kawasaki gt 550 only runs on prime.

[WULFSTAN]

Aright like the title says really bike will only run on prime anyone any ideas thanks.
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Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England

[RhynoCZ]

How's the tank breather and do you use fuel filter? If you use an fuel filter, then toss it away, there shall be none.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[WULFSTAN]

tank breather is fine and no fuel filter to speak of.
____________________
Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England

[RhynoCZ]

If the vacuum hose works, then I'd suspect the fuel tap itself or float valves in carburetors.

EDIT: I had the same problem, I found out the ''pipe'' where the float valve goes was grinded on 1st and 3rd carburetor, that caused the float valve to stuck because of vibrations. PRI just pushed hard enough on the valve and ''made'' it to go down again. The bike worked alright and then randomly died, like when you run out of fuel, no matter how far I got on it.
This thing:
https://i.ebayimg.com/t/Carb-Float-Valve-Kawasaki-Z250-Twin-1978-83-Motorcycle-/00/$(KGrHqN,!hsE3,H)57rtBN-OF5sToQ~~0_35.JPG
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[WULFSTAN]

Is running the bike on prime going to cause any problems?
____________________
Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England

[RhynoCZ]

No harm is going to be done, just don't forget to set it back on ON when you turn off the engine, to park it. Some dirt can cause the float valve blockage and the whole tank could drain into your engine. I did 5000km on PRI.

EDIT: ON means OFF when the engine is not running, that's why you should always put it on ON to prevent what I've mentioned.
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'87 Honda XBR 500, '96 Kawasaki ZX7R P1, '90 Honda CB-1, '88 Kawasaki GPz550, MZ 150 ETZ
'95 Mercedes-Benz w202 C200 CGI, '98 Mercedes-Benz w210 E200 Kompressor

[WULFSTAN]

[misscrabstick]

A Vacuum tap needs vacuum to open the fuel flow when the engine runs, a small pipe from the tap goes to the front of a carb so that the engine can suck on it, assuming the pipe is attached you probably need a rebuild kit for your tap as the vacuum diaphragm may well be split, this diaphragm opens the tap when engine vacuum pulls on it, if it is split then the vacuum is lost and the tap will not open.

[P.addy]

[prawny1]

provided the float valves are in good order and are the Viton/rubber tipped ones you will be fine running on prime,

problems come if your floats don't seal or are the metal tipped ones as those seem to always pass a little fuel even when new which will dilute your oil or hydraulic lock the engine when parked up especially if you park on the side stand.
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hellkat wrote:

Some people are only alive cos its against the law to kill them.

[WULFSTAN]

Thanks guys and girls ordered a fuel tap repair kit off wemoto lets see if that sorts it.
____________________
Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England

[WULFSTAN]

So i did try rebuilding my fuel tap now fuel comes out on res on and prime i put everything back in the way it came out any ideas why its pissing out when it shouldn't.
____________________
Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England

[map]

[hmmmnz]

i think your not getting any vacuum from the carbs,
the little pulse from the bike running allows the tap to let fuel through,
check that the small hose from the carbs to tap isnt blocked or doesnt have any splits or leaks
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the humans are dead
I kick arse for the lord
Wiring Diagrams BIDNIP it bitches

[WULFSTAN]

[map]

[WULFSTAN]

Yes i thought the tap myself so i bought a second hand one off ebay does the same thing but at a much slower rate. Could i have two fucked taps.
____________________
Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England

[misscrabstick]

Assuming the engine is off and therefore no vacuum to the tap, fuel should run through the tap in the PRIME position only, check your work again, you have fucked something up.

[map]

[WULFSTAN]

Sorted kind of no longer leaking while on. But now while the bike is running its leaking from the back of the tap will have a look again tomorrow.
____________________
Your backside is better enough for you to run again, if need be – bristle up the courage of the cornered rat, put on a bold front, and to hell with them. Bluff my boy – bluff, shift and lie for the sake of your neck and the honour of Old England

[lucidityofone]

sorry to hijack thread but does the smaller hose have to be a vacuum type hose or can you use fuel type hose instead?

Also on the right hand side of the bike, there is a black / grey circle box underneath the tank with an 8mm hose inlet coming out of it. Mine has nothing connected....what could this be?

Thanks.

[Casper]

Thinner fuel hose is fine for your vacuum one. The round thing you talk of will be the base of the fuel sender unit. You are just looking at the plastic cover and overflow hose. I have the same but lost the hose years ago.

[lucidityofone]

[Casper]

You trying to get an old bike back on the road again. Its all guesswork until you get those carbs out and cleaned on the inside. Sounds like your main jets are blocked or part blocked. Process of illumination and do the cheap stuff first. Not sure if UK got them but some early GT's had slode carbs. What are yours? If you have flat tops you have the vacuum ones what are almost the same as mine and easy to work on. Not the video I used but almost the same on how to strip your carbs

https://www.youtube.com/watch?v=95nlrP-yn2I

[lucidityofone]

yeah vacuum carbs. Ill rip them off and give them a good clean.

When idling it almost sounds like there is an air sucking noise near the tap.