Author Topic: Carburetors and their various parts,internal and external with pics.STICKY PLZ  (Read 57675 times)

Offline ben2go

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This write up pertains to the 1989-2000 GS500 Mikuni BST33SS carbs.These carbs are on various motorcycle makes and models.I am going to point out the various parts that we need to know.

Here are two good links to help understand our carbs better.

This link is really good at explaining things.Same carbs as ours just in a rack of four instead of two.Ours would be like the two center carbs.
http://www.gixxer.com/forums/showthread.php?t=159718

This link explains what each circuit of the carb does and how to tune them.There is some false stuff on our forum and this should clear some of it up.
http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html


Here is the air filter side of the carbs.


Here is the top side.


Here is the engine side of the carbs.


Here is the bottom side.


Here is the right side.


Here is the left side.




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Offline ben2go

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Now for what's on the inside.Starting at the top.

When the top of the carbs are opened up,be sure not to loose the vacuum port O ring.These things cause all kind of running issues.


The top.


The top removed.Be very careful not to loose any of the parts


Here is the slide needle laid out.


The slide has been removed.You can see the slide guide and emulsion tube.


The slide guide removed as an assembly.


The emulsion tube seperated from the slide guide.


Please be aware of the seal.I can not find these any where and I have a set of carbs with bad seals.

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Offline ben2go

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Now for the bottom side.This is the area that gives the most grief,especially to new people working on the GS500.

Here it is with the float bowl removed.Note that the jets are missing from this set.


Here is the float bowl.You can see the drain and drain screw better in this pic.


Here is the inside and this is where dirt and gunk settles.It's also where it gets sucked into the carbs,clogging them.


Float assembly has been removed.If the needle's seat O ring doesn't seal tight,it will flood the crank case with gas.


Float assembly.If that O ring or needle doesn't seal tight,it will cause running issues and flooding.



All those little passages need to be cleaned and blown out with compressed air.I used gunk brand brake cleaner on my carbs.
To use it,ever rubber part has to be removed from the carb.I didn't show the chokes being removed.They are rarely an issue and
usually a couple sprays with WD-40 will free them up.

Here is a link to the album with more pics of the carbs.This is my parts set.
http://s205.photobucket.com/albums/bb17/ben_2_go/Motorcycle%20Stuff/Mikuni%20BST33SS%20Carbs/
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Offline Twisted

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Can you post this on the GS wiki page?  :dunno_black:

Would be great to have it there permanently. Good job by the way  :thumb:

Offline ben2go

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Can you post this on the GS wiki page?  :dunno_black:

Would be great to have it there permanently. Good job by the way  :thumb:

Thanks and I am unsure about how I would do that.
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Offline Twisted

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Try this sticky - http://gstwins.com/gsboard/index.php?topic=46173.0  :thumb:

Don't know what section you would put it under though.
« Last Edit: June 08, 2011, 11:01:36 PM by Twisted »

Offline ben2go

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Try this sticky - http://gstwins.com/gsboard/index.php?topic=46173.0  :thumb:

Don't know what section you would put it under though.

Thanks.I may give it a try later.I will be busy for a while and it takes a while to move things over.
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Offline ben2go

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I need to add that the "Phillips" head screws are not "Phillips" head,they are "JIS" style screws and using a "Phillips" screw driver will result in the screws heads stripping.JIS screw drivers are available online and usually priced about the same as a quality screw driver.I use a hack saw and cut a slot in the screw heads and use a large flat end screw driver to remove them.Then I replace the screws with allen cap bolts.They are way easier to remove the next time the carbs need work.
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Offline Tombstones81

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crap good reminder about this thread, forgot to bookmark it when I first saw it.  :thumb:
94 GS500
01 Engine
Personally repainted!  (Traded)

87 Honda VF700C Magna
(Super Magna)

Offline xunedeinx

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Good reminder...

Got one for the newer carbs?  :D

Offline The Buddha

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Stuck. (past tense of stickied  O0 ).
Cool.
Buddha.
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I run a business based on other people's junk.
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Offline ben2go

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Stuck. (past tense of stickied  O0 ).
Cool.
Buddha.

Thanks.
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Offline ben2go

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Good reminder...

Got one for the newer carbs?  :D

Not yet.If I find a set or buy a bike with the newer carbs,I will def do a write up like this one.
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Offline motoDMD

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this is the single greatest sticky ever known to man.  thanks a bunch.   :bowdown:


but where were you 3 months ago tho when the hayne's manual laughed at me with it's microscopic black and white thumbnails....

 :dunno_white:

Offline ben2go

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this is the single greatest sticky ever known to man.  thanks a bunch.   :bowdown:


but where were you 3 months ago tho when the hayne's manual laughed at me with it's microscopic black and white thumbnails....

 :dunno_white:

Thanks.I was getting my bike out and doing all my spring cleaning and tune up on it.I own and use the Clymer manual and it seems to be a little better IMO.I have used both.
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Offline xunedeinx

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Good reminder...

Got one for the newer carbs?  :D

Not yet.If I find a set or buy a bike with the newer carbs,I will def do a write up like this one.

If you live near here, ill let you experiment on my bike for the benefit of gstwin!!!

Oh, and so I can learn firsthand..

Offline ben2go

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Good reminder...

Got one for the newer carbs?  :D

Not yet.If I find a set or buy a bike with the newer carbs,I will def do a write up like this one.

If you live near here, ill let you experiment on my bike for the benefit of gstwin!!!

Oh, and so I can learn firsthand..

We are a bit far apart.I'm in upstate SC.
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Offline sledge

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There is some false stuff on our forum

You can say that again  :thumb:

Offline GSnoober

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The son of a friend (about 20 years old) recently asked me to teach him some fundamental steps about how to clean / rejet motorcycle carburetors. He's studying auto repair at a local community college, and they don't cover anything about carburetion; if it isn't in the textbook, the students learn nothing about carbs at all.  I told him to read through this thread a few times so he would become familiar with the basic components of our stone-axe simple GS500 carbs, and once he could answer my questions about carburetors without screwing up, we'd advance to Phase II of his training...

Now that he has a better understanding of what he'll be working on, I'm going to pull my GS carbs off next week to clean and rebuild them with him. OK, so they don't really need any service, but we'll do it a few times anyway... I'll let him knock himself out swapping jets and washers until he can do it blindfolded. I don't think he'll ever want to become a carb guru, but I think he'll be less likely to be afraid of working on them on in the future.

Thanks for this thread, ben2go; good photos and write-up... I've been working with motorcycle carbs for so many years that I've forgotten how confusing they can be to people just beginning to learn how to turn wrenches without stripping threads, overtorquing bolts, and ruining various components. Having good photos and descriptions make a tremendous difference in the learning process; let's hope he doesn't destroy my carbs before his training is complete...

Offline ben2go

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You're welcome and happy it's helping.Good luck to you both.After a few times tearing apart carbs,it really wasn't a big deal to me.Maybe he will catch on quick and it won't be a big deal to him either.

Also give this to him to read.It will help. http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html
« Last Edit: August 07, 2011, 06:19:49 PM by ben2go »
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