Petcock Scenario

[BeerMonger]

I'm working on a 1982 GS850G.
I took the tank off yesterday and when I turned the petcock to PRI to drain it, nothing came out. So I applied a vacuum to the line and voila, it starts draining. The petcock doesn't need vacuum to allow free flow in the PRI position does it? Isn't that the whole point of prime?
Both ON and RES settings also required vacuum present (as suspected).

Now the question: Should I just turf this petcock and order from Z1, or try a rebuild kit? It's about $20 for rebuild versus $45 for new.

[Ghostgs1]

Hi BeerMonger,

Not sure but I think there were some that did not really have a prime position, but I may be dreaming that. I don't know if it is possible to assemble it to produce the results you have seen, but it sure sounds like it may be. I'd take it apart and look at the flow paths to determine what is happening. If it allows flow when you have vacuum and shuts it off when it should, I think it is good. Maybe install new seals and diaphragm if they are questionable. Don't think there is anything in there that can wear except the rubber goods. Ray

I'm working on a 1982 GS850G.
I took the tank off yesterday and when I turned the petcock to PRI to drain it, nothing came out. So I applied a vacuum to the line and voila, it starts draining. The petcock doesn't need vacuum to allow free flow in the PRI position does it? Isn't that the whole point of prime?
Both ON and RES settings also required vacuum present (as suspected).

Now the question: Should I just turf this petcock and order from Z1, or try a rebuild kit? It's about $20 for rebuild versus $45 for new.

[spyug]

I find rebuild kits to be a PITA and usually the petcock goes wonky again in short order. There are 2 vacuum petcocks on the XS and they are notorious for crapping out. I rebuilt them both twice and gave up going instead to a single manual type. Works much better but you need to remember to turn it off after the ride.

I'd opt for a new petcock to be safe.

Cheers,
spyug

[tas850g]

i think most people here go with a new petcock. Rebuilds are not worth the time and money spent on them as they either do not work or they soon fail again.

[rphillips]

Some of the GS petcocks need some vacuum to get the flow started, while in the pir position, but when it starts, it will keep flowing wothout vacuum. Not sure about an "82" 850. NNew or rebuild, seems about 50/50, personally I vote for a kit first. Just my opinion.

[teet]

I'm working on a 1982 GS850G.
I took the tank off yesterday and when I turned the petcock to PRI to drain it, nothing came out. So I applied a vacuum to the line and voila, it starts draining. The petcock doesn't need vacuum to allow free flow in the PRI position does it? Isn't that the whole point of prime?
Both ON and RES settings also required vacuum present (as suspected).

Now the question: Should I just turf this petcock and order from Z1, or try a rebuild kit? It's about $20 for rebuild versus $45 for new.

I'm a believer in buying a new one at that price. It's not worth it to me to spend the money on a rebuild, to have it possibly still not work. I would rather get a new one for a little more. I just picked one up for my 79 gs1000 from Z1, and it fits, and works excellent! The one I picked up was $41...

Also....I had the "dreaded" 80 petcock before with the screwdriver slot, and it seemed to be in the prime position all the time, as my crankcase had quite a bit of gas in it..after replacing it, no more gas in the crank case. Best $41 spent on my bike so far..


good luck

Jeff (teet)

[Disco Dan]

Took mine to bits not long ago.. tried to 'fix it'

Very easy to put back together wrong if it's a nice afternoon and the beer is flowing.

I suggest buying a new one.

There is a very tiny and thin bit of bent steel inside at a right angle that when the tap is turned to prime is meant to push against the membrane valve - normally opens with being 'sucked' open by vacuum hose on other side. If thats bent or broken Prime wont work. If your membrane is broken your on prime wether you like it or not.

[GSJim69]

I had a similar situation on my '82 850G. When I turned it to prime no fuel came. I didn't try applying vacuum. I suspected that the FN PO had tried to rebuilt it and messed it up like everything else.
I went with a new OEM, so I wouldn't have to worry about it as long as I have the bike.