Where does the petcock line connect

Ok I have had my bike apart more time than I can count. had a buddy do my carbs when I first got it he had his son pull em off and put em on etc...

My vacum petcock has never worked on the bike but I just put it on prime and ride shut it off when
I stop. someoone posted a pic of carbs and where my vacum line is connected to the carb it says
vent in his diagram the other side has a vacum cap on it (I am convinced thats the way it was
when I got it)

does the vacum connect the intake boot?? I can feel a little (minor) vacum when i put my finger
over it and it runs great. if those are supposed to be vents. I never think about it when
I am around my bike to check and see.

I have manually tested the petcock and it worked off the bike. and are the 2 brass fittings comming out of the carbs for vents??

oh yeah 78 KZ1000 A2A

here is a pic of the other side with a vacum cap on it

Courtesy of wiredgeorge:


If the carbs have a dedicated vacuum nipple (as indicated by the green line), use a vacuum hose from it to the petcock.

If the carbs don't have a dedicated vacuum nipple (as indicated by the green line), use a vacuum hose from the vacuum nipple on any carb holder to the petcock.

The carb holder nipples aren't shown in the pic.

Any unused vacuum nipple, wherever located, should be capped/plugged.

If there's a dedicated vacuum nipple (as indicated by the green line) that's failing for whatever reason to supply sufficient vacuum to the petcock, would cap/plug it, and use one of the carb holder nipples as vacuum source for the petcock.

Good Fortune!

Thanks Patton mine are a little different than the pic but ever since you posted this in another thread it has borhered me. If the 2 outer nipples are vents on the non pumper carbs then That is a problem I need to address and the scource of my petcock not functioning properly

On similar carbs for 1976 KZ900 LTD, with a manual petcock, each of the two vent hoses connects to it's own vent nipple, and the pair of vent hoses is routed to exit underneath the seat (attached to clips molded into the top of the air box cover), which is the oem fitment.

Some owners opt to route the two hoses where they exit underneath the bike instead of underneath the seat.







Good Fortune!

That looks exactly like my set up. I hate not having my bike here to run out and look.

I cant blame the kid for hooking it back up they way it came apart I have been doing
the same thing but I definately need to let him know as he has my buddies at his shop
doing the carbs as we speek lol

gives me a reason to go to town and ride again tomorrow

The basics for carb hose connections:



Vent hoses must always exit to open air, regardless of petcock design.

All unused vacuum nipples must be capped/plugged.
This usually includes the vacuum nipple on each carb holder.
And would also include any extra vacuum nipple that might exist for a vacuum petcock that's been replaced with a manual petcock.

A vacuum petcock is supposed to always allow flow fuel in the PRI position, but requires vacuum for fuel flow in the ON position and in the RES position.

A manual petcock of course doesn't need any vacuum.

Good Fortune!

Yeah, the carbs on the A2A are a little different.
You have 3 vacuum and 2 fuel pipes.
The middle vacuum hooks up to the top fitting on the inside of the vacuum petcock .

There is a diaphragm in the petcock and when it receives minus pressure it opens the flood gates.
( I like these clear fuel lines I'm using now , very easy to see whats going on)

Unfortunately I don't think there is a rebuild kit available any more, so if you investigate be careful or you may end up buying an after market petcock.

I suggest you take the caps off the outer vacuum pipes and install the tubing as Patton suggests and run them under the seat, letting them hang could be a bad thing if you are caught riding in the rain or go through a puddle.

One more thing, the tubing for the vacuum pipes is one size smaller than the 1/4" stuff I'm using for the fuel line but the local auto parts store had something that worked ok not metric though.
The middle one has to be a tight fit for the petcock to work.


JD

bluej58 wrote: Yeah, the carbs on the A2A are a little different.
You have 3 vacuum and 2 fuel pipes.
The middle vacuum hooks up to the top fitting on the inside of the vacuum petcock .

There is a diaphragm in the petcock and when it receives minus pressure it opens the flood gates.
( I like these clear fuel lines I'm using now , very easy to see whats going on)

Unfortunately I don't think there is a rebuild kit available any more, so if you investigate be careful or you may end up buying an after market petcock.

I suggest you take the caps off the outer vacuum pipes and install the tubing as Patton suggests and run them under the seat, letting them hang could be a bad thing if you are caught riding in the rain or go through a puddle.

One more thing, the tubing for the vacuum pipes is one size smaller than the 1/4" stuff I'm using for the fuel line but the local auto parts store had something that worked ok not metric though.
The middle one has to be a tight fit for the petcock to work.


JD

When I painted my tank I tested the pet cocock and It worked (sucking on the vacum line NO Jokes Please LOL) but when we fired the bike up it ran and acted like it was running out of gas with the petcock on ON or RES so I just road with it on prim. It was bothering me ever since I saw the pic's showing vents

I'm at the point now I have put about 300 miles on it I can start fixing the annoying things.
got caught in a torential down pour yesterday and was impressed with no run problems the pods were litterally dripping with water.

Thanks guys!!

The two vent nipples are not to be confused with the four vacuum nipples on the carb holders, which vac nipples are supposed to be capped during normal running.

Some carbs have a 5th vac nipple located on the air box side of the carb.
When present, such 5th vac nipple is intended to supply vacuum through a hose to a vacuum petcock.
If such 5th vacuum nipple is present, but not needed for a vacuum petcock, such 5th vacuum nipple should also be capped.




Good Fortune!

perfect thanks!!!

Patton wrote: Courtesy of wiredgeorge:

I know these carbs are different than on the A2A, but it shows three nipples drilled in the same location on the 2, 3 and 4 carburetors , same as on the A2A's

I guess my confusion is the fact that the middle one on the # 3 carb is definitely a vacuum even though they all look the same.

I read something a while back that I can't seem to find right now, but one thing I remember it saying was not to plug the 2 and 4 carb nipples like you did in that pic Ramtough,they need to be open.

I'll keep looking.

JD

bluej58 wrote:

Patton wrote: Courtesy of wiredgeorge:

I know these carbs are different than on the A2A, but it shows three nipples drilled in the same location on the 2, 3 and 4 carburetors , same as on the A2A's

I guess my confusion is the fact that the middle one on the # 3 carb is definitely a vacuum even though they all look the same.

I read something a while back that I can't seem to find right now, but one thing I remember it saying was not to plug the 2 and 4 carb nipples like you did in that pic Ramtough,they need to be open.

I'll keep looking.

JD

Thanks i am gonna try to sort this out tomorrow when i go get my bike. My Carb guy did it that way when he did my carbs (well...his son did) the thing runs great i am just wondering if there will be a performance gain when I unplug the vents? or what if any benefit the vents are. I really need to read up on it if I can find any info on it any tech info would be greatly appreciated.