How to Clean Motorcycle Carburetors

This free motorcycle was sitting in David Durlach's garage for 20 years.

David eventually tired of it, and gave it to Prank, who cleaned out the brake lines and added a new battery. Then winter happened, and it sat in Deepest Darkest Somerville for a year, until prank graduated and moved to California, and I was given care of the motorcycle. I wheeled it back to MITERS to see if I could get it to work. A new battery, some carb cleaner, and a little bit of hope, and it started up! Yum, throaty rumble!

With visions of a cross-Cambridge joyride followed by summers of long-distance road trips, we took it to the road and kicked it into gear.

But, every time the gas was added from the gas tank, the 'cycle coughed up and died. Oh well.

I emailed the MIT Motorcycle and they said "clean the carbs". With a monkey wrench and a vague idea of what I was looking for, I did all of the following. Now they sparkle!

Step 1 Get the Float Bowl

There are some haaard to reach screws in there, man.

Get them all out, until the float bowl is in your hands.

Comments

[Ben.C123]

My bike has been sat in my grage for about 2 or 3 months and won't start. I've tested the spark plugs and they all wok and i've drained the tank and put fresh petrol in just to be safe as i've been told by a few people about petrol going bad. When i manually put fuel in the engine fires up but doesn't hold on to the power. Could this be my Carburetor? The fuel tap was on reserve, would this mean my petrol was constantly slowly dripping in which would cause the carb to get bunged up with sludge and gunk?

[suzukitard]

in some cases the fuel has corroded the lining in the carburetor and using a coarse material to remove the gunk can further remove this lining causing rust and thus ruining your engine
(IN SOME CASES!!)

[cmckay1]

I have that same bike and I'm working with a cleaner motor than what you've got there. I'd be surprised if it worked better after only cleaning the float bowl. Pulling the whole carb out takes about as much time as cleaning the jets with break cleaner.

[cparshley]

umm, this is great if you just want to clean the float chamber, but for an old bike which was mostly sitting, I would suggest pulling the whole carb off and giving everything a nice once over. Most of the problems from old gas tend to be clogged jets, and other parts which will not be cleaned simply by cleaning out the float chamber.

[discontinuuity]

So how are you going to go about registering with the DMV? Do you have the title from whoever gave you the bike?

[stasterisk]

No title for it a-tall. I'm not sure yet - I thought maybe I'd jump that ramp when I can drive up to it.

[skunkbait]

Alot of southern and western states are a little looser on the title part. See if you can find out who the last registered owner was, then apply for "lost title" in their name. In some states you can get salvage, builders, or bonded titles. If you have friends or family in one of those states, it won't be too hard. Good luck. I've owned a GS bikes. Change the oil regularly, turn the fuel "off" when parked, and it should last forever.

[xchef95x]

i have a 1978 gs750 and my fuel swithc say's " pri, on, res" which one should i set it to in storage...?

[jack8559]

turn the fuel off and run the engine out of gas - no varnish build up!

[xchef95x]

no fuel off... i guess with my model the air box was converted to pod filter (which is another mess in itself) but the air box had a vacuum to prevent the gas from leaking.... i have to figure out how to put the airbox back on now..... tried once this summer, but couldn't get it to fit with a 1/2 full tank on... hopefully i can drain it this weekend and then try this winter to put the airbox back on.

the person before me (a friend) took the airbox off for more power, but never rejetted just played around with the carbs for a 'better' air flow... i beleive putting the airbox back on will fix a ton of stuff.... or a re-jet.

thank you all

[jack8559]

Maybe you could install your very own on/off valve in the fuel line? Not sure how your line is routed, not familiar with the bike, OR you could just drain the tank and run the carb dry after that.... It just seems to be a surefire way to get it all out of the system and there will be no buildup since the fuel isn't there.

You could also look at it from another point of view too though - since there is no fuel there the seals might dry out and make the fuel system start leaking.

I guess maybe overall the best thing to do is to run the engine a half hour or so every month at LEAST to insure that everything stays varnish and leak free.

