Discussion:
mikumi carbs
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spud
2005-09-29 19:11:25 UTC
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I have a GS750 1977, the engine is from a 1978 bike and the carbs are o
my original engine, where can I find out the carb settings for them, a
I have inadvertantly adjusted the screws on the bottom of the carbs an
Iv'e been told that one of these is the fuel metering screw....
Can anyone help
I found this forum by looking for mikumi carbs,
Hello to all......

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spud
"jamison" <@ .com>
2005-09-29 23:12:45 UTC
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I would check out the forum at www.thegsresources.com . There are some guys
on there (Keith Krause, Earlfor, just to name a few) that know the Mikuni
VM-series carbs that you have like the backs of their hands.

I have the same model/year bike as you. I can tell you that generally, the
fuel mixture screw on the bottom front of each carb should be roughly 1-1.5
turns out if the bike is stock. You want to make sure that when you are
tightening these screws to seat them LIGHTLY. Ever so lightly. Reason being,
this screw comes to a very sharp tip up inside the carb body and if you
tighten it in, the tip can break off and cause NIGHTMARES. Just believe me
when I say I have been there ;-).

The GS Resources is a wealth of info for these bikes. I would definately
recommend checking out the forums.
I have a GS750 1977, the engine is from a 1978 bike and the carbs are of
my original engine, where can I find out the carb settings for them, as
I have inadvertantly adjusted the screws on the bottom of the carbs and
Iv'e been told that one of these is the fuel metering screw....
Can anyone help
I found this forum by looking for mikumi carbs,
Hello to all.......
--
spud
r***@gmail.com
2005-10-11 20:02:23 UTC
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Not sure what the problem is, but GS Resources seems to be down. Not
sure if they missed a payment for their hosting or what. Hopefully
they'll be back in business soon, as I just bought a 1980 GS850GL over
the weekend.

Randy...
krusty kritter
2005-10-11 21:21:09 UTC
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Post by r***@gmail.com
Not sure what the problem is, but GS Resources seems to be down. Not
sure if they missed a payment for their hosting or what. Hopefully
they'll be back in business soon, as I just bought a 1980 GS850GL over
the weekend.
The URL is something like "thegsresources.com" not just
"gsresources.com". I can see where people think they are getting into a
motorcycle site and search it for Suzuki information.
m***@gmail.com
2015-07-14 23:50:40 UTC
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Guys yes indeed their is bottom mounted carb mixture screws on my original 1977 gs750 B model and I also need to know where to set them.

Thanks for the help if anyone knows.
DT

krusty kritter
2005-09-29 23:41:19 UTC
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I have a GS750 1977, the engine is from a 1978 bike and the carbs are of
my original engine, where can I find out the carb settings for them, as
I have inadvertantly adjusted the screws on the bottom of the carbs and
Iv'e been told that one of these is the fuel metering screw....
The original equipment carburetors on the GS750 were slide valve
carburetors. If you go to www.partsfish.com and register, you can look
at the carburetor fiches and see what I mean.

The idle mixture screws are called "pilot air screws". They are NOT on
the bottom of the carburetors. They are on the sides of the
carburetors, pointing down at a 45 degree angle. (1)

This makes it really easy to squirt aerosol carburetor cleaner through
them if the idle mixture ports get plugged up.

Since they are AIR screws, turning them clockwise makes the mixture
richer, turning them counterclockwise makes the mixture leaner. About
1-1/2
turns from fully closed should do the trick.

(1) That business about you adjusting the screws on the BOTTOM of the
carbs makes me wonder just what the heck you were turning. The drain
plugs
in the bottom of the float bowls?
VM
2005-09-30 19:34:13 UTC
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For someone who comes across like a complete asshole who thinks he knows
everything about motorcycles, you have proven that you are exactly that.

The screw he is talking about is the Pilot Fuel Screw. It, along with the
AIR SCREW you were talking about, determine how much air and gas are used in
the pilot circuit. Here's a picture of what it looks like:

Loading Image...

and here is where it goes on the carb:

Loading Image...


