1996 Virago 750 Vacuum Lines (New Jersey)

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lunawoodworking
Posts: 18
Joined: Sun Oct 24, 2021 10:53 am
Location: New Jersey
What Virago you Own: 1996 Virago 750

1996 Virago 750 Vacuum Lines (New Jersey)

Post by lunawoodworking » Sun Dec 19, 2021 4:34 pm

Ok - I have a question... I have removed my carbs and am preparing to rebuild them. I am going to replace the fuel lines and was going to replace the vacuum lines (# 16 & 19 if you look at a Yamaha parts explosion of the intake).

This is a rubber hose with some sort of cannister in the middle of it. I noticed this part is used on marine engines as well. Anyone know what this is? One way valve (check valve), filter of some sort? I ask as it may be easier to just make one than trying to buy one - depending on what that thing is in line, and if that is available as a replaceable piece.

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ViragoJoe
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Re: 1996 Virago 750 Vacuum Lines (New Jersey)

Post by ViragoJoe » Sun Dec 19, 2021 5:26 pm

lunawoodworking wrote:
Sun Dec 19, 2021 4:34 pm
Ok - I have a question... I have removed my carbs and am preparing to rebuild them. I am going to replace the fuel lines and was going to replace the vacuum lines (# 16 & 19 if you look at a Yamaha parts explosion of the intake).

This is a rubber hose with some sort of cannister in the middle of it. I noticed this part is used on marine engines as well. Anyone know what this is? One way valve (check valve), filter of some sort? I ask as it may be easier to just make one than trying to buy one - depending on what that thing is in line, and if that is available as a replaceable piece.
Luna,
They're vent tube filters.

Click Images to Enlarge:
VENT CONNECTION CARBURETOR XV1100 1.png
VENT CONNECTION CARBURETOR XV1100 2.png


Carburetor Vent Tube:
"Those venting tubes coming out of the carbs near the top are important. They provide air to the main and pilot air jets, and maintain open air pressure throughout the carb body (except above the diaphragm). These tubes have little filter pods on them which contain two screens with a thin layer of foam sandwiched in between them. In many of them by now that foam has turned to dust. When you pull off your diaphragms and slides upon disassembly, look for dirt/dust coming in from those tubes. If there is some, you may want to deal with those filters, that is, provide the venting system with some fresh foam (UNI has some). I'll leave the details of this project up to you. Otherwise, just blow the filters out well with air and keep going. The main requirement is that they breath freely and are not shedding particles into your carbs..

The other important point about vent tubes is that they need to exit into quiet air to where wind and other sudden changes in air pressure don't find their way into the air jets. Older Virago's provide for this with outlets behind the left side cover, and newer ones with outlets in the pods."
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1996 XV1100SH Virago Special
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lunawoodworking
Posts: 18
Joined: Sun Oct 24, 2021 10:53 am
Location: New Jersey
What Virago you Own: 1996 Virago 750

Re: 1996 Virago 750 Vacuum Lines (New Jersey)

Post by lunawoodworking » Sat Jan 08, 2022 6:59 pm

I looked at those lines - not a bit of foam to be seen, but I can most certainly see a screen in each of the lines...

I did run in to another issue when taking the first carb apart - I am guessing that this is the first time the carb has been worked on, ever. To that end things are a bit, uh, stuck. The pilot jet is really jammed in there good, and I am afraid of shearing off the slot for the screwdriver, so I put a wire through it. However the seat for the needle valve was pretty much welded in - that rubber o-ring mechanically bonded the seat to the inside of the tube.

It took me quite a while to get it out - after mangling it a bit I ground a bolt to fit inside of it and then clamped a vise grip on it (the bolt was to keep the brass from collapsing), Then I got one of those crack smoking butane torch lighters and heated up the seat until I saw a bit of smoke (rubber burning), then I clamped the vise grips in the bench vise and had to pull with two hands on the carb to get it to finally break free (I also heated between pull attempts and soaked it with WD-40). I can do this again, but does anyone have any better suggestion? I was afraid I would have to put it in the mill and drill it out.

