The illustrated carburator guide

[andyb]

This is a float needle seat.  It's not technically from an FJ, but it's from a Mikuni BS carb, so it's interchangable physically.  There are two types used on the FJ, and differ in the size of the orfice inside, one is used on gravity fed models, and one is for the fuel pump versions.  Here is a listing of stock numbers for the various years.
A - This is the o-ring that frequently leaks.  Replacement info.
B - This is the portion that was sticking out as shown as this picture shows as "C".
C - This is a plastic cap with a screen in it.  Not all bikes will have this.  The screens can plug and cause starvation issues, and are not required on bikes with fuel filters.

[andyb]

This is the diaphram cover and spring.

A - The cover.  Not much to talk about there.
B - The spring.  This is a DynoJet spring, as it's more widely spaced between the coils than OEM.  (Thanks Trav!)
C - This is a little indentation that the spring must be held within when you put the cover on, or it'll fold over sideways and do funny things to the way your slides move.

[andyb]

This is looking down on the carb.  The diaphram cover, diaphram/slide/needle assembly, and spring have been removed.  Also the main jet appears to be missing.

A - This is the emulsion tube (/needle jet) as seen from the top.  The needle fits into it.  The light visible through it is where the main jet would screw in (from the bottom).  These are directional and only fit one way into the carb body, which is shown clearly later on. 
B - The main air passageway of the carb. 
C - The surface that the slide assembly slides against.  A little light oil on reassembly here is handy, and look for wear on these surfaces.
D - This is a little ball that's swedged into the carb body.  Don't remove it.  It's put there in the manufacturing process to plug a hole where a passageway was drilled to connect two other passages (likely the choke, but doesn't matter... just leave it there!). 

Not labled but visible is a synch screw at the very bottom to the left a bit.

[FJmonkey]

WOW!!!! (feel free to delete as this does not add to content). Awesome, I like this carb course, can I get credit if I pass? I will use this when I dive into my 86' carbs for a long over due PM. Many thanks for this effort.

[rktmanfj]

Very nice work, Andy...     

Randy T
Indy

[chapindad]

Thank Andy for the work.  This has helped me more than you can know.

[Dan Filetti]

As others have said, good work Andy.

Wish I'd had this when I did my carbs a few years back.  Instead, I remember emailing Dr. Raforth idiot questions about where certain things were.  "Where is that needle seat o-ring thingy again?"  This was in spite of having his excellent instructions.  I had the things turned around you see.  These pics would have helped with reducing the apparent idiot factor immeasurably.

Thanks to you Andy for reducing the apparent idiot factor for those from here forth.

Dan

[Travis398]

Andy, You've got too much time on your hands. 

[Travis398]

B - The spring.  Is this a DJ spring, or an OEM spring?  One has much more closely spaced coils than the other, but I don't know which is which.

Stock springs are closely spaced, here is a few
 

It seems this thread would be more useful (and easier to find) if it were posted in the carb files section

[andyb]

Thanks Trav.  And yeah, either it'll get moved or a link'll get setup someplace and stuck where it's obvious.  I'm very much not done yet, but just low on gumption as of late to finish.  Couple of involved projects ("fixing" a computer that was fine in the first place, rewiring the kawi's tail and adding a mild nitrous kit to it, racing every other weekend, etc).  We'll get there.  With luck I'll try to do a cam shimming and possibly a starter rebuild also, just a question of time and gumption.

[NJona86FJ]

  legend

[andyb]

This is a slide assembly as viewed from the top. 

A - This is the diaphram.  It should be pliable and intact (no cracks nor holes); if it's not airtight the slide will not raise in response to air velocity under the slide.  Some have fixed theirs with plasti-dip or comparable products.
B - This is inside the slide.  Nothing really going on here.
C - This is a plastic ring that permanently attaches the slides to the diaphrams.
D - This is a small plate with two screw holes and two "bites" taken out of it, looks like a very fat "H" laying on it's side.  This retains the needle itself within the slide.
E - This is a stainless steel screw that replaced the bullshit soft JIS OEM screw.  There's two of these retaining the plate (D) that holds the needle in place.
F - This is a tab on the diaphram.  In the prior post, you can see where it slots neatly into the carb body to help locate and orient things.

[andyb]

This is the slide assembly as viewed from the bottom.

A - This is the slide, and it rides against aluminum in the carb body.  Look for galling or funky scuffing and such.  Polish out any gouges if you find them (unlikely but possible) to ensure smooth operation.
B - This is an air bleed.  Some carb kits (Dynojet for one) include a drill and suggest drilling these holes bigger, or adding an additional hole.  Isn't really necessary in the FJ normally.
C - This is the needle itself.  Yes, it's filthy, and I fully expect you to replace yours if they look this bad.  Definitely replace them if they're bent, also.
D - This is a little hole that part of the needle retention setup slots into.

[andyb]

This is a needle with some bits on it.

A - Yup, that's the needle. This one is a DJ needle.  OEM US models only had one slot at the far left, aftermarket and non-US models will have several slots.
B - This is a plastic retainer.  The nib on it slots into the tiny hole noted in the prior posting as D.
C - This is the clip that you adjust needle height with.  
D - This is filth and wear.  You don't want to see this.  

Not shown are adjustment washers.  Even a OEM US-market needle can be adjusted to a degree.  By placing a washer between the E clip and the plastic retainer, you will raise (richen) the needle by thickness of the washer.  If my tired memory serves, the clip positions are 2mm (0.080") apart, so a 1mm (0.040") washer can give you half-position changes.  Or you can use 0.005" shim stock and dial things in perfectly, but really by that point you should be lathing up your own needles and using an eddy-current engine dyno to check.  That's assuming you use dead consistent fuel from sealed containers and so on.  It's a descent to madness, madness I tell you...

[andyb]

This is the emulsion tube, also called a needle jet.

A - This end is threaded, the main jet and a washer secure it into the carb body.
B - This is a slot that fits into a tiny pin in the carb body, ensuring that it's oriented correctly.
C - There's four sets of these holes, spaced around the unit.  Make sure they're all clean!
D - This is why orientation matters on these.  The needle fits into this end and this is a little guide.  As a guess, I'd say that it creates a low air pressure zone behind it that helps to dispense the fuel that passes through this area and provides atomization.  So grinding this off in search of more airflow is probably unwise.

When you've got this out, hold it up to the light and look through it.  The needle is of a harder material than this (which is brass), and can wear the opening (near 'D') into an oval shape.  If that happens, you'll be untunably rich through the lower midrange/slight accelleration conditions.  If you can't decide if it's round or not, stick one of your needles into it and hold it up to light, any imperfections should be pretty readily apparent at that point.