Virago 700 in the shop

[Deleted member 69715]

Unfamiliar with those particular carbs but I think you need vacuum. There may be a spigot between the carbs and manifolds. You can use hose.
70% of stopping power is on the front brakes. Bike probably weighs 600 lbs or so, that twin caliper set-up will come in handy when some pencil neck pulls out in front of you.

 

[tghsmith]

there was a kit that used a virago as a doner,, from 20ft away it looked like a vincent..

 

[great white]

Apparently I am causing a lot of stir by not having any photos for you guys. Photos are on the agenda
for tomorrow morning. Maybe we can group think on this and give the bike a good name.
I was picking on it because there are so many things wrong that need repair or attention.

One thing I think I found about in regards to the starter slipping problem is that there is supposed
to be a washer (about 2.5 inches in diameter) in the starter that I think would sandwich in the
starter assembly that would keep the planetary gear in there from turning. I found the blow up photo
of the starter in the Haynes manual and it showed the big washer.

While I'm at it, I have a question concerning carburetors that have a diaphragm on the top
with the tapered pin that is connected to it and controlling the jet aperture. I'm wondering
what it is that makes the diaphragm and pin move when opening the throttle. The carbs
are 40mm Hitachi and when you open the throttle, the cylinder with the pin and diaphragm connected
do not move. Is it vacuum that moves the diaphragm assembly and if so do I need some
hoses to accomplish this or is it built internally into the carburetor? I did take it apart for
cleaning and everything seems to operate smoothly.

One thing I did notice sitting on the bike is that the front wheel seems to stick out significantly ahead
more than my usual ride which is a Yamaha XS 650.

On the weight balance subject: I wonder why there are double disc brakes on the front, seems counter intuitive
to me but I suppose the weight shifts forward on braking maybe.

Thank you all for your comments.

Cv carbs use pressure to lift the slide and needle, there's no mechanical connection between throttle cable and slide.

The venturi creates a low pressure zone. The passages in the carb duct this to above the diaphragm. There are also passages that duct atmospheric pressure below the diaphragm. The throttle cable opens the butterfly, which increases flow through the carb venturi. Then, the higher atmospheric pressure under the diaphragm lifts the carb slide and needle, allowing more fuel to enter the venturi and mix with the incoming air charge.

There's a lot more going on and that's a pretty simplified explanation, but it's how the slides/diaphragms work in a cv carb.

Perhaps a pic might make it a bit clearer:

 

[cathead]

Cv carbs use pressure to lift the slide and needle, there's no mechanical connection between throttle cable and slide.

The venturi creates a low pressure zone. The passages in the carb duct this to above the diaphragm. There are also passages that duct atmospheric pressure below the diaphragm. The throttle cable opens the butterfly, which increases flow through the carb venturi. Then, the higher atmospheric pressure under the diaphragm lifts the carb slide and needle, allowing more fuel to enter the venturi and mix with the incoming air charge.

There's a lot more going on and that's a pretty simplified explanation, but it's how the slides/diaphragms work in a cv carb.

Perhaps a pic might make it a bit clearer:

View attachment 434003

Thanks so much for taking the time to make the perfect explanation!

 

[great white]

dual front discs are more often than not an “appearance” thing. Especially on cruisers. They’re usually moving slow enough that a single disc is enough. Add that they’re a rear weight bias machine and a single disc is more than capable of locking up the front wheel.

Sportbikes (and really heavy bikes) benefit from the added braking power of a dual disc setup and the large the disc diameter, the more braking power they can provide.

I’d say cruisers with two front discs have them for mainly two reasons:

1. marketing. They don’t want the buyer looking at the bike and feeling like something is missing compared toa competitor
2. smaller discs. If putting dual disc on a bike that can do with one larger disc, they shrink the diameter of the disc for both braking “feel” and attempting to reduce production costs.

Really, whether single or dual brake discs, once you can lock up the front wheel more braking “power” is just a waste…

 

[cathead]

On this last photo of the cover for the left side and the parts underneath it are lots of unanswered questions. I have no idea
what it is or even what it is for. On the second photo from the top is a carb photo that has two smallish pipes that probably hook to
the unknown thing.

 

[great white]

View attachment 434051View attachment 434053View attachment 434054View attachment 434055View attachment 434056
On this last photo of the cover for the left side and the parts underneath it are lots of unanswered questions. I have no idea
what it is or even what it is for. On the second photo from the top is a carb photo that has two smallish pipes that probably hook to
the unknown thing.

Thats usually an air filter cover on vtwins, but no knowing for sure with metric cruisers.

Tubes look like emissions or similar. Don’t chuck ‘em, emissions are pretty much integrated on metric bikes and yanking them off more often than not leads to a bike thats impossible to tune and run right.

 

[pontiac428]

That's a Denso TVS. It's probably responsible for your carbs switching from choke/warm up to run, but they are also used for total BS like EGR in vehicles so equipped. I wouldn't remove anything if you don't know what it does to the system. You may not know what your spleen's job is, that doesn't mean you can live without it. Your carburetor relies on vacuum signals to manage it's many A/F circuits, and it is a highly tuned Japanese machine that ran like heck in stock form. Part of the reason why is the systems that feed the carb were intact.

 

[Deleted member 69715]

I will confess my sin...I know nothing about Viragos. I'm a Harley rider.
But, I found this. Might help.
https://www.cmsnl.com/yamaha-xv700-...slist/?filter_assembly_group=controls+&+brake

 

[cathead]

I will confess my sin...I know nothing about Viragos. I'm a Harley rider.
But, I found this. Might help.
https://www.cmsnl.com/yamaha-xv700-virago-1984-e-usa_model9058/partslist/?filter_assembly_group=controls+&+brake

Thanks a bunch! I need all the help I can get on this project. .