carb bench test?

if a person was to seal the inlet and outlet of a carb then pull a operating range vacuum on it would this prove the butterfly shaft seals ?
or is there a vent somewhere ? on the bench would be the place to do this sort of thing, i think
the rack would have to be broken down, to test individual carbs, or the whole rack sealed and that might be tricky
this might be a pain to do but you would be confident the carbs were in good shape
could the threads on the idle mixture screws be a vacuum leak,and what would be a max vacuum number
i need to go for a ride before i break somthing

 

Sounds feasable, provided the seal of the inlet and outlet includes all of the orifaces of the inlet (air jets, etc).

Correction: You would have a dickins of a time sealing up the fuel system unless you seal all four carbs simultainiously (quite a challenge, but doable).

 

first results show what i would call bad leaks at 2 and 3 low speed mixture screws, past the threads, 1 and 4 tiny leaks
that took about a minute to find
can't do any more till my extra set of hands comes home

 

Interesting idea Polock.

I can't tell from your pictures, but I would use some kind of rubber gasket material to help seal the carbs to your 1 x 4's.

In the set up you show, where are you pulling the vacuum? How are you checking if the seals are leaking?

Just a thought, if you use a small amount of pressure and brush on some soapy water to each shaft seal you could see bubbles forming on the ones that leak!

 

kind of hard to see, but there is a piece 1/4" cork gasket material on each end, it's the same color as the wood
so far just some mouth PRESSURE on the fuel line, there's still some gas in the bowls, yuck
i could hear it then isolated it with new fuel line in the ear
soapy water is a good idea, you been talking to Ramon ?
maybe some teflon tape on the threads of the mixture screws?

 

I like Nick's variation.

Slight pressure - Maybe output from shop vac or the compressor set at a very low pressure (maybe 5 psi.)

Don't worry about the pilot screws. Just look for bubbles elsewhere.

 

All you have to do to seal the Mixture Screws is what ought to be done the moment the Bikes Dialed-in.

Add a small Dab of Bathtub Sealing Calk to the top of the orifice. The Caulk will cure and make an air and moisture tight seal.

The "Plug" it makes will pull-out of there with a minimum of fight. Usually in one whole piece.

I like the idea of a testing Jig.
I wonder if a High-powered Shop Vac could but enough vacuum to a Plenum to actually synchronize a rack before sending them back to a Mail Order Cleaning client???

 

Very interesting idea. You should be able to find where the vacuum leaks are. You should see that the float gaskets, and the slide diaphragm are leaking too. where do you come up with this sh!t??

 

The Academy of Brilliance in Motorcycle Tuning

 

the problem i see with sealing the hole after the carbs are dialed in is they won't be dialed in anymore since the screw was set with a leak then the leak was taken away
i think the pressure test is good for a "quick and dirty" but some seals are made to work one way or the other pressure or vacuum
since i have no idea where to start, going to go with 5 psi and 15 in/hg
while they still have gas in the bowls i could test pressure with a match

 

10 inches of mercury ought to do just fine Rick! I'm pretty sure your Vac can handle it.
Polock, you are a true thinker! I love the rig! I'd only offer that a sheet of rubber would give a much better seal (old truck inner tube) than cork, but, since it works, who is to argue? You get the gold star award for the week!
Rick's RTV plug idea is just the ticket for those mixture screw leaks although it does bring up the question as to why they aren't sealing with the o-rings in place???

 

I can't imagine enough air getting around the Mixture Screw having any measurable effect on an Air~Fuel Ratio.

If the thing was that loose ... It would be falling-out of the Carb ... right?

This seems pretty close to Barking at the Moon.
But, I'm waiting for the Official Results.
I'm keeping my mind open.

While were still young.
Do you guys think I could buy a YZF-R1 and set about transferring the Fuel Injection over to the XJ-Bike?

Is this within the realm of possibility?

 

Why not? You got enough money and time anything is possible.

 

If you have a complete donor bike with a good computer, it would just take time to wire it together, plumb in any sensors, and test and tune. Not sure how the R1 fuel delivery system is set up, but with a little creativity could definitely be a fun winter project.

 

You know, I don't think you need to worry about mixture screws leaking. I believe that is what the rubber donut below the washer and spring is for. All the fuel/air is below that down on the narrower part of the needle I believe.

In fact, leaks at the mixture screws would indicate a problem with the donuts.

 

round two
vacuum tank and pump setup, 15 in/hg ,floats removed hit the valve and the pilot screws don't leak anymore, all i can figure is the pilot screw spring washer oring is kind of like a check valve, one way only
but the gauge still falls to fast, take out the choke rod and rubber caps and now it's easy to tell they all leak a little, adds up to a lot
15in/gh to 0 in six alligators then i sealed them with some putty and got to
30 alligators and quit counting with 5in/hg left
tomorrow going to shine the plunger and seat, maybe try to fit a oring on the shaft between the spring and cap

 

leaks at the mixture screws would be so minimal.
In fact the leakage through the threads on the screws wouldnt be enough to really make a noticeable difference..... unless the threads were so shot that they were totaly sloppy....then you would just about be able to pull them straight out.


I'd just seal them if desired and forget them till next time

 

You'll have some precision machining to do to add an O-ring to the Enrichment Plunger.

You don't suppose the Engineer's made it that way for a reason ... huh?

The O-ring will need a Placement groove or it will ride up and down on the shaft until I quit laughing about what a sick joke I might have had going here if I had my MoJo Working.

But you get the idea.

Knock; knock.
Who's there.
Orange.
Orange who?
Orange you glad I didn't take that joke possibility and run with it!

 

how can i micro-tune, one degree at a time to within a gnat's whisker of perfection if if there's a leak anywhere
one wrap of teflon tape and it's a non-issue, two wraps and one might be able to throw that o-ring away, here we go again
more on that later
after a closer look, the "choke" plungers were made to leak, there is a direct path in the enrichment circuit
plunger up or down, the only thing in the way is the rubber cap on the plunger stem, this must be the vent for expansion in the bowls
anyway the problem was found, the two nuts on the butterfly shafts were a little too tight, not letting them close the last bit smoothly
acts just like a vacuum leak
now i've got to take off a perfectly good tuned rack and start all over
how do i get myself into this stuff