First off, a disclaimer or two:
This is meant to be read hand-in-hand with SOG's carb cleaning guide (http://www.fjowners.com/index.php?topic=655.0).
The carbs pictured were taken off a heavily dragraced FJ that has not run in a few years. Worse, they were not drained properly. They're filthy, inside and out, but the critical passageways are absolutely clean to where you could eat off of them (if you don't mind the taste of leaded fuel).
In short, this is closer to the "before" picture than the "after" picture that you should have when working on your own FJ. So please, don't blow me a bunch of shit about how filthy things are.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_03_57_0.jpeg)
This is a rack of FJ carbs, the engine side is facing you. There's UNI pods on the backside, and you can see the throttle blades sitting closed at this angle.
A - This is the idle adjustment screw.
B - The long rod is connected to the choke actuators on each carb by a screw that fits into a divot.
C - There's three of these screws between the carbs, surrounded by linkages with springs in them. They are for adjusting the synch.
D - There are four of these caps, only one is marked. They're retained by four screws each, and cover the diaphram/slide assembly.
E - This is where the throttle cables connect to the carbs, they're adjustable for free play at this point.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_03_58_1.jpeg)
This is the carbs as seen from the back, mostly all you can see is the filters and the diaphram/slide covers. The pair of screws visible above the worm-clamps on each carb holds them together.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_03_58_2.jpeg)
The carbs as seen from below.
A - These are the drain screws. There is one on each float bowl, and they're used for emptying the carbs of fuel, which will pour out of B all over the motor, so connect a line before you loosen them. Odds are they are frozen in place though, and are easily stripped out. Easier to run the bike empty of fuel by shutting the gas off and letting it idle until it dies.
B - As stated above, this is the drain for each carb bowl.
C - The adjustment screw for changing your idle rpm.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_03_59_3.jpeg)
This is the carbs as seen from above, or what you'd see after pulling the tank. Is the OEM airbox also in the way? They connect to the intake rubbers at the bottom (as viewed in this picture).
A - This is the idle mixture adjustment screw. Each carb has one. FactoryPro (http://www.factorypro.com/tech_tuning_procedures/tuning_carbtune,CV,high_rpm_engines.html) has a good section on adjusting these.
B - This is the screw that connects the choke actuation rod to each choke plunger. If these are loose/missing, that carb won't have a working choke.
C - This is the carb balance/synch screw for adjusting #1 and #2.
D - This is the choke actuation rod, as described in B. When you pull the choke knob fully out, it should move about a half inch sideways.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_03_59_4.jpeg)
This is a float bowl, with the gasket stuck to it. Four screws held it on, through the holes in each corner.
A - This is a deep hole machined in, it fits over a protruding tube from the carb body. The choke picks fuel up from here.
B - The gasket is stuck to it.
C - If you opened the drain screw on the bottom, it would take fuel from here until it's empty.
D - This is old gas, rust, and assorted grunge. It shouldn't be here. It's also quite difficult to remove, you'll see that I've only cleaned it partially off.
E - This little hole connects with A, and if it's plugged up with D, will prevent the choke from working properly.
F - This little alcove is where the float posts fit. Once the bowl is in place, the float retention pin can't work itself out very far because it'll hit the bowl in this area. If you see a wear mark here, it means that there's been a loose float pin rattling around and hitting here.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_04_00_5.jpeg)
This is the carb as seen from the bottom, with the bowl removed. At this angle, the air filter/airbox would connect to the bottom, and the top would be stuffed into the intake rubbers.
A - This is a float. It's one big horseshoe shaped piece with plastic on the ends and aluminum in the middle. At this angle it looks roughly like a U.
B - This is the main jet. It controls fuel at high rpm/big throttle openings. It also retains a washer and the needle jet/emulsion tube.
C, leftmost - This is a bowl vent. It's usually connected to a hose that runs down past the motor and prevents gas from covering the engine if there's problems (stuck needle floats!)
C, middle - Why are there two C's? Good question. The one near the main jet is where the pilot jet lives, quite deeply in there.
