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Basic Carb Tutorial


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#1
CRXfanatic

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I believe this was from Greg Gauper years ago from some IT.com discussion... I found it in my files and thought I'd share...

THE STOCK CARB WORKS FINE!

The Weber will have the same problem with emissions as the modified stock carb.
I have heard of instances in which people bolt on the Weber to their car with
the cat still installed, and had the cat get super hot!

You either need to be born with olive oil in your blood or pay somebody who does
in order to get the Weber working properly.

You will probably get 50/50 split on this site from people who say stay with the
stock vs go with the Weber. Among the people who run the Webers, you will get a
50/50 split as to which Weber to run.

In my opinion, for someone running solo or just starting out, stay with the
stock unit.

If you don't have the Weber set up properly, it will give you fits. Especially
for the stop and go action of solo. You want good throttle response with the
car turning left and right.

If you want to experiment (and save some money) use your spare carb as a guinea
pig.

Have the carb cleaned, install new gaskets, put in a new power valve and floats,
perform the legal mod's yourself. If you want advice on what to do, post
another thread. Shouldn't cost you more than $100 for the parts.

Some people DO know how to make the Weber work. A properly set up Weber WILL
make more peak power. I still have my Weber that I got from King. I struggled with it for over two years before I gave up and
went back to stock. Didn't like the drivability. Unless you are a front
running ARRC car, it's not worth it IMO.

The only problem you can run into with a stock unit is age. I did have a
boneyard carb that had a weird problem that acted like a float problem, but I
finally proved it wasn't the float by taking the top section w/float and bolting
it onto a different bottom section and my problem went away. I suspect that
there was corrosion or wear or a microscopic piece of crap in one of those itty
bitty orifices, or something. Never knew exactly what the problem was, but i
knew what the problem wasn't!

Final note: Does the $400 for the weber include the adapter plate and air
filter? You'll need to buy or make one. You will also need to cut the round
lead thingy off the end of the throttle cable (buy a spare so you can switch
back and forth) since the weber uses a screw clamp w/washer.

BTW if all you are doing is swapping the carb (Weber or stock) and aren't
changing anything else i.e. pollution control, stock manifold, etc, you won't
see that much improvement in power.

The single biggest improvement in horsepower on these engines comes from adding
the header! The best header IMO was the original Mugen Tri-Y especially for
Solo (very good low end and midrange power). You probably can't find one unless
you check e-bay and fine a good used one.

Otherwise the DC Sports unit is a quality unit. You will need to switch to an
Si oil pan in order to make it fit (the pan is a direct bolt on replacement).
There are other headers out there (4-1 as well as tri-Y). A 4-1 will make more
peak power but at a narrower power band. The tri-Y is better for Solo. You
don't have to change the float settings from stock. I suggested changing the
floats since they tend to stick and act up when they get old. Ditto on the
power valve. After changing, just follow the shop manual and set the level to
stock settings i.e. fuel level centered between the lines of the float bowl





The basic mods are to remove all of the choke plates and linkages etc. This
provides less restriction. (it will also make the carb very difficult to start
in cold weather! This isn't a problem when racing in the summer). Take the
guts out of the fuel evaporation chamber and make a blanking plate. Note - Once
you do this you may have to crank the car over for several seconds if it sits
for a long period in order to refill the float bowl. Remove the anti-run on
solenoid and snip the head of the pin off and replace, or remove the solenoid
and plug the hole with a screw and some JB weld. Plug all the vacuum lines to
the carb. Seal them with silicone. Check them every season since they can get
brittle and develope cracks. Get (make) some slightly richer jets for the
primaries. If you don't know how, contact Rivergate/OPM and see if they will
sell you just the jets. This will give you more top end power and won't hurt
the drivability at all. You may get some loud 'pops' i.e. real race car noises
from the exhaust when you close the throttle at high RPM (since you have removed
the pollution controls) but this won't hurt anything. The drivability of the
stock carb is great! Especially in the rain! Throttle response is excellent!

Change to a K&N filter. There is one element that fits the stock housing, and
there supposedly a different (slightly taller) element from earlier (83??)
Civics that will fit the stock housing if you remove the large rubber seal from
the bottom of the housing. The part number is different by one digit.

Get rid of the screen mesh cover over the carb. Knock the guts out of the
bimetalic valve that is built in to the air cleaner assembly for the incoming
air (pollution control) and block off the duct for hot air. Keep the stock cold
air intake since it draws air from the front of the car (near the headlights).