[xchef95x]

thanks for the info.. this bike is more work than play, but i love it. i make sure i run her all the time even for a couple minutes just to make sure. i also swear by Fuel Stabilizer now. i had a guy that was gonna check my bike out and fix it all nice, but he got into a terrible car/motorcycle accident and is still in the hospital. i work on the bike everyother weekend, the more i do the more i'm learning. but maybe i will try just installing an off valve?

[jack8559]

Running the bike for a few minutes a week and using fuel stabilizer is a great idea!
Make sure not to let it sit for over 4 or 5 months without running it. Gas these days isn't what it used to be - you may wind up having to drain the tank and putting fresh gas into it if the stabilizer doesn't do its job.
I think running it a few minutes a week will do the trick and never put too much gas in the tank, at least not more than you will burn in a week or so. Good Luck!

[J.C.1]

My book on my yamaha says on or reserve only lets gas pump thru carbs when motor is turning over or running.Prime lets gas flow constantly.So either on or reserve works.TO be safe I would drain gas from tank and carbs if storing for a long period.

[103curly]

I fiddled with the fuel system,res allows the fuel to flow,pri doesnt .Anyway I have a problem with my carbs,I believe I cleaned all the jets ,the bike has been sitting for quiet sometime.Itll start when I put fuel in the barrells manually,although it wont hold.

[skunkbait]

Hmmmm? I'd say there should be a fourth option. Disconnect the fuel line from the carb. Then try all the settings. If one of the settings doesn't let the fuel flow out, then go with that one. If you're just putting it in (warm, dry)storage for 4 or 5 months, it shouldn't be a problem anyway. Some folks would disagree with me, but if I were going to store it for a year or two, I'd run it completely out of gas. Or, you might just look into good fuel stabiliser, and keep the bike full.

[Rishnai]

How true. We've got some non-numbers matching seventy-year-old-plus machines hanging out at our place. We're hoping we can get some Colorado titles for 'em once we fix 'em up. Last registered in Arizona 30 years ago and the paper trail is sketchy, so hopefully the law isn't too picky here. The '39 probably has a half a million miles by now, just needs a ring job, but my dad had to park it since he couldn't afford that.

[Hoopajoo]

In Virginia, you can apply for a 'Title of Abandonment' or a 'Mechanic's Title'. These are used for instances where vehicles are abandoned at shops and garages. The owner disappears and the machinist is left holding the bill. I have gotten so many cars and bikes from garages that way. Usually takes about $30 and a couple of weeks while DMV researches the last owner through the VIN# and attempts to contact them.

[Rishnai]

I looked it up, and same here. "Lost title" and "mechanic's title" are both ways to get a new title on the books, depending on whether you (or whoever gave you the bike) lost the title, or it was a case of abandonment.

[renzow]

need Help here people, someone knows how to clean carburetor of a honda tmx 155 ??? never cleanse it yet w/in 2years.

[abadfart]

i would suggest pulling the carb off all the way and dunking it in carb cleaner and blowing out the jets with an air compressor and a ball needle with the tip cut off

[billyridge]

(Need Help) the carbs on my 81 yamaha are not acting right it has a four carb set up bike will idle when chock is on when bike is cold but when i take the chock off bike will not sit and idle also when reving motor bike has some bogging

[casy.ryback]

could you take a moment and help guide me in the right direction.
 
bike-  1982 LTD550 4CYL
 
DISASSEMBLED CARBS SOAKED FOR TWO DAYS IN CARB CLEANER.  PLACED IN A PAN OF HOT HOT WATER (NOT BUBBLING BOIL), USED CARB CLEANER AERSOL TO BLOW OUT ORFICES.  REASSEMBLED PUT ON BIKE WITH THE BACK OF THE CARBS OPEN (NOT IN AIR BOX).  GAVE IT A SHOT OF STARTING FLUID AND WALLA STARTED RIGHT UP.  WARMED UP AND SHUT CHOKES OFF.  IDLED PERFECT.  GAVE A FEW TWISTS OF THE THROTTLE AND RESPONDED NICELY.  PURRED LIKE A KITTEN.  DECIDED TO HOLD IT AT 4500 RPMS AND WITHIN TWO SECONDS THE CARBS BOGGED DOWN AND KILLED THE ENGINE.  NOW IT WILL ONLY RUN WITH THE CHOKE ON AND THE THROTTLE WIDE OPEN.  UNDER THIS CONDITION IT WILL RUN 2000RPM NOTHING MORE.  IF YOU TURN THE CHOKE OFF IT WILL NOT IDLE.    CHECKED THE FUEL LEVELS IN THE BOWLS AND ALL ARE AT APPROPRIATE LEVEL.
 