D - These are air intakes for the choke circuits. They also probably have hoses connected to them.
E - It's hard to see, but that's a hollow tube that is sticking towards the camera, you're seeing it nearly end-on. That's the tube that pokes into the carb bowl and carries fuel up to the choke circuit.
F - This is the center portion of the float assembly, and you can see the little wire clip hanging over it. Bending this little tang up or down is what adjusts the fuel height/float height.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_04_00_6.jpeg)
This is the bottom of the carb with the bowl removed, as seen from a different angle. The airfilter/airbox would be connected to the side nearest the camera. All markings are as listed above.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_04_01_7.jpeg)
This is the carb with the bowl removed, as seen from the airfilter/airbox side.
A - This is the pilot air jet. Stock is a 155, and that works for most folks.
B - This is the air passageway that communicates with the diaphram area. If you put a light vacuum on this (suck on it, but clean it first, ewww) and have things assembled, the slide should move. If it doesn't, odds are you've got a torn diaphram or the slide is jammed/siezed up.
C - This is the slide. If you stick your finger under it and shove it up (down and to the right in this picture), it'll move and then return when you take your finger out.
D - This is the needle. It's adjustable, but you can't see that from here.
E - This is the top portion of the needle jet/emulsion tube. See how the needle goes into it, the needle is tapered, and as the slide moves up, there is more area for fuel to come up and go into the engine.
F - This is the float needle's seat, as seen from the side, under the middle part of the float.
G - Another view of the main jet.
H - Another view of the float.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_04_01_8.jpeg)
This is a pilot jet.
A - This is the orfice that meters fuel. It's tiny, really, really tiny.
B - This is the jet. Usually these are 37.5, 40, or 42.5.
C - This is a typical Bic lighter, for size comparison.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_04_01_9.jpeg)
This is a pair of pilot jets in my hand. Notice the lack of hair on the palm. There's two types of jets.
A - This type has holes on the sides. These don't have any bearing on the fueling, as they're not the metering orfice, they're huge by comparison. Grunge can form in these holes, break loose, and ruin your day, so it's something to have clean before you put them in.
B - This type lacks holes on the sides. This is what was OEM.
I believe the OEM lacks the holes; the holes were in theory to make it less likely to plug and easier to clean. Seems strange, but they have no bearing to fuel flow. They can however collect junk that breaks off and plugs the metering orfice, so clean them up good anyhow.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_13_0.jpeg)
This is the idle mixture screw assembly, removed. In a stock US carb, this is covered by a pressed in plug.
A - This is the screw itself.
B - This is the spring that puts tension on it.
C - This is where it goes into the carb.
D - This is the choke rod. Not a bad idea to lubricate it where it goes through the carb bodies.
E - This is the screw and paul that hold the choke rod to the choke plunger. The screw sits in a divot.
Not shown is the washer and tiny o-ring. The o-ring provides a seal that prevents fuel from coming up and out past this screw, and the washer prevents the spring from chewing the o-ring apart. Then the spring sits on the washer, and the screw goes in last (though it's easiest to put it all in at once, it's nearly impossible to take it all out at once).
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_13_1.jpeg)
This is a view looking into the carb from the motor side.
A - This is where the mixture screw feeds into the airstream going into the engine. It's not really very visible (I really did try, but a photog I'm not!), but I've screwed the mix screw all the way in, and it's sticking out a bit.
B - Yup, that's the throttle blade, or butterfly valve. Twist the throttle, and that's what you're moving.
C - There's 3 (right?) tiny holes here, right about where the throttle blade nearly touches. That's where the pilot jet feeds fuel to.
When you're cleaning a carb, one of the critical areas to get clean is to use forced carb cleaner and/or compressed air into where the pilot jet screws in (see a few pictures higher in this thread). It should come out the holes shown in C in a good strong stream from each. If you remove the idle mixture screw and blast down it, it'll mostly come out of hole A. Covering that hole with your finger and spraying carb cleaner into where the idle mix screw was will clean the passageway that feeds it (otherwise your idle mix screws will have little to no effect as they're not being fed anything to distribute).
