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petcock nightmares

  • Thread starter Thread starter 94ta
  • Start date Start date
9

94ta

Guest
Im really getting sick of this bike and its personality. It took me to the edge today after I ended up getting about 4 tablespoons of gasoline straight into my eye.

Bought a brand new petcock but its the wrong size. The holes are to far apart to bolt it to the tank.

So then a petcock rebuild kit was purchased. It came, i put it in, nothing different. It is ALWAYS flowing fuel through the petcock. Its supposed to be vac operated and im under the impression that if you unhook the fuel lines, fuel shouldnt gush out from it. This is also a problem when the bike isnt running, and when it is good old #2 carb is dumping fuel. I spent 235$ on a newly used set of carbs on ebay. The ones i had had a few springs missing and needles and adjustment screw tips broken. The bike runs with the new carbs, it idles high even when i adjust it and when i rev it the revs just hang. it will take 5 seconds if you blip the throttle to 3000 for it to fall back down to 1400ish.

My only guess is the petcock is totally messed up or im missing something somewhere. the diaphram isnt ripped or anything, and to the best of my knowledge its assemebled correctly. The pet cock, then the plastic spacer peice, and then the diaphram, then the spring, then the cap with the vac line. thats the only way it will go together.

No matter what way i assemble it or what parts i use, it just wont stop fuel from flowing.

What do i do?

Thanks
 
Do you have it in the prime position? What bike? What petcock?

The hanging idle sounds like a vacuum leak and is probably not petcock related.
 
Yeah I would check to make sure it's not on prime like he said. If you read some posts on this site about petcocks I think you will find a lot of people only use oem. As a matter of fact, I just bought one today that is oem so I don't have the headaches you're talking about. Good luck!
 
Definetly the only reason it is always flowing is its in prime and not the on position which is with switch going up and down not to the left or rt. If # 2 is flooding out the vent line when its running, you got a carb issue. Most likely the "air mix" screw is not set correctly. The carb rebuild section fixed this problem for me. These bikes can be a pain! Dont go throwing money away before you do some extensive reading on this site. Trust me, i have plenty of holes in my walls from the frustration my 850 causes me. Damn bike still wont even start..
 
94ta said:
What do i do?
Click to expand...
One of the FIRST things you could do is give us a clue what bike we are discussing.
shrug2.gif


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Tatratbiker850 said:
If # 2 is flooding out the vent line when its running, you got a carb issue. Most likely the "air mix" screw is not set correctly.
Click to expand...
The 'air mix' screw as you call it, isn't even remotely connected to the reason fuel is coming out the vent line.
 
Your bike is an inanimate object. If things are right it will run right. You must take your time, be methodical and follow the checklist on BassCliff's site. Buying a petcock which does not fit is not the bike fault. The carbs you bought on ebay must be checked thoroughly - they may have all sorts of problems. There are no short cuts. Sorry but this is the only path to success.
 
Oops, cant beleive i forgot to tell you what bike, its a 1979 gs1000

Prime on and res all let fuel freely through the petcock.

The bike has the conical air filters, not a stock air box.

The thing im worried about is BOTH sets of carbs did this. It wasnt overflowing the vent line but the overflow nipples underneath the carbs. both sets of carbs did this.

I think the hanging revs are from the stock size jets and the conical air filters.

No matter what position the petcock is in it always flows fuel like theres nothing stoping it. With the petcock assembled i can blow straight through it in any position as well. The Aftermarket one that doesnt fit, this isnt the case. When I try to blow through it i cant.

Ive built a 94 trans am, cam, headers, valve train, stallconverter. Im not a mechanical idiot, this bike is just cursed haha. Im not throwing money at it just to do it. Right now the part in question is the fuel petcock. If i can blow through it and it flows gas through it in any position, then it cant be right...correct?
 
The petcock is knackered. Buy a new oem about $90. And it sounds like you have some sticky float valves. Take the bowls off the carbs and investigate.
 
OK, we know the year and the size, now how about the model?

It's not uncommon for the the carbs to overflow as long as there's gas free flowing to them with the engine off. States this on the caution on page 18 of the '79 GS1000/GS1000E owners manual (link below). Also, while you're on that page, is that the type of petcock you have?
It is possible that your carbs are OK, mine overflows if let in PRIME, so I try not to ever do that. So, now the main focus is that petcock.
http://www.mtsac.edu/~cliff/storage/gs/GS1000E_Owners_Manual_79.pdf
 
94ta said:
Oops, cant beleive i forgot to tell you what bike, its a 1979 gs1000

Prime on and res all let fuel freely through the petcock.

