Jalopnik
Back in the days of carbureted and plentiful used Plymouth Satellites, B-52's frontman Fred sang of the devil in his car. Beehive sporting singer Kate did Fred one better by wailing that she had the devil in her CAR-buretor! Having Beelzebub in the float bowl and demons clogging the jets is not a good thing at all. A carburetor rebuild can help exorcise evil spirits.
Hey, Bernoulli - Take it Easy!
The carburetor is one of those automobile parts of yesteryear still sworn by and at today. Like a modern electronic fuel injection system, the carburetor's main job is to meter fuel into the air entering the engine based on demand. Before modern multipoint electronic fuel injection became commonplace, the carburetor was the automotive king of mixing fuel and air. The carburetor mixes up fuel and air using Bernoulli's principle by way of a venturi. Bernoulli stated that air becomes less dense the faster it moves. As air moves through the throat of the carburetor, the vacuum created draws fuel into the air to in theory, produce the ideal fuel-air mixture based on engine demand. The carburetor venturi amplifies this effect by squeezing the incoming air into a tighter space, increasing velocity, and vacuum, and so on.
Simple, Right?
The carburetor mixes fuel into the air based on a near-ancient idea of a throttle cable connected to the loud pedal. The throttle plate meters air into the air pump that is the engine. If all goes well the carburetor sends the right amount of fuel to match demand. While multipoint fuel injection mixes the ideal amount of air and fuel together by way of various electronic sensors and a digital computer, the carburetor achieves this same task mechanically. The carburetor is a liquid analog computer. The carburetor uses a myriad of channels, passages, needles and seats, holes, check balls, and vacuum diaphragms instead of ones and zeros.
Mixed Nuts
The devil is in the details. Anything with that many moving parts is bound to be a bit of a cantankerous device. The maze of snakelike vacuum tubes and sensors can paralyze even the initiated. Adding to the operating complexity of a carburetor is that it is bolted down to the top or the side of a perpetually shaking engine that goes from stone cold to two hundred plus degrees and back again all the time. Fuel leftover when the vehicle is turned off combined with engine heat conspires to gum up the works. Evaporating fuel leaves a legacy of varnish and glue.
Ships in a Bottle
Anyone who ever spent any time building models as a kid can rebuild a carburetor. Those of you who relish putting ships in a bottle, or that have a Apple 5300c connected to a car battery running the garage security system might even be able to wrestle a dreaded feedback carburetor back into useful service. The other trick is to get the right rebuild kit. The fusty old Aisin carburetor show here had almost a dozen kits available for the different versions Toyota bolted into the Starlet. Safety first! Gasoline is flammable. Always disconnect the battery and have an approved fire extinguisher nearby before beginning any work involving gasoline or other flammable fuels.
Stuff You'll Need:
· A Crusty Carburetor
· A Carburetor Rebuild Kit
· About Four Hours
· Hand Tools, Including Wicked Small Stuff
· Large Tray to Catch Check Balls and Clips
· Gunk®, Chem-Dip®, or similar
· Gloves and Goggles
Remove the air cleaner. Mark all hoses and connections for future reference because you won't remember. Replace any cracked or broken lines. Remove fuel line using a line wrench to prevent stripped nuts. Use a rag or metal cup to catch any fuel. Remove the carburetor and put a clean rag over the hole.
Move to the bench. Now is a great time to take a digital image of the carburetor for later reference. Break down only the parts that need to be taken apart. Try to keep linkages and levers whole if possible.
Lift off the top of the carburetor to reveal the accelerator pump, and float. Don't tip anything upside down, or a dozen different size ball bearings and check valves will fall out.
If the main jets need to be removed use a screwdriver that fills the screw slot. Any nicks or scratches in the jets can alter the flow of fuel.
The key to any successful carburetor rebuild is the dip. Bailing wire comes in handy for fishing out parts. Small parts go into included dipping basket. Don't leave aluminum in there too long.
The accelerator pump squirts fuel into the throttle bore when you hit the gas. Soak the leather in a little oil to soften it up before installing.
Set the float level and drop by bending tabs and measuring. Do it again, and again, and again until it's right. Float drop and level has great effect on carburetor operation.
This little bugger controls the idle fuel mixture. Make sure it's not worn out or mangled, and that the air passages feeding it are open. Turn the screw until it seats, then turn out according to the instructions.
New gaskets are the key to proper sealing. Set the throttle plate stop angle on the primary and secondary throttle blades. Some rebuild kits come with cardboard templates to make this easy. This kit did not. We had to bust out the protractor and make cardboard templates.
Put it all back together. Easy right? Don't forget to inspect fuel for rust and crud, and install a new fuel filter if required before bolting it back up. Tighten mounting bolts in a criss-cross pattern. Do not overtighten! The carburetor will warp.
Comments
Told my girl I'd have to forget her
So I could buy me a new carburetor
RIP Freddie
Caburetor? Is that located near the blinker fluid reservoir?
I love you carburetory skillz. Your spelling, not so much. x-D
Remember kids...after you exorcise the evil spirits (thanks to the carb rebuild), it's time to exercise your ride!
@mytdawg: He's dead?
The smell of Carb Dip will stay with you for weeks. That stuff scares me.
Yea! The parts trailing guy is back!!