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_13_2.jpeg)
This is the bottom of the carb (it's upside down on the bench, and the camera is pointed down), with the bowl removed, the main jet removed, and the washer under the main jet removed.
A - This is the float assembly.
B - This is the emulsion tube/needle jet. Notice the slot cut into it on the bottom left side. That is fitting over a pressed-in pin to properly orient the emulsion tube.
C - Another view of the tang on the float assembly. The wire clip over it is connected underneath to the float needle.
Not labled but visible on the right is the fact that the float pin has been pushed out a bit, perhaps 1/8", towards the top right of this picture (directly to the right of the "c" in the picture). A quick tip for making that easier? If you get too rough, those float posts will break off entirely too easily. Make a little spacer block to sit between them and distribute the shock of tapping the pin in or out against both posts.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_14_3.jpeg)
This is the float assembly, with the float needle stuck to it.
A - This is the float needle's rubber tip. This is the little bastard that's usually responsible when you find a puddle of gas under your FJ, assuming the float needle seat orings are intact.
B - This is the tang for adjusting fuel level/float height, as seen from the bottom. The float needle's little wire clip is keeping the needle connected, but if I sneezed while taking this picture, I'd probably still be looking for the needle.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_14_4.jpeg)
This is the carb body, as seen from below. The bowl, main jet + washer, float assembly, and float needle have all been removed. Air filters/airbox would be connected to the bottom part of the carb in this view.
A - This is the emulsion tube/needle jet. You can barely see that it's threaded, that's where the main jet goes (with a washer between the two).
B - This is the float retaining pin (over to the right, the B is hard to see).
C - This is the needle seat.
D - This is the screw and little clip that retain the needle seat.
E - Overflow tube.
F - Choke air intake tube.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_15_5.jpeg)
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 (http://www.fjowners.com/index.php?topic=47.0) is a listing of stock numbers for the various years.
A - This is the o-ring that frequently leaks. Replacement info (http://www.fjowners.com/index.php?topic=1391.0).
B - This is the portion that was sticking out as shown as this (http://www.fjowners.com/index.php?topic=4281.msg37759#msg37759) 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.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_15_6.jpeg)
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.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_16_7.jpeg)
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.
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.
Very nice work, Andy... :good:
Randy T
Indy
Thank Andy for the work. This has helped me more than you can know.
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
Andy, You've got too much time on your hands. :good2:
Quote from: andyb on June 21, 2011, 11:12:35 AM
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
(http://fjowners.com/gallery/2/486_08_07_11_8_32_54.jpeg)
It seems this thread would be more useful (and easier to find) if it were posted in the carb files section
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.
:good2: legend
(http://fjowners.com/gallery/2/10_18_05_11_2_06_16_8.jpeg)
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.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_06_17_9.jpeg)
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.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_08_03_0.jpeg)
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...
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_08_05_1.jpeg)
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.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_08_08_2.jpeg)
This is a blurry picture. Sorry about that. It's also of the needle and associated parts again.
A - Needle.
B - Plastic retaining thing.
C - Clip.
D - Washer. Sits atop the clip (to the bottom right as viewed here) and prevents the spring from getting into the clip, breaking, and going through the motor.
E - The spring. This allows the needle to move around a bit rather than being absolutely rigidly mounted.
F - This is the plate that retains the needle, sundry washers/clips/crap and spring in the slide.
G - A lovely socketheaded stainless screw with locknut that holds 'F' to the slide assembly. There are two, you can see the other sticking through the retaining plate.
(http://fjowners.com/gallery/2/medium_10_18_05_11_2_08_10_3.jpeg)
This is the carb body as seen from below (bowl side). The main jet, washer, emulsion tube, slide assembly, slide spring, and diaphram cover have all been removed.
A - This is the little nub that dictates what direction the emulsion tube faces. If you're assembling things and it doesn't want to go, don't force it. This is likely why it's not going in properly. Line things up, maybe some lube, and try again.
B - That's a deep, dark hole. It's also the location of the pilot jet.
