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From: nomorespameventhoughthejapanesespamgivesmeachuckle on 6 Jul 2006 22:50

Beto(a)Mountain.net wrote:
> On 6 Jul 2006 13:55:20 -0700,
> "nomorespameventhoughthejapanesespamgivesmeachuckle" <nousenetspam(a)gmail.com>
> wrote:
>
> >
> >Mark Olson wrote:
> >> nomorespameventhoughthejapanesespamgivesmeachuckle <nousenetspam(a)gmail.com> wrote:
> >>
> >> > Fuel is leaking from the carbs because the vacuum is not operating
> >> > which means the petcock is effectively in the prime position. This
> >> > would be the same as having just an inline fuel valve with a simple
> >> > on/off switch and leaving it in the on position overnight. You too
> >> > would wake up in the morning with flooded carbs; it has nothing to do
> >> > with the floats or needle valves since the gravity is forcing the fuel
> >> > into the carbs whether they are asking for it or not.
> >>
> >> Please enlighten us- how does a carb 'ask for' fuel?
> >>
> >> If carbs are overflowing grossly, their inlet valves are not working
> >> properly, which, for the hard of thinking, is a totally independent
> >> fault from a leaky petcock, vacuum or otherwise.
> >>
> >> Yes, vacuum petcocks exist because carbs can be operating properly yet
> >> still leak *a bit* of fuel past their float valves, but carbs in good
> >> condition can and do tolerate fuel pressure (from a gravity feed system)
> >> indefinitely. My '77 KZ650B1 and '81 CM400T carbs never overflowed
> >> despite forgetting to turn the petcock off on numerous occasions.
> >>
> >> --
> >> '01 SV650S '99 EX250-F13 '98 ZG1000A-13 '81 CM400T
> >> OMF #7
> >
> >Carbs ask for fuel by the floats lowering when the fuel supply in the
> >float bowl gets low. This in turn opens the float valve letting more
> >fuel in. Since the carbs are full, the float would normally not sink,
> >and therefore the carbs wouldn't "ask" for any more fuel. Since the
> >petcock is bad, fuel is forced down into the cabs whether it wants them
> >or not.
> >
> No No No !!!!!!!!
> >
> >
> >If I put three and three together:
> >
> >Before last week my petcock didn't leak and neither did my carbs.
> >
> >Then my petcock started to slightly leak (drip drip) leak if I took the
> >tube off the tank; only my fourth carb leaked.
> >
> >Now my petcock really leaks (constant flow); now all my carbs leak.
> >
> >It sure seems to be a problem with the petcock and not the carbs.
> >
> >
> >The carbs do not leak out of the breather, but instead the leak is
> >seeping out of the drain-screw in the float bowl and is making its way
> >past the gasket between the carb body and float bowl.
> >
> >Hope this makes sense.
>
> Do you have crud in the gas tank?

There is a slight rust/gunk in the tank but nothing much. Once in a
while I see a flake against the petcock filter when I take out the
petcock. I put in an aftermarket in-line fuel filter and there is not
a bit of junk on it so I doubt anything is getting through into the
carbs. As a side note, when I take apart the petcock there is no
rust/gunk ever inside it.

From: nomorespameventhoughthejapanesespamgivesmeachuckle on 6 Jul 2006 22:55
If I don't understand how these carbs work correctly (as No No No!!!)
probably indicates, can someone enlighten me?

I looked all over the net and through Google Images and I couldn't find
a nice diagram that explains what's going on inside. The way I
understand it is the way in which I wrote about before.

From: sharkey on 7 Jul 2006 06:39
nomorespameventhoughthejapanesespamgivesmeachuckle wrote:
>
>>But more importantly, why is fuel leaking out of your carbs anyway?
>>Seems odd to have all four floats sinking/needle valves leaking?
>
> Fuel is leaking from the carbs because the vacuum is not operating
> which means the petcock is effectively in the prime position. This
> would be the same as having just an inline fuel valve with a simple
> on/off switch and leaving it in the on position overnight.

Have airhead BMW. Not vacuum taps. Rarely remember to turn off.
Doesn't leak. Try again.

-----sharks
From: Rob Kleinschmidt on 7 Jul 2006 15:15
nomorespameventhoughthejapanesespamgivesmeachuckle wrote:
> If I don't understand how these carbs work correctly (as No No No!!!)
> probably indicates, can someone enlighten me?
>
> I looked all over the net and through Google Images and I couldn't find
> a nice diagram that explains what's going on inside. The way I
> understand it is the way in which I wrote about before.

Sombody correct me if I misstate anything please.

Bikes with carbs typically do not have fuel pumps.
Without a fuel pump, bike carbs are fed by gravity.

In an older bike, the petcock is a simple on/reserve/off valve.
In a vacuum operated petcock "run" is activated by vacuum
and "start" should be gravity flow.

Fuel pressure is the weight of a column of gas about 6" - 12"
high, depnding on the bike layout and how full the tank is.

When the float bowl is full, the floats should have enough
bouyancy to press the float valves closed against the weight
(pressure) of the column of gasoline.

If the float bowl is overflowing it's because either the floats
or the float valves aren't doing their job and probably need
replacement.

Hope this helps.

From: John Johnson on 7 Jul 2006 17:20
In article <1152299700.155552.152440(a)h48g2000cwc.googlegroups.com>,
"Rob Kleinschmidt" <Rkleinsch1216128(a)aol.com> wrote:

> nomorespameventhoughthejapanesespamgivesmeachuckle wrote:
> > If I don't understand how these carbs work correctly (as No No No!!!)
> > probably indicates, can someone enlighten me?
> >
> > I looked all over the net and through Google Images and I couldn't find
> > a nice diagram that explains what's going on inside.


http://www.powroll.com/tech_specs_jetting101.htm

This site claims to be an introduction to carburetors. I only glanced
over it and it seemed ok, but I'm not sure how well it will answer your
questions. At the very least, it should allow you to ask more precise
questions here.

Also check out the wikipedia entry on "carburetor."

> > The way I
> > understand it is the way in which I wrote about before.
>
> Sombody correct me if I misstate anything please.
>
> Bikes with carbs typically do not have fuel pumps.
Well, mine's got both ('94 VFR750), but yeah. ;-)

> Without a fuel pump, bike carbs are fed by gravity.

[snip]
>
> When the float bowl is full, the floats should have enough
> bouyancy to press the float valves closed against the weight
> (pressure) of the column of gasoline.
>
What the floats do is press a tapered needle with an o-ring near its tip
into the fuel supply port, sealing it. In the diagram at the powroll.com
site, it's #34.

> If the float bowl is overflowing it's because either the floats
> or the float valves aren't doing their job and probably need
> replacement.

--
Later,
John

johajohn(a)indianahoosiers.edu

'indiana' is a 'nolnn' and 'hoosier' is a 'solkk'. Indiana doesn't solkk.
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