I DONT KNOW WHAT THE HECK HAPPENED. 
 
I PULLED THE CARBS DISSASSEMBLED THEM AND CURRENTLY HAVE THEM SOAKING.  I ALSO REMOVED THE FUEL AIR MIXTURE SCREWS.  THEY WERE EACH ABOUT 1 3/4 TURNS FROM BOTTOM.
 
WHAT ADVISE CAN YOU OFFER?

[HAL 9000]

The only advice I can offer is to find some forums dedicated to whatever bike you have, register, and ask your question there, but for the love of God, don't do it in all caps! I recently bought a disassembled Honda CB550, and I'm trying to get it running. Knowing almost nothing about motorcycles except that I want one, I found forums devoted to the old Honda SOHC 4-cylinders to be a wealth of information on everything from polishing and painting to rebuilding engines, to finding new and used parts for them. There must be forums for your bike, and they shouldn't be hard to find with Google. good luck.

[meff00]

 Also check if the gas is fresh. I was working on a bike once and I thought I had fresh fuel but it was last years stuff in the tank. Once I drained and refilled it ran great!!

[d1rage5]

if your carbs were sitting for a long time with gas in them (gas turns to varnish in 45 days) this most the time will not come off with just carb cleaner and soaking. the small holes do not get cleaned and fuel restricting is still happening.  One more thought did you completely disassemble the carbs (meaning remove all rubber rings)? if not the solvent based cleaners will destroy these rubber or felt rings and you will  or can have air leaks.

I do a carb service and do not use solvent based cleaners and special machine to clean.

[algarbonzo]

might sound stupid, but is your fuel petcock turned on all the way? plugged fuel lines?

[kerbang]

No way. If you don't lose parts from opening the float bowls upside down, you'll still have fuel leaking out everywhere from having blocked jets. The screws aren't hard to get to if you take out the carburetor. This'll get people in trouble if they're not careful.
http://ezinearticles.com/?How-to-Clean-a-Motorcycle-Carburetor,-The-Right-Way&id=1460030

[A-Nuke1979]

Trouble, indeed!  Some of the best advice I've received (and shared) regarding carbs is to take LOTS of pictures and notes of the disassembly, before and during.  It is hugely valuable to have those references to put everything back together correctly.  This goes for the hoses for fuel, air, vacuum, etc. on the outside of the carburetors, too!  Leftover parts are a bad thing.

[Chainsaw Monkey]

Someone may have already posted this, didn't read them all, but you could have avoided the build up of crud in your carbs during the winter months by simply adding a proper amount of fuel stabilizer before you stored the bike.

[d1rage5]

You need to remember that any gas product will turn start to varnish in 45 days and does not matter what additive you put in the gas it may help the time to maybe 55 to 60 days. this varnish is what makes a good carb go bad.

Carb4bikes.com is a site for carbs and repair that will have a forum that will go into detail, right now it is now all the way up in running due to a hosting coping going out of business and getting our domain name back and setting up from scratch (they have our backups as well).

[rkr]

Hmm, this instructable is okay, but, to my knowledge, the proper way to clean out a carburetor is to remove it completely, then use an air compressor to clean out the passageways, and maybe squirt a little carburetor cleaner into each of them. Because chances are, if you had junk at the bottom of the float bowl, then there could be some clogged passageways. This is simply a suggestion, not meant to spark debate.