C - This is the tang used to set fuel height/float level. Remember?
D - This is the middle-ish part of the float.
Now for the post that I didn't want to make.
Even though it doesn't always feel like it, gasoline is flammable. Smoking is frowned on when working with carbs that are full of fuel or even still smell like it. Don't clean carbs around a campfire, got it? Also, when you're using carb cleaner, for pete's sake wear safety glasses. Yes, you look dorky. You look really stupid when you're rolling around the driveway howling in pain, clutching your head. Ask me how I know this.... When you're using carb cleaner and spraying it into a plugged passageway, it's like turning your kitchen faucet on full blast into a thimble (don't try that if the wife is home, incidentally, and have towels handy)... it WILL spray directly back at you and hit you in the face. It burns like f'king fire if it hits you in the eyes. I also wholeheartedly suggest that you have a fire extinguisher in your garage/work area (as well as a couple in the house, with smoke detectors, look both ways before crossing the street, etc). However something that you may not have is a portable eyewash. Get one, and store it next to the fire extinguisher or in the top of your toolbox, someplace very accessable. They're inexpensive, and you don't want to have to run through the house to the medicine cabinet to get your eye washed out; again, I speak from experience. If you do get carb juice or gas in your eye, wash it out immediately. Go to a sink or use the eyewash bottle, and tilt your head in such a way that the bad eye is down (so you don't flush the crap into the other one). Hold your eye open, and flush under running cool water for a solid fifteen minutes. It will feel ridiculous after the first three minutes. Do it anyway. Carb cleaner will cause your eye to swell in a very nasty way and hurt like a bitch in the process.
Carb cleaner is capable of destroying a variety of things, including the surface of some tables. Don't clean carbs on the kitchen table, your grandfather's priceless antique desk, etc.
Use your head and you'll get to keep it.
I was going to go through and add part numbers, but not everything interchanges between the years. Instead, I'm going to point you to this post (http://www.fjowners.com/index.php?topic=1832.msg14500#msg14500). Between the parts diagrams and these photos, you should be able to figure out what you need. My personal advise is to go to RPM (http://www.rpmracingca.com/products.asp?cat=24) for your parts, though depending on where you're located you may have to look for alternate sources. This (http://www.rpmracingca.com/proddetail.asp?prod=carbkit&cat=24) kit is the current source for all of the kickass stainless hardware that my carbs are wearing, and it's unquestionably some of the best money you can spend on your bike, making working on the carbs a zillionty times easier.
I'm also going to point you to this post (http://www.fjowners.com/index.php?topic=1832.msg14515#msg14515) which describes the original equipment jetting as from the factory. Then I'll point you to places like the carb section (http://www.fjowners.com/index.php?board=21.0) for more information on troubleshooting and modified jetting for various combinations.
Past that, you can always post questions in a new thread someplace, or use the lovely search (http://www.fjowners.com/index.php?action=search) feature. Remember that when you have a modified bike and are looking to make changes, you need to take into account air density/elevation, and that different people have a different idea on what "running well" means! The other thing I'm going to say is that if you think you're decidedly lean on any portion of the fueling, ensure that the carbs are CLEAN prior to changing jets. A partially plugged jet is going to act like it's several sizes smaller than it really is, so you may end up cleaning and rejetting and becoming vastly rich--but it'll be better than it was and you'll not keep tuning because of your minor improvement with still so-so results.
Thanks Andy. I'm thinking I might need to bite the bullet and pull and clean mine and not be so lazy. I however couldn't help but laugh at the carb cleaner eye protection lesson. It reminds me of a very embarassing lesson learned with a combo of weed, tabasco sauce, and scrambled eggs, one morning with my golf buddies prior to a tournement. FYI, DON'T look INTO said bottle while rapping it on the table (note weed/stoner referance). Man, I played some shitty golf that day. :wacko1:
thank you
regards
Cash
Andy,
Although I've done many hundreds of Mikuni carbs from single to multiple setups, it's always good to see what you are up against and what they look like before and as you go through them.
I can say from experience this is some great information. Very nicely done sir.