Krusty, feel free to not give us one of your 500 word minimum posts when you
have no clue WTF you are talking about.
Post by krusty kritter
I have a GS750 1977, the engine is from a 1978 bike and the carbs are of
my original engine, where can I find out the carb settings for them, as
I have inadvertantly adjusted the screws on the bottom of the carbs and
Iv'e been told that one of these is the fuel metering screw....
The original equipment carburetors on the GS750 were slide valve
carburetors. If you go to www.partsfish.com and register, you can look
at the carburetor fiches and see what I mean.
The idle mixture screws are called "pilot air screws". They are NOT on
the bottom of the carburetors. They are on the sides of the
carburetors, pointing down at a 45 degree angle. (1)
This makes it really easy to squirt aerosol carburetor cleaner through
them if the idle mixture ports get plugged up.
Since they are AIR screws, turning them clockwise makes the mixture
richer, turning them counterclockwise makes the mixture leaner. About
1-1/2
turns from fully closed should do the trick.
(1) That business about you adjusting the screws on the BOTTOM of the
carbs makes me wonder just what the heck you were turning. The drain
plugs
in the bottom of the float bowls?
krusty kritter
2005-09-30 22:03:07 UTC
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Post by VM
For someone who comes across like a complete asshole who thinks he knows
everything about motorcycles, you have proven that you are exactly that.
Find a message where I said that I know "everything about motorcycles"
and provide a link to that message.

Why are your panties all in a knot over my reply to the OP and my
asking about what screw he was turning? That screw certainly does NOT
appear on the parts fiche for a slide valve carb from a 1977 GS750.
Post by VM
The screw he is talking about is the Pilot Fuel Screw. It, along with the
AIR SCREW you were talking about, determine how much air and gas are used in
http://show.imagehosting.us/show/742123/0/nouser_742/T0_-1_742123.jpg
That part could be from an aftermarket rebuild kit. Provide a link to
the vendor original photograph.
Post by VM
http://show.imagehosting.us/show/742126/0/nouser_742/T0_-1_742126.jpg
Post a photograph of the carburetor in side view so we can all see if
the nasty dirty carb you took a picture of is the slide valve carb from
a 1977 GS750 or or it's actually a CV carb from a 1980-ish GS750.

Come on, now. Enquiring minds want to know what's going on here.
.
2005-10-01 02:02:23 UTC
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Here you go, from when I got the carbs from a bike that had sat outside for
a few years without being touched, to a complete clean/rebuild:

Loading Image...
Loading Image...
Loading Image...
Loading Image...
Loading Image...
Loading Image...

