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From: Potage St. Germaine on 18 Mar 2007 13:55
On Mar 18, 8:28?am, tyle...(a)gmail.com wrote:

> > Did you find rubber plugs concealing the idle jets?
>
> Yes, I did.

If you go to www.partsfish.com or (www.bikebandit.com, I find
partsfish faster to use) and look at the CARBURETOR diagram, you can
see the rubber plug, item #34.

The size of the pilot jets is not given.

Item #8 is misidentified, it's actually the Main Air Jet, which is
removeable. It supplies emulsion air to the to the needle jet tube.

The pilot air jet is not shown because it's cast into the carburetor
body during manufacture.

>
> I'm pretty sure I got all the other jets clean with B12 and compressed
> air... it's just these last two "pilot air jet" holes up on top.

Just squirt B-12 through the passages and see where it comes out.

> Unfortunately there are some rubber seals on the "choke" (cold
> enrichment device) rod so I can't dump the whole thing in a bucket of
> cleaner overnight

I don't recommend actually soaking an entire carburetor in
B-12, Gum Out, STP, or whatever. I have been squirting aerosol
cleaners through the passages for 30 years now and haven't damaged any
rubber parts.

The area around the cold enrichment device really doesn't need to be
cleaned that thoroughly, the air passages are relatively huge compared
to the tiny idle mixture passages.

> Thanks a million for the info! This is all information that should
> have been in the book, if you ask me... so I'm grateful for the help.

That's what some of us are here for.

BTW, that Mikuni webpage you listed a link for is dedicated to
aftermarket racing carburetors, Harley carbs, watercraft carbs, and
carbs for old dirt bikes. It's not much use to riders who have
Japanese street bikes with CV carbs on them.


From: Potage St. Germaine on 18 Mar 2007 14:00
On Mar 18, 9:02?am, John Johnson <n...(a)invalid.com> wrote:

> http://www.factorypro.com/tech/carbtun.html
>
> How to set your carburetors, from people who know what they're doing. HTH

Bwahahahahaha! Where do you think the kids running speed shops learned
to tune carbs, if it wasn't from the original California hotrodders
who built the first superbikes and the California motojournalists who
divided their time between teaching motorcycle mechanics and writing
about speed tuning in motorcycle magazines?

From: tylernt on 20 Mar 2007 00:48
I think Google ate my first post, so, sorry if this is a dupe.

It appears that there is brass in the middle of the passage:

http://i13.tinypic.com/4bjjvc6.jpg

Sorry the pic isn't great but it's a lot more obvious in person. It
doesn't look at all like a jet with a hole in it, it looks like a
brass plug is filling the passage. And I don't see any side branch or
passage where air might flow. Any thoughts?

From: Potage St. Germaine on 20 Mar 2007 09:26
On Mar 19, 8:48?pm, tyle...(a)gmail.com wrote:

> http://i13.tinypic.com/4bjjvc6.jpg
>
> Sorry the pic isn't great but it's a lot more obvious in person. It
> doesn't look at all like a jet with a hole in it, it looks like a
> brass plug is filling the passage. And I don't see any side branch or
> passage where air might flow. Any thoughts?

Yes. That is actually a picture of the eyesocket of one of the aliens
captured after the UFO crash at Roswell. ;-)

I can imagine seeing a screwdriver slot in the brass if I study the
picture long enough. But there is no *removable* pilot air jet listed
on the CARBURETOR diagram on www.partfish.com, so the PAJ is probably
a bit of brass cast into the carburetor.

Perhaps Mikuni decided to plug a passage with brass? What would that
mean? The carburetor still needs a source of air to mix with the
gasoline coming from the idle jet.

Your mission, should you choose to accept it, is to find all the ports
and passages and jets in your idle mixture circuits and spritz them
out with carburetor cleaner.

If the hole you photographed doesn't contain the pilot air jet,
the *other* possible location of the PAJ is in the carburetor inlet
bell.

You will probably see a large brass jet with a screwdriver slot. That
should be the main air jet that mixes air with the gasoline coming
through the tube the main jet screws into.

It's on the right side of the inlet bell on my GS-1100's four Mikuni
BS34SS carburetors.

There is an oval hole at the top of the inlet for air to lift the
slide.

There should be a air hole on the left side of the inlet about 1/4
inch diameter for the cold enrichener.

There could be a small diameter hole in the inlet which is a vent for
the float bowl, if there is no vent that has a plastic tube attached
to it.

I only see three holes in the inlet mouth of my GS1100's carbs.

Somebody once did a thorough teardown and cleaning of at set of Mikuni
carbs on www.thegsresources.com. You might want to look at those
pictures.




From: tylernt on 21 Mar 2007 22:28
Made some progress tonight. I appear to be running rich if I read the
above narrative correctly. When I first start it cold, it revs to
4,000 for a brief moment then idles at the correct RPM (1,200) though
with a bit of a lumpiness. Then as the engine warms up, it idles at
4,000. Doing anything with the "choke" kills it.

The idle mixture screws were set to 5.0 and 5.5 turns. It got too dark
to continue, but tomorrow I shall try screwing them in one turn each
and see where that gets me.

> Your mission, should you choose to accept it, is to find all the ports
> and passages and jets in your idle mixture circuits

I think I found everything. The air jets are in the inlet bell of the
carb (called out in my crummy Haynes, no less), and I also saw the
oval opening for top of the slides and the opening for the "choke". I
see a hole in the float bowl on the opposite side as my mystery hole
which may be a vent, but I'm not sure where it goes. I'm left hoping
that my mystery hole is just a leftover from the manufacturing process
to create the passage for the idle mixture screw or the three little
transition ports.

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