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Author Topic: How much vacuum?  (Read 7870 times)

Offline snarf

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How much vacuum?
« on: June 27, 2011, 11:09:07 AM »
How much vacuum is needed to open the petcock?  Currently on my '86 1-4 carbs are T'd together then leading up to the petcock.  It has 1/4" black fuel line on them.  I think this is way to sloppy.
Can carb #1 supply enough vac to open the petcock?  I have plenty of vac caps laying around for my block-off plates.
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline Vic Salisbury

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Re: How much vacuum?
« Reply #1 on: June 27, 2011, 11:32:13 AM »
It don't take much, normally, only #2 goes to the petcock. I think 1 & 4 for the reed valve contraption, #3 capped.

So I think pulling from #1 shouldn't be a problem as long as the hose cant be kinked.

1/4 is too big, but I dont know the proper vacumn hose size...
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Offline gtr1000

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Re: How much vacuum?
« Reply #2 on: June 27, 2011, 11:32:57 AM »
Quote from: snarf on June 27, 2011, 11:09:07 AM
Can carb #1 supply enough vac to open the petcock? 

I thought that was the way all C-10's were  :-\

Mod - Me wrong  :-[, #2 for vacuum
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Offline snarf

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Re: How much vacuum?
« Reply #3 on: June 27, 2011, 12:13:20 PM »
Quote from: gtr1000 on June 27, 2011, 11:32:57 AM
I thought that was the way all C-10's were  :-\

Mod - Me wrong  :-[, #2 for vacuum
Yeah I couldnt remember if it was 1 or 2.  The bike came with the 1/4" hose.  I never paid any attention to it until this weekend.  The vac caps that I include with my BO plates are 3/16".  Looks like it's time to get rid of all that unnecessary hose and hook #2 up to the petcock.
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline buzzcut

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Re: How much vacuum?
« Reply #4 on: June 27, 2011, 02:52:14 PM »
all I can sya is my '86 takes vacuum off #2 also.  Seems Ireplaced theline with 3/16 but don't quote me. 
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Offline Steve in Sunny Fla

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Re: How much vacuum?
« Reply #5 on: June 27, 2011, 02:58:32 PM »
Hey Chris - the T may be your problem. since 1-4 fire 360* opposite of each other, I think each time you're trying to pull a vacuum on one cylinder, you're just negating the vacuum pulse by supplying air from the other cylinder. Steve
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Offline kzz1king

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Re: How much vacuum?
« Reply #6 on: June 27, 2011, 03:18:37 PM »
 ;D You may have solved a problem for me Steve with my cruise. I have 1,3 and 4 with the more is better theory for my auduivox. I will try just pulling off of one cylinder or if I use 2 cylinders I suppose I would use 1 &3 or 2& 4? Hope that is the problem but I don't think it is vaccum related. Easy to check though.

Wayne
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Offline snarf

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Re: How much vacuum?
« Reply #7 on: June 27, 2011, 03:23:06 PM »
Quote from: Steve in Sunny Fla on June 27, 2011, 02:58:32 PM
Hey Chris - the T may be your problem. since 1-4 fire 360* opposite of each other, I think each time you're trying to pull a vacuum on one cylinder, you're just negating the vacuum pulse by supplying air from the other cylinder. Steve
More than likely I just fixed it.  Removed all the T's, capped 1,3,and 4.  I used to have to crank this bike over for ever to get it to start cold.  First hit of the button she came to life. 
I am getting ready to meet up with Tele130 on his journey through Iowa.  I will know soon enough.  Thanks everyone for the info.
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline snarf

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Re: How much vacuum?
« Reply #8 on: June 27, 2011, 03:41:32 PM »
I couldnt wait any longer to try the bike out.  I just went for  a short ride.............OH YEA!! She runs like a champ.  I dont know why it started doing this (a while ago)?? It has been like this since I rode her home from the Nationals.  I remember being extremely impressed with her on the way home.  Maybe I was just on a natural high ??? :o ::).
Well either way, NOW I can start to dial in the foam that I have stuffed in my air box.  Damn this is just like Christmas :chugbeer: :thumbs: :chugbeer: :thumbs: :chugbeer: :chugbeer: :thumbs: :chugbeer: :chugbeer: :chugbeer:
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline Steve in Sunny Fla

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Re: How much vacuum?
« Reply #9 on: June 28, 2011, 09:09:18 AM »
Now you know why long distance diagnosis is next to impossible. I had no idea that the vac line was tee'd all along while you were asking for diagnosis; If I had seen the bike in person I would have removed the Tee immediately.

  To those using multiple vacuum ports, you can source a one-way vacuum valve from automotive applications. I pull them from toyota trucks I've worked on, but you'll have to check with your local autoparts stores for applications. HTH, Steve
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Offline snarf

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Re: How much vacuum?
« Reply #10 on: June 28, 2011, 09:21:55 AM »
Quote from: Steve in Sunny Fla on June 28, 2011, 09:09:18 AM
Now you know why long distance diagnosis is next to impossible. I had no idea that the vac line was tee'd all along while you were asking for diagnosis; If I had seen the bike in person I would have removed the Tee immediately.

  To those using multiple vacuum ports, you can source a one-way vacuum valve from automotive applications. I pull them from toyota trucks I've worked on, but you'll have to check with your local autoparts stores for applications. HTH, Steve
:nuts: :nuts: Oh I know how aggravating it can be.  I have fought this for a while (compounded with water in the gas).  I do appreciate your help more than you know. 
Soooooo, what is a good starting point for the size of foam?  I have had so many different sizes in there I kinda forget what I started with.  PM me if ya wanna
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline connie_rider

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Re: How much vacuum?
« Reply #11 on: June 28, 2011, 10:11:51 AM »
Geez, Snarf.... REALLY GLAD YOU FIGURED IT OUT...!!