I quit messing with carbs a few years ago when that Atkins diet came out.
Come on, we needed one lame joke about it...the elephant in the room was starting to stink.
when i need to make one-off gaskets, i use some stamp ink from the wife's crafts and coat the soon-to-be-gasketed surface in it.
stamp it onto the gasket material and cut away.
quick and dirty, did this on the road once using a permanent marker and a sheet of plumbing gasket material as well.
Rebuild Carb
Step 1. Drop off at shop.
Step 2. Pick up at shop.
To many small pieces for me to tackle.
@SwatLax: Yeah, and it wasn't from lovin' his car...
Someday I will have to do this. I have at least two cars in deep storage that will likely need it when they come out again. I'll always be afraid of screwing up, but I also won't feel like a whole person until I do it.
Man, if you're going to tear one apart, at least use something more interesting than an old Aisin 2-BBL. How 'bout a Carter AVS 4-BBL off a '69 440?? Then you can talk about getting the spring tension set right so the back two gas spillers open at just the right time. Stepped needles and jets, anyone???
@Buckster: I'm with you. Normally, I'm all about doing stuff yourself, but carbs and watches are two things I'll leave to the experts (usually really cranky old guys in small shops with weird small tools).
When I was a tire monkey years ago, they had me run a carb over to "specialty rebuild shop." It was this old dude in his tool shed in his back yard. Outside was a pile of carbs 8 feet across and 6 feet tall.
If you have an extra spring or screw left over, and the car runs, don't worry about it. You've improved the design. Nissan could have saved money if they'd just talked to you first!
@Buckster:
The list has to be adjusted a bit for those fine, fine '70s SU carbs with the "auto" choke:
Step 1: Drop off at shop
Step 2: Accept phone call from tech marveling at your carbs' ability to eat parts
Step 3: Spend the next two weeks walking to the bar
Step 4: Pick up at shop
Step 5: Return to shop immediately
@Buckster, @Mad_Science: Or, for the opposite perspective, how about this:
1. Remove carburetor.
2. Install fuel injection setup.
Weeks of work, but it'll be worth it.
@JohnnyWagon:
PROTIP:
There are in excess of 4 accepted "correct" spellings for the full name of a carby.
When I was 17 and wholly unaware of my utter lack of mechanical inclinations, I decided to rebuild the quartet of carbs from my Hurricane 600. Needless to say, that was the last time I ever rode that bike. The worst part was, the bike ran perfectly before my dumb ass decided to tackle that project, and I still don't remember why I thought it was a good idea.
@eldo500: Hmmm... when I was pup and had no fear of the unknown, I did the carbs on my KZ1000, the SU's on my P6, the 2bbl Carter on my Chevelle. All just using whatever kit the auto/bike store sold me and a little dead reckoning; din't have no stinking manuals. I did carefully note the position (how many turns) of each adjustable adjustment screw prior to disassembly.
The Chevy carb was by far the most complicated. The SU's are remarkable for their lack of moving parts. They are little bitches to get a pair (let alone 3 or more) working in sync, however. Even with the special tuning tool.
@eldo500: I tried to rebuild the 4 carbs in my XS1100. Multiple carbs should not be attempted by people with limited skills. It took me about 5 minutes to break one, snapped the tower that held the floats right off.
I had to go hand it over to a mechanic that repaired it with a tiny drill and safety wire. It was a thing of beauty as repairs go.
He made me promise to never work on the carb bank again.
@b.borrman: UGH, the demonic SU carburetor... once had a lovely 66 Volvo P1800s. Was a dream to drive (I hear). Got it for a song, just needed a simple axle bearing. Granted, it took 3 weeks to get the damn thing - they had to get it from Sweden, though the part was made in Canada - but was simple to install.
However, I could never get the twin SU's to sync, no matter how many chickens were sacrificed at full moon, etc etc.
Decided that my car-ma was at fault; sold car for a profit (!) and the new owner loves it, drives it like crazy, no problem.
There's voodoo in them there carbs.. after all, SU stands for Satanic & Useless, right?
Mmm, carbs. I haven't even barely touched my 4 lovely Keihins on my CB550F. Should be the same thing, right? Guys?
@b.borrman: Nice! I'll probably just end up cheapening out and doing that instead.
Two of my rides use carbs, and one's from 1945 - though to be fair, that one just about amounts to a pipe with a hole in it, and a hose from the gas tank is plumbed to the hole.
I did a full carb rebuild on an Opel GT. There were about as many moving parts in that one thing a there were in the entire engine. We also found one of the check valve beads that had been lost from a previous rebuild - it was in the float bowl.
Word to the wise: do your rebuild on a jelly roll pan - the biggest one you can find. Anything tiny that jumps out will roll much farther than you ever imagined. The jelly roll pan has edges that will stop little parts.
It's a bad idea to use Sweetie's favorite pan. Don't ask how I know this.
Reminds me of a carb-related Henny Youngman riff...
I came home from work. My wife met me at the door.
She said, "Honey, there's something wrong with the car"
"What's wrong?"
"I think there's water in the carburetor"
"Where's the car now?"
"In the lake"
Comment on this post
Reply by EmailLogin with your username and password below. Or comment on this post via email.
Forgot your username or password? New User?