Vacuum to Manual Petcock Conversion?

Hi KZR,

I need to rebuild my petcock since it is leaking fuel like a SOB and has contaminated my oil. While in there I was thinking hard about trying to convert this from a vacuum operated one to a manual. Did a search and found some posts about it but none really to my liking that fully explained what I was looking at. Came across a neat article via a Google power search that listed exactly how to do it on my bike.

" The GPz 750 and other bikes have "vacuum" operated fuel petcocks. When the motor is running vacuum keeps the petcock plunger in the open position so fuel can flow to the carburetors. In about 5 years time, the plunger (may) become stuck in the open position, thereby never shutting off the fuel. For people like me that trailer their bikes a lot, the fuel will fill the motor if left to the on state, as the bouncing of the fuel floats while trailering will let the fuel pass through the float valve needle flooding and overflowing the carbs. To fix this problem I first disconnected and plugged the vacuum connections to the petcock. I then removed the back side of the petcock housing that contained the plunger and plunger spring. I cleaned and lubricated the plunger and housing with WD-40. I took the spring and stretched it to twice its normal length and reinstalled. Now I manually work the petcock by leaving it in the "prime" position during running or the "on" or "reserve" position that is actually off now. This way I can run the majority of the fuel out of the carbs when I so desire. This is one system I can (and will) do without. The earlier heads also had smaller diameter exhaust pipe mounting studs than the later models. Be aware that putting in hot aftermarket cams can (might) affect the signals sent to CV carbs and make tuning them very hard. "

Full article can be found here: members.tripod.com/gpz_rider/technical/FAQ2000.htm

Can anyone verify this or has done it themselves? I really like that I am not gluing something, or bolting something off etc, it seems that it is merely stretching out the spring and then replacing the diaphragm/rubbers since those are chewed up thanks to the ethanol in the gas. This also seems like a much easier and faster way to convert than any of the other methods I have seen or read.

Thanks,

Running it on prime means no reserve.
Steve

swest wrote: Running it on prime means no reserve.
Steve

Understood and aware of that, but would rather do this than have to rebuild the petcock every single riding season since the ethanol in the gas out here destroys it within less than 12 months. Already happened a few times on at least one of the bikes that Pops rides as do I on occasion. Plus I am tired of my oil being contaminated and the bike/garage reeking of fuel every time it is parked for more than a day or two, this seems the lesser of the two evils to me.

Thanks,
Brett

There might be an inexpensive manual fuel valve that could be used.
If the bolt hole spacing is 34 mm, here's a topic: KZRider --- Manual fuel valve option
note: the spacing of the first fuel valve in the link might be 44mm. not sure.

martin_csr wrote: There might be an inexpensive manual fuel valve that could be used.
If the bolt hole spacing is 34 mm, here's a topic: KZRider --- Manual fuel valve option

Thanks Martin I will look into that If the bolt hole spacing is 34mm then would the Councorse conversion kit posted near the end of the thread also fit? I like how that is setup hence my question.

Thanks,
Brett

I don't know what the Concours kit fits --- you'll have to compare your petcock to the concours. I know there's something different from the 650-csr petcock, but I don't recall what. A replacement fuel valve would be cheaper than that kit. If yours is 44mm, there's probably a manual fuel valve in that size as well.

If ethanol deteriorating the rubber parts is really the problem, then stretching the spring and removing the vacuum line will not solve the problem because all those rubber parts will still be in there getting dissolved and will eventually leak.
All stretching the spring will do is smash the little o-ring more firmly against the valvevbody. Once it deteriorates, fuel will leak past it, and you'll be back where you started.

I use my reserve quite often. Wouldn't be without it.
Steve

If the bolt spacing is the same as the ZRX, Kwick makes a pretty sexy alternative.

kwickstand.net/Hyper-Formance.com/Lightest_Petcock.html

Thanks Texas, Martin and Steve appreciate the ideas and input. To address a few points let me say this... I know that regardless of whether I switch to manual or vacuum some of the petcock parts will have to be replaced yearly most likely due to the ethanol in the gas turning the rubber into sticky yet somehow hardened gum. That happens regardless, BUT what happens after that depends on what kind of petcock I am running. If it's a vacuum one I'm boned, it will flood the carbs, contaminate the oil and make me and the bike and the garage reek of gas (ask me how I know ) which is amazingly unpleasant. If however I use a manual one none of that happens. Sure I still have to replace the rubber each year but at least I avoid the contamination and flooding and smell. Yes there is a downside and just like most everything in life there are pros and cons to each with the big con on the manual being loss of reserve, but that's something I'm ok to deal with because that is a lesser evil for me (ymmv but this is my mileage) over the flooding and contamination and smell. Like most things this is about balancing the good and the bad and on my personal scale things balance out better with a manual petcock.

Appreciate all the feedback and ideas and I'm certainly not trying to poo-poo on anyone's preferences or POV, this is simply the direction I'm choosing to go.

Will try to get Pops to measure the spacing on my petcock as well as his 79' SR650 to help use as cross reference as well today. Going to hit the Kawi dealer this afternoon anyways and will see if I can confirm the bolt hole spacing on a ZRX1100/1200 too if I can. Don't know anyone with one near me so can't check in person sadly.

Thanks,
Brett

No eBay APP ID and/or Cert ID defined in Kunena configurationMaybe you can keep your reserve and use this. Thinking on a fuel cell in my top box.
Steve

No eBay APP ID and/or Cert ID defined in Kunena configuration

swest wrote: Maybe you can keep your reserve and use this. Thinking on a fuel cell in my top box.
Steve

Im going to be looking at several options for sure, and that is something I have considered. I am waiting to hear back from Pops on the bolt hole spacing on both my bike and his. Then when I am off work today (took the afternoon off paid, WOOT!) I am going to head to my local Kawi dealer and talk to the parts guy there and see if with his help I can't figure out the bolt hold spacing on the ZRX's and the Concourse 1000.

I suspect (still chewing on it and waiting to make a final decision) that I will just stretch the spring and replace the rubber on my current petcock on the old tank. Then when I have a bit of time while I refurbish the replacement tank I will have the answers and research I need to put in place a permanent solution when I swap the replacement tank over in a month or so. That way I can either order a kit, different petcock, in line shut off valve.... whatever I decide. I would like to make it trick but also clean and good looking.

Thanks, Brett