent stand pipe and fuel hose and will cause quite a mess if the carb. is leaking. But it will stop after a day or two if the petcock is not leaking depending on how bad the needle and seat is leaking and how full the tank is because a full tank will have more fuel in the internal vent pipe. Leaving the bike on the side stand should keep the fuel leaking on to the floor and not into the engine.

Didge,  Please let us know how this turns out. 

Brian

[didge]

Thank you Rog and Brian, those answers make a lot of sense.

I am now thinking it’s less likely to be the breather feeding fuel in.

It’s driving me nuts, I’m really no mechanic and I’ve not been able to use the bike for weeks now. :-(

[timpa136]

May 11, 2021 11:52:49 GMT -5 didge said:

Thank you Rog and Brian, those answers make a lot of sense.



It’s driving me nuts, I’m really no mechanic and I’ve not been able to use the bike for weeks now. :-(

Please take precaution not to let the flooded oil set with bad gas. Take precaution to disable the spark and pull the CDI connector when clearing a flooded engine. In meantime there are hose clamps available .




Keep us posted.

Regards,
Tim

[didge]

To update this Tim, I tried clamps but when they were taken off, the pipe remained pinched where the clamp was, so….
I thought all this grief is to bypass the tap problem, it’ll be easier to tackle the tap.

All the tap parts went into the ultrasonic (again) and all the rubbers replaced, the diaphragm was cleaned, (they’re sturdier than you’d imagine), but it still leaked.

This next bit sounds a bit bodgy, bear with me, I put fine steel wool on a big Philips screwdriver and, using a back and forth motion, (like when you grind valves in) cleaned the area where the diaphragms small rubber O ring sits, and then replaced that O ring with the Kawasaki replacement suggested elsewhere on the board.

Truth is, that tiny little rubber ring can cost you £50 from the states, but if it solves the problem, which it did, it’s worth every penny.

[timpa136]

Thanks for the method of repairs and happy you are back in business so to speak.

Tim