I realize that they do not show this screw on any parts fische because I
have had to replace one and only certain rebuild kits contain this screw. My
point is that next time, instead of just simply stating that the screw
doesn't exist because you can't find it on a fische, realize that maybe it
is something that you don't know about and shouldn't be giving someone false
information. Maybe it's possible that since the screw was supposed to be
capped from the factory due to emissions requirements, Suzuki chose to not
show them on any parts fisches/lists. Who knows. But it sure exists and your
post would have just further baffled the original poster if there wasn't any
clarification.
Post by krusty kritter
Post by VM
For someone who comes across like a complete asshole who thinks he knows
everything about motorcycles, you have proven that you are exactly that.
Find a message where I said that I know "everything about motorcycles"
and provide a link to that message.
Why are your panties all in a knot over my reply to the OP and my
asking about what screw he was turning? That screw certainly does NOT
appear on the parts fiche for a slide valve carb from a 1977 GS750.
Post by VM
The screw he is talking about is the Pilot Fuel Screw. It, along with the
AIR SCREW you were talking about, determine how much air and gas are used in
http://show.imagehosting.us/show/742123/0/nouser_742/T0_-1_742123.jpg
That part could be from an aftermarket rebuild kit. Provide a link to
the vendor original photograph.
Post by VM
http://show.imagehosting.us/show/742126/0/nouser_742/T0_-1_742126.jpg
Post a photograph of the carburetor in side view so we can all see if
the nasty dirty carb you took a picture of is the slide valve carb from
a 1977 GS750 or or it's actually a CV carb from a 1980-ish GS750.
Come on, now. Enquiring minds want to know what's going on here.
The Older Gentleman
2005-10-01 08:33:51 UTC
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Post by .
Here you go, from when I got the carbs from a bike that had sat outside for
http://show.imagehosting.us/show/742903/0/nouser_742/T0_-1_742903.JPG
http://show.imagehosting.us/show/742912/0/nouser_742/T0_-1_742912.JPG
http://show.imagehosting.us/show/742917/0/nouser_742/T0_-1_742917.JPG
http://show.imagehosting.us/show/742924/0/nouser_742/T0_-1_742924.JPG
http://show.imagehosting.us/show/742936/0/nouser_742/T0_-1_742936.JPG
http://show.imagehosting.us/show/742940/0/nouser_742/T0_-1_742940.JPG
Sure look like slide carbs to me....
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BOF#30 WUSS#5 The bells, the bells.....
krusty kritter
2005-10-01 13:26:09 UTC
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Post by .
Here you go, from when I got the carbs from a bike that had sat outside for
http://show.imagehosting.us/show/742903/0/nouser_742/T0_-1_742903.JPG
http://show.imagehosting.us/show/742912/0/nouser_742/T0_-1_742912.JPG
http://show.imagehosting.us/show/742917/0/nouser_742/T0_-1_742917.JPG
http://show.imagehosting.us/show/742924/0/nouser_742/T0_-1_742924.JPG
http://show.imagehosting.us/show/742936/0/nouser_742/T0_-1_742936.JPG
http://show.imagehosting.us/show/742940/0/nouser_742/T0_-1_742940.JPG
I realize that they do not show this screw on any parts fische because I
have had to replace one and only certain rebuild kits contain this screw.
Your pictures don't actually *show* the screw installed, and whether
it's externally accessible with the float bowl still installed. I found
*one* message on Usenet where an owner asked about a mixture screw that
was *inside* the float bowl. Nobody answered that message, either
nobody knew the answer, or nobody was interested enough to reply.
Post by .
My point is that next time, instead of just simply stating that the screw
doesn't exist because you can't find it on a fische, realize that maybe it
is something that you don't know about and shouldn't be giving someone false
information. Maybe it's possible that since the screw was supposed to be
capped from the factory due to emissions requirements, Suzuki chose to not
show them on any parts fisches/lists. Who knows. But it sure exists and your
post would have just further baffled the original poster if there wasn't any
clarification.
False information? Why would I intentionally give somebody false
information?
Why do you even accuse me of giving false information after I went out
of my way
to help somebody who asked for information? I asked the OP for more
information
about what screws he was turning, and I got a rude response from *you*
instead.

All information is "good" information, but sometimes it's not the
information the questioner is looking for. Maybe learning that there
was an oddball slidevalve carburetor with fuel mixture screws in the
float bowls will help somebody else what owns a 28 year old motorbike.

Now I've seen *two* kinds of slide valve carbs with mixture screws that
might be called "gas screws". Mikuni radial flatslide carbs also use
"fuel air screws" instead of "pilot air screws".

But there's no need to be so nasty about it. You actually went through
all that trouble just to prove that krusty kritter was wrong about
something. You had to
digitally alter an image just to prove it. What was *so* important that
you had to do *that*?

Why couldn't you just say, "No, there was *one* year of GS750's that
had a pilot gas screw, here is a picture."?

The parts fiches on www.partfish.com and www.bikebandit.com do not
include the 1977 GS750B carburetor, they show the 1978 GS750C carb and
go from there.
c***@btinternet.com
2005-09-30 13:29:15 UTC
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Post by spud
I found this forum by looking for mikumi carbs,
Google must be even better than I thought, then.... ;-)
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