Also, any suggestions on that pilot jet? I am leery of putting too much heat on the aluminum - I am pretty certain it has been cleaned between the carb cleaner, the ultrasonic cleaner and the piece of wire - so I am ok with leaving it in place, but ideal would be to replace it as I have a new one in the rebuild kit.
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ViragoJoe
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Re: 1996 Virago 750 Vacuum Lines (New Jersey)

Post by ViragoJoe » Sat Jan 08, 2022 11:42 pm

lunawoodworking wrote:
Sat Jan 08, 2022 6:59 pm
I looked at those lines - not a bit of foam to be seen, but I can most certainly see a screen in each of the lines...

I did run in to another issue when taking the first carb apart - I am guessing that this is the first time the carb has been worked on, ever. To that end things are a bit, uh, stuck. The pilot jet is really jammed in there good, and I am afraid of shearing off the slot for the screwdriver, so I put a wire through it. However the seat for the needle valve was pretty much welded in - that rubber o-ring mechanically bonded the seat to the inside of the tube.

It took me quite a while to get it out - after mangling it a bit I ground a bolt to fit inside of it and then clamped a vise grip on it (the bolt was to keep the brass from collapsing), Then I got one of those crack smoking butane torch lighters and heated up the seat until I saw a bit of smoke (rubber burning), then I clamped the vise grips in the bench vise and had to pull with two hands on the carb to get it to finally break free (I also heated between pull attempts and soaked it with WD-40). I can do this again, but does anyone have any better suggestion? I was afraid I would have to put it in the mill and drill it out.

Also, any suggestions on that pilot jet? I am leery of putting too much heat on the aluminum - I am pretty certain it has been cleaned between the carb cleaner, the ultrasonic cleaner and the piece of wire - so I am ok with leaving it in place, but ideal would be to replace it as I have a new one in the rebuild kit.
luna,
The pilot jet is really jammed in there good, and I am afraid of shearing off the slot for the screwdriver, so I put a wire through it.
It should just unscrew and drop out without much trouble. I have no explanation for that. Same goes for the Needle Seat.

I can't see any other way to get that Needle Seat out than the way you explained you did it.

They are not usually that stubborn to remove. I have no idea why it needed that kind of muscle to be removed.

Was there a small screen filter on the end of the Needle Seat? There should have been one near the O-ring end. I'm not sure if the new replacement Needle Seat comes with it. If there wasn't one. That could mean the Needle Seat was replaced once before.

Not all rebuild kits show the screen on the Needle Seat like this one does.
Needle And Seat Assembly XV750 Mikuni.jpeg
I have no idea why these components have semi-welded themselves to the carburetor body.

Joe
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ViragoJoe 🇺🇸
1996 XV1100SH Virago Special
"Never ride faster than your Guardian Angel can fly!!"
;)


NOTE TO ALL:
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lunawoodworking
Posts: 18
Joined: Sun Oct 24, 2021 10:53 am
Location: New Jersey
What Virago you Own: 1996 Virago 750

Re: 1996 Virago 750 Vacuum Lines (New Jersey)

Post by lunawoodworking » Thu Jan 13, 2022 11:21 am

My guess is that these carbs had been gone through at least once in their life time (the bike has 38,000 miles on it). I came to this conclusion in part because both of those filter screens are gone, and one of the rubber boots between the carb and the cylinder head was missing the rubber o-ring - well, that and two of the bolts holding those boots on to the head were fairly well rounded and abused (I have procured new bolts).

The needle seat was just as stuck on the second carb, fortunately I went straight to fire and vice grips and got it out after about 10 minutes (went slow, didn't want to melt anything). I am guessing that whoever rebuilt or cleaned the carb last probably had some solvent left in the orifices when the components were re-installed and this slightly melted the rubber and when the solvents evaporated it 'welded' in place. I would also guess that this rebuild was well over a decade ago given how dirty things were.

I did think about boiling the carb to soften up the rubber, but because I could not remove that nylon piece that the slide rides in, I decided to forgo that procedure. I do have the security torx bits, and managed to get one of the screws out, then the second one was seized in there good, so I decided I had better leave well enough alone.

On the bright side, the ultrasonic cleaner machine works really well...

Well, now on to the next two projects - even though there are (supposedly) only 44 miles on this oil, I will be changing it - I am guessing with the carb problems I had that the oil is now full of gas. I have also procured some new steel braided brake lines (Spiegler) in an attempt to firm up the front brakes. Unfortunately the forecast is for 18 degrees here on Saturday - not sure my small heaters will be up to the task... could crank out the torpedo heater, but that whole gas and open flame thing kind of bothers me.
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