I recall your problems back some time ago.
Everybody was straining their brains trying to help you figure it out...
Like Steve sed, hard to troubleshoot from long distance...

I read one of your notes recently about a stumble at XXX RPM's... Did that stumble go away also?

Ride safe, Ted
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Offline snarf

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Re: How much vacuum?
« Reply #12 on: June 28, 2011, 10:34:10 AM »
Quote from: connie_rider on June 28, 2011, 10:11:51 AM
Geez, Snarf.... REALLY GLAD YOU FIGURED IT OUT...!!

I recall your problems back some time ago.
Everybody was straining their brains trying to help you figure it out...
Like Steve sed, hard to troubleshoot from long distance...

I read one of your notes recently about a stumble at XXX RPM's... Did that stumble go away also?

Ride safe, Ted
Yup cleared it right up. The way T-Cro explained it, plus the info SISF just gave; when I was rolling on the gas I was fighting for vac and the slides did not want to open. She purrs now.
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline connie_rider

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Re: How much vacuum?
« Reply #13 on: June 28, 2011, 10:37:34 AM »
Found the Post I was referring to.

How much of a vac leak would it take to bog our bikes down? My bike is bogging down at wot. Mainly between 4-5 k then it pulls out of it like a monster. I have always thought the vac lines were sloppy on the nipples. It idles and revs great, it just bogs under heavy accel.

Mucho easier to trouble shoot with the info about the lines being T'eed together.     
My guess: At WOT the vacuum drops. So your vacuum to the petcock (which was probably borderline at idle because of the "T") was not enough to keep the petcock open at WOT. Engine was starving for gas!
As the rpm's came up, the vacuum increased and the petcock opened back up.....

Heck you even said,,,, I have always thought the vac lines were sloppy on the nipples.   
None of us caught that the plural "Lines and nipples".   :o

It's all Steves fault!!!  He shoulda known!!  <evil grin>     :rotflmao:
Ride safe, Ted
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Offline snarf

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Re: How much vacuum?
« Reply #14 on: June 28, 2011, 10:45:17 AM »
Quote from: connie_rider on June 28, 2011, 10:37:34 AM
Found the Post I was referring to.

How much of a vac leak would it take to bog our bikes down? My bike is bogging down at wot. Mainly between 4-5 k then it pulls out of it like a monster. I have always thought the vac lines were sloppy on the nipples. It idles and revs great, it just bogs under heavy accel.

Mucho easier to trouble shoot with the info about the lines being T'eed together.     
My guess: At WOT the vacuum drops. So your vacuum to the petcock (which was probably borderline at idle because of the "T") was not enough to keep the petcock open at WOT. Engine was starving for gas!
As the rpm's came up, the vacuum increased and the petcock opened back up.....

Heck you even said,,,, I have always thought the vac lines were sloppy on the nipples.   
None of us caught that the plural "Lines and nipples".   :o

It's all Steves fault!!!  He shoulda known!!  <evil grin>     :rotflmao:
Ride safe, Ted
No kidding I guess I oughta buy a 7th gear bevel from him so he can afford a new magic eight ball.
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline snarf

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Re: How much vacuum?
« Reply #15 on: June 28, 2011, 10:48:26 AM »
Well SH!!!T.  A guy just cant catch a break.  I just fired the bike up to grab a bite to eat and I have fuel coming out of num three bowl (god bless overflow tubes).  I tried blowing air up from the bottom of the bowl but alas no love.  If I blow from the fuel inlet hose do you spose it would unstick the float enough to get me home?  :banghead: :banghead: :banghead:
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline connie_rider

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Re: How much vacuum?
« Reply #16 on: June 28, 2011, 10:53:12 AM »
Might help, but tapping on the side of the carb while idling might be more likely to knock a bit of trash loose.

Better yet would be to stop the flow of gas to the carbs and let the engine idle, While idling (and using fuel) the valve will open fully.
LIGHTLY,,,, Tap, tap, tap..... Mebbe the trash will fall out...

Ride safe, Ted
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Offline snarf

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Re: How much vacuum?
« Reply #17 on: June 28, 2011, 10:55:29 AM »
Quote from: connie_rider on June 28, 2011, 10:53:12 AM
Might help, but tapping on the side of the carb while idling might be more likely to knock a bit of trash loose.

Better yet would be to stop the flow of gas to the carbs and let the engine idle, While idling (and using fuel) the valve will open fully.
LIGHTLY,,,, Tap, tap, tap..... Mebbe the trash will fall out...

Ride safe, Ted
Worth a shot.  Thanks for the info.  I will know more around 4:30
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2002 Conc
1986 Conc "The spirit of COG"

"We did not become the men that we are because we were Sailors, soldiers or cops; we became Sailors, soldiers and cops because of the men we are."

Offline Steve in Sunny Fla

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Re: How much vacuum?
« Reply #18 on: June 28, 2011, 01:48:04 PM »
If you have compressed air, open all the bowl vents and blow down through the fuel line. a small piece of trash can hold the needle off the seat. BTDT. Steve
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Offline Steve in Sunny Fla

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Re: How much vacuum?
« Reply #19 on: June 28, 2011, 01:51:06 PM »
Quote from: snarf on June 28, 2011, 10:34:10 AM
Yup cleared it right up. The way T-Cro explained it, plus the info SISF just gave; when I was rolling on the gas I was fighting for vac and the slides did not want to open. She purrs now.

  No, what was happening is that the bowls were being starved for fuel. go back to a 1.75" piece of foam. Steve
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