Disable the vacuum on the petcock?

Somewhere out on the interweb lies a write up that shows how to disable the vacuum system on a petcock. Seems to me like it was just a simple on, res, and off after doing the modification. The trick was to tap one of the ports inside and use a set screw to seal it off (I'm sure it was more than just that). Does anyone else remember seeing something like this. I just stumbled on to it from searching for something else. Now I can't find it anywhere. Anyone have a link or experience with doing this? :whistle:

I used Seal-All glue, just figure out which passage to block by blowing through it, then moving the lever and blowing through it again.
There's no RES after this, either, just OFF and ON (PRI becomes ON).

Losing the reserve would rob a lot of gas. Not such a great mod then.

AtLarge wrote: Losing the reserve would rob a lot of gas. Not such a great mod then.

:laugh: Take the screen / stand pipe out, run a decent inline filter.

When the lever is positioned to PRIME, doesn't that bypass the vacuum system? :whistle:

Yes, it does. Just as putting a rubber cap on the carb nipple disables the vacuum system. No need to fool with the petcock itself, btw.
Unless Kawasaki petcocks are different from Suzuki petcocks, switching to PRI also uses the RES input feed line, not the ON feed line, so you will use all the fuel in your tank (whether by leaking because you left it on PRI too long, or you ran out of fuel).

guitargeek wrote:

AtLarge wrote: Losing the reserve would rob a lot of gas. Not such a great mod then.

:laugh: Take the screen / stand pipe out, run a decent inline filter.

Ah... that's a good idea. But then you would lose the low fuel warning. :S I do use a stone filter and watch my tripodometer so still something to consider...

daveo wrote: When the lever is positioned to PRIME, doesn't that bypass the vacuum system? :whistle:

True but, I want to get rid of the vacuum while being able to absolutely stop the gas from going through. Oh, and I don't want to pay for it. And I still wanted to retain the stock look. :lol: Now that's not asking too much is it? :laugh:

I appreciate the help guys. Right now I have the tank off after tweaking the stock unit AGAIN. Got it to seal well enough for one drop passing through every 12 hours. So, it's better but not perfect. I also adjusted my floats up a notch. I might just see if this gets me by. If not I'll either mod or go aftermarket.

That's why I did it, I was sick of having to change my oil because of gas in my crankcase! (Also, I couldn't afford a Pingel.) I had put in a second inline petcock, but it was hard to reach and sometimes I'd forget to shut it off. Out of sight, out of mind. I'd come out to start my bike and the garage would reek of gas. Sniff the oil cap and sure enough...

I still use that second petcock, too. Belt + suspenders, and it works as a theft deterrent, I guess?

Disassemble the petcock to see if you can figure out how to convert it to a manual fuel valve - it shouldn't take too much effort. One way would be to remove the diaphragm spring & install an in-line on/off fuel valve (such as for lawnmowers), but there will be no reserve.

On my 81 650-CSR the petcock can be converted by installing the tap lever & tap lever cover 180^o from the normal position, but this way the end of the lever has to be cut off a little to avoid contacting the tank. There will be ON, PRI/RES, & OFF. Prime & Reserve would be the same thing, either way uses the RES fuel pickup
(81 KZ650-CSR petcock converted: ON = lever pointing up, PRI/RES = lever pointing right, OFF = lever pointing left).

New Kawasaki parts. A genuine oem diaphragm assy is only about $12 at places like RonAyers.com.
The rubber fuel tap gasket is less than 3 bucks.

K&L. I like having the vacuum actuated device. Mine was in good condition, so I rebuilt it w K&L parts
from Z1Enterprises.com - K&L stuff is made in Japan & oem quality (imho)(some aftermarket kits are junk, probably because they are not made in Japan). I expect to install a new diaphragm kit every 2-3 years.... no big deal or expense... it's a wear item - the thing gets flexed every time you start & stop the engine, so of course it will eventually fail.

Rebuilding. Disassemble & clean the petcock. Inspect it to see if it's worn or corroded or something.
If it's in good condition, you should be able to rebuild it w new rubber parts - you may only need a diaphragm kit.
If you decide to rebuild it, buff the surfaces w steel wool or brass wool, especially where the diaphragm o-ring contacts the petcock body - that orifice needs to be polished smooth so that the o-ring forms a good seal.

Manual fuel valve.
If the bolt hole spacing is 34mm, here's a topic w some options: KZR topic - Manual fuel valve option