The bike has the conical air filters, not a stock air box.

The thing im worried about is BOTH sets of carbs did this. It wasnt overflowing the vent line but the overflow nipples underneath the carbs. both sets of carbs did this.

I think the hanging revs are from the stock size jets and the conical air filters.

No matter what position the petcock is in it always flows fuel like theres nothing stoping it. With the petcock assembled i can blow straight through it in any position as well. The Aftermarket one that doesnt fit, this isnt the case. When I try to blow through it i cant.

Ive built a 94 trans am, cam, headers, valve train, stallconverter. Im not a mechanical idiot, this bike is just cursed haha. Im not throwing money at it just to do it. Right now the part in question is the fuel petcock. If i can blow through it and it flows gas through it in any position, then it cant be right...correct?
Click to expand...
Next time you have it out, pull it apart in the order you have it, snap and post a pic.

I'm not sure you do have the petcock together properly. It could just be me, but your description makes it sound like the spring is not in the right place. On my 83 650G (admittedly a different petcock than the one on your '79), the spring sits between the metal barrel in the middle of the diaphragm and the plastic barrel of the petcock "switch". That way it opposes the action of the vacuum to close the diaphram when there is no vacuum applied.

I can post a pic of that for you tonight as I currently have no fuel in the tank as I sort out my own running issues.
 
BassCliff, yes thanks for reminding me of that post.

The petcock that has the mounting points too far away is measureing out to be in the 48-50mm range. The one i have/need is probably a 44mm.

I rearrange the way it was put together, I put the spring in the barrel.. Now when i blow through the vac line, i cant, but with the petcock installed on the tank and the lever in PRI/RES/ON fuel still flows out very very quickly in any position, nothing is restricting it in any position.

I was under the impression that with these vaccum style petcocks the carbs gets different amounts of fuel at idle then it would when revving. This is why i think the carbs are dumping fuel at idle. In the past with the petcock befor it was rebuilt it would dump fuel while idling and while not running. I dont want to make the house smell like gasoline another night but i dont think this "rebuild kit" cured anything and most likly wasted 40$.

The floats being stuck is a possibility, I havent taken these carbs apart yet since i was told they came off a running bike and didnt sit long at all, They probably do need a good cleaning, I dont really want to dive into that untill i get this petcock figured out.
 
So.......... before I go any further here, is that the same petcock as the one on page 18 of the owners manual in from the link in my previous post?
And what model GS1000 do you have?
 
Yes, the vacuum petcock with the 44mm (approx 1 3/4") bolt-spacing should work on your '79 GS1000.

NO - you shouldn't be able to blow thru a petcock that's not in the PRI position.

However - if fuel is dumping from #2, it's indicative of a float valve (needle & seat) failure.

Not returning to idle typically implies an air leak of sorts. Pod filters and stock jetting shouldn't influence this.

Don't get discouraged - eat that elephant one bite at a time.
 
There is a check valve inside the petcock for the vacuum line. You should be able to determine if it works by sucking and blowing air through it. All bets are off if you can blow air freely both ways.
I've had some success rebuilding these petcocks. You have to align the holes on the diaphram, to the hole in the block that fits between the two sides of the diaphram, to the breather hole on the main part of the petcock that goes to the front of the diaphram. I learned through trial and error, but the one thing I was overlooking because it's hard to see is that hole on the petcock, it's about in the 2 o'clock position as you look at the front of the petcock, close to the upper right hand mounting plate that attaches to the back plate, close to one of the 4 back plate mounting screws. If that hole is clogged your petcock will not breathe and allow your diaphram to open and close normally.
Also that 4 hole rubber seal under the selector lever has got to be good, as does the seat the little O ring mates to on the diaphram. Your vacuum line should be in about the 10 o'clock position as you look at the front of the petcock. Any little dirt can cause it to fail, I soaked mine in gasoline and put it together loosely, to allow the diaphram to find it's own center and tightened down the screws evenly.
The carbs flooding to me is normal if the bike sits and has gas going to the carbs. Both my bikes have done it when I left it in Prime, and it is clearly stated in the owners manual that can happen.

Also, there is an old post I have been trying to find that I have not been able to locate. It concerns a "modification" to the petcock that will not allow fuel to flow, but you can't forget to not turn it off. I didn't want to suggest that yet for fear of taking responsibility for it should that fail, so I'm still looking for that post.
 
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