TOPIC:

petcock would only work if bike is running. does`nt matter how many lines are hooked up.

@ all,

I used to have the vacuum petcock installed with just one vaccum hose. It worked. At a certain time I however had the suspiion that tha machine wasn't working "like usual" and it turned out that the membrane of the petcock had been defect. The reason could be (I do not say it is like that) that I had only one hose installed. I am working now with tow to avoid the before mentioned pulses and to create a rather steady vaccum.

Now I do not claim what I had been told is the absolute truth, but need to admit it sounded logic to me and I feel much better with thwo hoses.

regards,

Holger

I can imagine only having one cylinder to the tap giving the diaphragm a hard time with the pulsing at low revs.

This whole topic has taken me back to the early 80's with a problem on early Suzuki GSX1100's when I was a young Bike Mechanic in a dealership.

There was a spate of GSX750's & GSX1100's that were running very hot at low revs & even reports of valve & piston damage caused by overheating.

The cause of the problem was (as I recall) the pulse from the intake manifold pipe feeding the vacuum tap was not regular or strong enough at low revs & after prolonged periods created gradual fuel starvation due to not letting enough fuel thru the petcock...........making a LEAN mixture & causing the over-heating.

I am almost certain the fix was to use a T Piece in the pipe to the petcock & split it to TWO separate inlet manifolds to DOUBLE the pulse.

Pete F

Got my used GPZ900R petcock in the post today (Ebay strikes again!).

It is a very well designed part & looks to be an ideal upgrade for our beloved 1300.

The problem I have had in the past with finding a good updated suitable replacement for the original was the pitch between the 2 mounting holes on the base of the tank & the fact that the fuel pipe feed needs to come out of the bottom & backwards.
All of these requirements make using a petcock from most other bikes impossible, as they dont have the correct pitch or the fuel pipe outlet is in the wrong direction & space all around the position of the petcock itself does not allow that.

Thanks to the owners who made me aware of this upgrade.......priceless info & what an owners site is all about !!

Why update the petcock from the original anyway ???......a good question.

The original petcock only works with gravity meaning if you leave it in the ON or RES position it is constantly feeding the carbs. Also due to its basic design, it relies on just one little o ring to stop the flow of fuel even in the OFF position, and unfortunatley this very often fails. So yo thinks its OFF.....and its not.

The float jets on the 1300 carbs are not the best either & often allow fuel to pass when they should not (bowls full). This is not so much of a problem when running, but when not running you risk the carbs flooding. On most bikes this would just mean the fuel would flow out of the overflows & onto the ground below the bike........but NOT on a 1300 as it does NOT have carb overflows. This means the fuel goes straight thru the carbs & into the combustion chambers. It then runs past your piston rings & over time (overnight) completely fills your engine & gearbox with fuel.
This cannot happen on FUEL INJ models as they dont have carbs & the fuel pump acts as a stopper as well.

YOU CAN IMAGINE THE PROBLEMS THIS WILL CAUSE & THE COST OF MORE FRESH OIL & HAVING TO DISPOSE OF THE FUEL & OIL INSIDE YOUR ENGINE (but it does give it a real good clean inside!).

THE ANSWER !

Find & fit a petcock that is a VACUUM Type which can ONLY let fuel out when the engine is running. That way even if you leave the tap in the ON position you are much safer.....and when you get to my age, I am forgetting things more & more !!

I dont want or mean to cause unecessary worry here, but this is a long standing & common problem with the 1300.

Pete F

Not to say that a single vacuum line could not be the problem; but I have had many Kawasaki's with a single vacuum line to the carbs and have never had an issue with the intake pulse, causing low fuel flow.

I would suspect a blocked Tap, weak spring, defective diaphragm membrane (Most likely culprit) with a blocked tank drain or hose being 2nd.

If low fuel flow was attributed to a pulsing cylinder, I would suspect weak induction, i.e. vacuum leak or low compression, or improper valve timing/ adjustment.

Or something migrating down to one of the float valves, before I suspect a single vacuum line as being the culprit.

Knowing that our OEM fuel supply (Electric shutoff valve and overpriced) is a bit quirky, going from our old system to the ZX style is a much better, cheaper, and more reliable system.

Another factor in all of this is Ethanol. No rubber or neoprene parts made in the 80's and 90's was ever formulated to withstand our current crappy blend of fuel. (If we can even call it fuel)

Another consideration is a blocked tank vent. This can cause low fuel flow and I have run into this (sometimes) hard to diagnose problem. My Z1R kept running out of fuel at hwy speeds. I finally looked at the vent system and found the cap gasket was blocking the vent. Once it was installed properly, voila, power on demand.

Regards.

Todd.