Route the vent line from the valve cover and PCV valves into a catch tank. You
must block off the opening created in the filter housing.

Don't ever, ever, ever futz with that small painted screw on the third
(prechamber) barrel!!!! There is nothing in the manual to describe what it
does, but if you mess with it, the car will run like crap!

Helpful tip...Your car has two fuel filters. One located after the fuel pump
(easy to get at) and one that's a royal pain to get at near the fuel tank.
Remove the fuel tank filter and replace with a piece of hose. Relocate that
filter to the engine compartment. I just cut the rubber line where it exits the
firewall and put the filter in-line there where it is easy to service. It just
hangs from the rubber hose but you can tilt the filter to inspect/change. Some
people might suggest just leaving the filter out completely, but filters are
cheap insurance. Just change them at the beginning of each season.




Use high temperature RTV to 'glue' the vacuum caps on. The main reason is to
prevent the caps from blowing off if the
car backfires. If you loose a cap, you'll
have a vacuum leak. The RTV is
precautionary.

The choke mechanism are the first set of plates you see when you stare down the
barrels. They are controlled by a bimetallic thingy on the side. Its black,
about an 1.5 inches in diameter, held on by three rivets or tamperproof screws.
Just drill out the rivets and take the guts out. Take the choke plates &
linkages off. When you are done, the only thing remaining are the three barrel
throttle plates and the accelerator pump. When you operate the throttle
linkage, you'll see all three plates open and closed.

The power valve is the small brass thingy located in the bottom of the float
bowl with the small pin sticking out. There is a corresponding spring loaded
pin on the upper half of the carb that pushes down on the pin. Use a small
(8mm??) thin wall socket to remove the valve. It has a small o-ring at the
base. Clean this passage out with carb cleaner and shop air before installing
the new valve.

Your gas mileage won't suffer too bad. You might loose 1 or 2 MPG, but that
will probably be from having too much fun with the new set up

The car will be very rough when it is warming up. Mine doesn't smooth out until
the water temp reaches about 160.

Cold starting is a bit of a pain without the choke. I usually give the gas
pedal one pump to squirt some gas and then crankover. When it catches it
usually dies right away. Give the pedal one more pump and crank again. When it
catches a second time, give the gas pedal some very fast 'taps' i.e. 1/4 pedal
travel pumps as fast as you can. This causes the accelerator pump to continue
to add a slight amount of fuel to 'richen' the mixture. If you try and hold
constant throttle, it will die cuz the mixture isn't rich enough for cold
conditions. After about 10-15 seconds, you should be able to stop tapping and
hold the throttle to maintain about 2000rpm to let the engine warm up. Let it
idle for about 30 seconds and then drive away, taking it easy until the engine
is warm.
"If Honda does not race there is no Honda." -Soichiro Honda

Posted Image

#2
eldo

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Good find CRXfanatic. I fully agree with Greg on how well the stock carb can perform. I am hesitating on throwing on a set of 1100 cc bike carbs because the modified stock one is running so smooth . It has been really easy tuning that carb for a cam and headers setup, 116 shot of nitrous and now with the T-25 @ 13 lbs. boost.
Ed
86 Crx DX EW3 block EW2 ported head , Coltcams (nitrous/turbo Stage 2 Triflow )

T-25 with a blowthrough Keihin carb - 13 psi .

I'ma in the Carburetion Nation

#3
StukThrtl

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"Don't ever, ever, ever futz with that small painted screw on the third
(prechamber) barrel!!!! There is nothing in the manual to describe what it
does, but if you mess with it, the car will run like crap!"

Wich one is this? I have a feeling i have futzed with it .. :/

#4
badpenny

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QUOTE (StukThrtl @ May 17 2007, 10:19 AM) <{POST_SNAPBACK}>
"Don't ever, ever, ever futz with that small painted screw on the third
(prechamber) barrel!!!! There is nothing in the manual to describe what it
does, but if you mess with it, the car will run like crap!"

Wich one is this? I have a feeling i have futzed with it .. :/

Remove your air cleaner assembly (the big thing with the filter in it)
If you are standing in front of your car, it will be located directly behind the intake ports (butterfly valves) You can't miss it, it has a big yellow glop of paint on it. Turning this screw to tight will bust the O-ring in it, causing fuel to shoot out of it and the potential of losing that screw (IIRC its a flat head) If you loosen it to much, you run the potential of fuel shooting out and loosing the screw, also, the potential to make your car a fireball is increased 10 fold.


