Petcock Problems

the petcock on my kz550 ltd is acting up. my bike will run for a short time then die, and will not start back up until i set the petcock to prime again. i tried disconnecting the line that goes to the carbs and see if any fuel would come out with the vacuum line still attached and starting the bike on fluid. not sure if that is an effective method of testing it but no fuel came out so assume the petcock is bad. the PO did mention having problems with it previously, so the question is repair or replace? if repair, i am clueless on how to do so, and if not i know there are few different petcocks to chose from, and im not sure which is best. input would be greatly appreciated, thanks.

If you take the tank off, you can suck on the vacuum line and it should open the petcock in the "ON" position. That's only a vac line, gas shouldn't be going through there unless your diaphragm is tore up. I'm still not sure if gas would flow through there even with a bad diaphragm. I didn't test that.

Anyway, ever since I did a rebuild on my petcock, it would leak fuel in the "ON" position. I read that was a common problem with the rebuild kits for some reason. I ended up getting a heavier spring to keep it closed and just run it in the "PRIME" position. Just make sure to turn the petcock back to "ON" which is essentially off now. Just a temporary fix until I get a new petcock.

Running it on Prime won't hurt anything. As far as I know, the vacuum operated petcocks are just for safety. If your bike goes down and the engine shuts off, no more vacuum, the fuel stops flowing. If you go down with it on prime, the fuel will keep flowing out if it can. Also, if you rig your bike like mine, you'll lose the fuel reserve. It will run until it's empty.

i was not looking to see of fuel was coming out of the vacuum line, i wanted to see if anything was coming out where the main fuel line connects like it should. i left the vacuum line connected properly and started the engine, nothing came out of where the fuel line would be. what did the rebuild kit run you?

The purpose of the vacuum line that runs from the petcock to the carbs is to open the petcock when the engine is running. When the engine is running, vacuum from the carbs pulls on the diaphragm inside the petcock which in turn permits fuel to flow. So when you shut off the engine, or in your case when you disconnected the vacuum line from the carbs, no fuel will flow - this is normal. Ed

i must just be bad at explaining this, i never disconnected the vacuum line, just the fuel line, and then started the engine with fluid. the vacuum from the engine did not open the diagram when it started because no fuel came out of the petcock where the fuel line normally is. i also tried sucking on the vacuum line when attached to the petcock and no fuel flowed then either. im pretty sure the petcock is bad and i am taking it apart today.

can i just run it on prime all the time and turn it back "on" when im done? will this cause problems?

Be careful taking it apart , it may just be lacquered up from old gas and you could screw up the Diaphragm .

Do you have a shop manual ?

If not there appears to be one on file for your year.
kzrider.com/filebase/cat_view/102-1982/178-kawasaki-kz-550-a3

JD

dan123 wrote: can i just run it on prime all the time and turn it back "on" when im done? will this cause problems?

Sure. You can do that. ... run on Prime and switch off prime when stopped. Just like the older (and some of the newer) style manual petcocks. No problem

sweet thanks guys