[casy.ryback]

could you take a moment and help guide me in the right direction.
 
bike-  1982 LTD550 4CYL
 
DISASSEMBLED CARBS SOAKED FOR TWO DAYS IN CARB CLEANER.  PLACED IN A PAN OF HOT HOT WATER (NOT BUBBLING BOIL), USED CARB CLEANER AERSOL TO BLOW OUT ORFICES.  REASSEMBLED PUT ON BIKE WITH THE BACK OF THE CARBS OPEN (NOT IN AIR BOX).  GAVE IT A SHOT OF STARTING FLUID AND WALLA STARTED RIGHT UP.  WARMED UP AND SHUT CHOKES OFF.  IDLED PERFECT.  GAVE A FEW TWISTS OF THE THROTTLE AND RESPONDED NICELY.  PURRED LIKE A KITTEN.  DECIDED TO HOLD IT AT 4500 RPMS AND WITHIN TWO SECONDS THE CARBS BOGGED DOWN AND KILLED THE ENGINE.  NOW IT WILL ONLY RUN WITH THE CHOKE ON AND THE THROTTLE WIDE OPEN.  UNDER THIS CONDITION IT WILL RUN 2000RPM NOTHING MORE.  IF YOU TURN THE CHOKE OFF IT WILL NOT IDLE.    CHECKED THE FUEL LEVELS IN THE BOWLS AND ALL ARE AT APPROPRIATE LEVEL.
 
I DONT KNOW WHAT THE HECK HAPPENED. 
 
I PULLED THE CARBS DISSASSEMBLED THEM AND CURRENTLY HAVE THEM SOAKING.  I ALSO REMOVED THE FUEL AIR MIXTURE SCREWS.  THEY WERE EACH ABOUT 1 3/4 TURNS FROM BOTTOM.
 
WHAT ADVISE CAN YOU OFFER?

[rkr]

Sounds like you might have some junk in your gas tank, that's the only thing I can think of. I would advise cleaning it out as well.

[Mikel25]

Can you just add some gas treatment or fuel injector/carburator cleaner to the gas?

[saddlewarmer]

If you really want to get that Suzuki GS running visit www.thegsresources.com Lots of info there. I've got 3 Suzuki GS bikes

[stasterisk]

Awesome, thanks!

[xchef95x]

how's the bike now a year later? mine is a 78 gs750, and i love it.

[earz_cd]

You got lucky if just cleaning the bowls out helped the running condition. Most of the time, the varnish (brown gunk) will partially or completely clog one or more of the jets in one or all of the carbs. If a jet is clogged - fresh fuel can not be drawn through the jets to feed the cylinders - and you end up with a bike that runs poorly. On a lot of bikes, you cannot get all the float bowls with the carbs still on the bike. Ideally, you want to remove the entire carb assembly (the entire group - 1, 2, 3, 4, or 6 carbs depending on the bike). Once the carbs are off the bike - remove all the float bowls, jets, floats, float valves, slides, slide needles, etc. to inspect, clean, and possibly replace these parts. It's also a good idea to check for proper float height (fuel level) as it can also affect the running condition.

[kill-a-watt]

Carburetor 'eh? That's like vacuum tube technology.

Well if you are going to be fooling with carbs, you ought to know about the $1.98 tune-up. I just googled the term and while there are a few references, it looks like this trick might be going the way of the dodo.

I've used this trick to get carbureted vehicles to run right, and it's simple and downright amazing. Back in the day, I even tried it on some dude's jeep after he had a romp in the mud. It cured his "wouldn't idle" problem.

Here's how to do it:

1. Take off the air cleaner and start the engine

2. Rev up the engine about half way up.

3. Put something suitable over the air intake, cutting off all incoming air. Because of the air cleaning housing, this is usually a metal cup or something, but anything that will cut off air will work.

4. when the engine almost dies, remove the obstruction. Wash, rinse, repeat. (repeat 1 or 2 more times)

What is happening is that the momentum of the engine creates a strong vacuum in the carb. That vacuum dislodges minor specks of crud that are in the jets and stuff. Frequently, this little trick is all it takes to get an engine to idle correctly or accelerate smoothly.

Although in your case, with 20 years of idle time, it may be time for a proper rebuild kit.