Can someone post up a pictoral of everything described in this article?
Honda, because it's hard to look baller in your mom's Volvo.Posted Image 
The entire tool selection at Sears or the contents of a Snap-On truck will do you no good if you do not know how to use them.

#5
StukThrtl

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QUOTE (badpenny @ May 17 2007, 12:35 PM) <{POST_SNAPBACK}>
Remove your air cleaner assembly (the big thing with the filter in it)
If you are standing in front of your car, it will be located directly behind the intake ports (butterfly valves) You can't miss it, it has a big yellow glop of paint on it. Turning this screw to tight will bust the O-ring in it, causing fuel to shoot out of it and the potential of losing that screw (IIRC its a flat head) If you loosen it to much, you run the potential of fuel shooting out and loosing the screw, also, the potential to make your car a fireball is increased 10 fold.
Can someone post up a pictoral of everything described in this article?


I see it now. Haven't touched it. Bought this 87 hf from a friend and he had sold the carb off it. So i had to run all the hoses myself (vac diagram isn't quite correct for the carb i got) finally got it running good now though. Just tweaking to get past HC tests smile.gif

#6
86punishment

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QUOTE (StukThrtl @ May 19 2007, 03:48 PM) <{POST_SNAPBACK}>
I see it now. Haven't touched it. Bought this 87 hf from a friend and he had sold the carb off it. So i had to run all the hoses myself (vac diagram isn't quite correct for the carb i got) finally got it running good now though. Just tweaking to get past HC tests smile.gif



yea i effed with mine and could'nt get it to stay running below 3 grand ohmy.gif

#7
86rustbox

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re: "Get (make) some slightly richer jets for the
primaries. If you don't know how, contact Rivergate/OPM and see if they will
sell you just the jets. This will give you more top end power and won't hurt
the drivability at all."

i'm new to this forum...and wow...it's the most informative i've found so far. i'm debating weber/stock, but if all these things can be moded on it, i'll stay stock (cheaper too). i can handle most everthing except making slightly bigger jets. can anyone give me some tips on how to do this?

oh, and if anyone catches this auction in the next ten hours, i found these dual mikunis, although i can't afford them right now:

http://cgi.ebay.com/...em=160295564390


Edited by 86rustbox, 03 November 2008 - 08:00 PM.

beer is good for you.

#8
old skooler hatch

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if your talking about the big srew smack dab on the top its, the fuel pressure reg on the carb which controls where the float sits mine leaked when i messed with it just stuck a block off cap on it
one im not sure on is the screw for the 3rd bbl, turning it out makes the engine spudder and turning it in makes it bog and way too rich when wide open ive been trying to find the perfect spot but unsucessful
yet my idle screw is all the way in, idle will drop to 400 and go up to 1600 (ive got the vac idle raiser hooked up to the main vac on the intake) and other times with not even touching the screws it will idle at 2500 and slowly drop to 2000 im running no choke plate, no air cleaner and of course its devaced
o and i was wondering how easy is it to turbo carbs haha im kind of tempted

Edited by old skooler hatch, 04 September 2010 - 03:52 AM.

pshht ac haha power steering haha who needs it!

#9
letank

"Don't ever, ever, ever futz with that small painted screw on the third
(prechamber) barrel!!!! There is nothing in the manual to describe what it
does, but if you mess with it, the car will run like crap!"

Wich one is this? I have a feeling i have futzed with it .. :/

 

This one

 

CarbFulfltrHondaCv.jpg

 

from there

 

InletfilterUnit.JPG

 

it is the painted screw

 

CarbfulfilrScrw.jpg



#10
shuttlecraft

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CRXfanatic was talking about the lambda screw, also painted, usually yellow by the factory, which controls the ratio of throttle opening between the primary and auxiliary throttle plates.  I'll discuss that at some time later.  He is correct that the FSM makes no reference to it's adjustment, in fact I don't even think it's identified.  I'll have to look.  Anyway the FSM does discuss the float level adjustment screw shown in the above images and recommends slow 1/4 incremental turns if necessary.  These o-rings are extremely delicate and will easily tear.  Also the walls that these rings seal against get pitted (thanks to ethanol) and further compromises the seal.  If the float is functioning as it should as seen through the side glass, then yes, it is best to leave it alone.  If you're rebuilding the carb using a good quality rebuild kit, it will contain these metric o-rings.  And when I've installed them, I've have use a small amount of lubricant so that they will glide easily during the initial adjustment.  I've been on hunt for finding some outside of a rebuild kit because the kit is so expensive.  No luck yet but will post it when that happens.