I get asked about Carburetor Cleaning regularly both from readers and from friends offline. So I've decided to write a definitive guide for cleaning carbs the Right way. So put your tools down for a minute, grab a beer, and give this a read. You might just save yourself a lot of ill and sweat.
Carbs come in many shapes and sizes. Singular carbs, dual carbs, racks of 3, 4 or 6, V racks, carbs with ticklers, carbs with accelerators, carbs with asynchronous designs, and carbs that operate vertically. While working on some carburetors is more difficult (due to design) than others, they all share the same basic components, and the process of cleaning those components is commonly identical.
Before You Start
Make sure that dirty carbs are for real your problem. Lots of things can make a bike run poorly or not start. Weak battery, corroded electrics, old spark plugs, bad timing, low compression, mis-adjusted valves, dirty air filter, and plugged exhausts can all cause poor running. I'll write an record finally on how to diagnose poor running conditions shortly, but for now - lets just deal with the carbs.
Ok, So Your Carbs Are Dirty
Once it has been considered that the carbs are the problem it's time to get to it. Some racks of carbs are easier to remove than others. If you're working on a newer model bike the rubber boots from the airbox to the carbs and the multiple boots from the carbs to the motor should be relatively soft and pliable. On older bikes however this is rarely the case.
First remove the fuel tank, seat, and side covers. Depending on your model of bike other parts may need to be removed too. For many Singular cylinder bikes the carb can often be removed without removing any body work at all.
The bike below is a 1983 Yamaha Xj750 Seca with 4 inline Hitachi carburetors
You'll want to loosen the circle clamps on all of the rubber boots. Sometimes I'll even take them all right off (carefully, without bending them too badly) so that they aren't in the way.
Inspect the airbox. On many bikes it is bolted in place to tabs on the frame. remove those bolts and try to generate as much space as inherent for the airbox to pull backwards.
Next, put the bike on it's centerstand and straddle it facing forward. Put your right hand on the right-most carburetor and your left hand on the left-most carburetor and get ready to sweat. Sometimes you'll be able to pull the carbs level backwards nice and easy, but that is pretty rare. I regularly end up rotating them up then rotating them down as best I can while pulling backwards furiously. This can for real take some work and time, especially if you've never done it before. In real greatest cases where you straightforward can't get the carbs to pull backwards out of the multiple boots I have a join tips. These tips should only be used in highly difficult cases when you have been struggling for an hour and straightforward can't get the carbs to pull backwards out of the multiple boots.
Tip 1: Ratchet Straps - This is sort of a last resort, but it has worked without fail for me when I'm pooling sweat on the stable floor and the carbs aren't budging. Wrap a ratchet strap nearby one of the outer carbs and put the hooks somewhere on the rear of the frame. Then gradually ratchet the carbs right out of the boots. Be meticulous not to pull them too cockeye'd or you could damage the boots. Attach a second ratchet strap to the other side if necessary. (Note: you can do this in the opposite direction to force carbs back into the boots once they are clean.)
Tip 2: Full Pull! - You should do this before you do the ratchet strap recipe above. Sit down on your butt along one side of the bike. Wedge one of your feet up in the middle of the forks and the front fender, then put both hands on the same outermost carb and Pull Pull Pull! This might not work so well if you're short! Ha.
Ok, So The Carbs are pulled back
Chances are the airbox boots are all crammed up now. Do your best to rotate the carbs up and out from the boots and pull them out one side of the bike. Sometimes it's easier to pull the carbs out one side than the other, so have a look to see if there are frame elements, motor elements, or hoses that may block the carbs from coming out on one side.
Also keep note of the throttle cable(s) and choke cable (if there is one). Now may be a good time to loosen the nuts that hold them in place and disconnect them.
Struggle just a join more minutes wriggling the carbs out the side.
Ok, You have the carbs off the bike
Make sure you brush off any loose dirt or grime, then flip the carbs over and remove the screws from the corners of the carburetor. Some carbs won't have bolts in the angle and instead have a wire latch over top which can just be forced over.
Remove the bowls.
If the carbs are real gummed up the insides might look like this:
It's clear that these carbs are all clogged up. Some carbs might not look so bad, some might be a lot worse. It's always a mystery what will be inside the bowls.
Now it's time to remove the floats. It's commonly a good idea to drench all in carb cleaner (available at any autoparts store). Sometimes the pins will roughly fall right out, sometimes they'll be so stubborn you won't think they'll ever come free. But they will! considered push on the pin from either side. Sometimes a nail and a diplomatic tap from a hammer is helpful. **Be Careful**, using force to remove a stuck float pin can break off the pin tower. If they are for real stuck and you can't seem to work them free here are a join tips.
Tip 1: Heat - Adding a exiguous flame to the float pin towers can help. **Don't Burn Down Your Garage!!**
Tip 2: forceps - Using forceps to gradually clamp the end of the pin and push it straight through has worked well for me in the past. **Don't break the towers!!**
Once the float pin is out you can remove the floats, the float needle, and unscrew the float jet screen.
Set all aside. Next remove the main jet, pilot jet, and idle jet (if there is one). They should come out for real with a flathead screw driver.
Set them aside.
Next flip the carburetors back over and remove the caps. Underneath the caps is a rubber diaphram with a spring. Sometimes the caps have a tendency to shoot off the top, so be very methodical when removing the screws. Other times the cap tends to stick down until you start to pry at it, then it shoots off, again, just be cautious and don't loose any parts.
Next you'll want to gradually pull the slides up out of the carburetor body. You can gradually pull on the rubber diaphrams, but be very meticulous not to tear them. If they don't come up for real stick your finger into the carb intake and push the slide up with your finger. You can also gradually pry it with a screw driver (gently). If it doesn't want to budge don't force it. Instead close reading this record and pay concentration to the boiling tips further down.
Now your carbs should be pretty well emptied out. If the throttle on the bike moved fluidly and flat there is exiguous conjecture to do much to the carb bodies themselves. However, if the trottle was real sticky or freezing there are a few things you can do to free it up. Sometimes just drenching all the throttle components on the carbs and letting it soak is enough, other times it is not. I commonly try to break racks of carbs apart. It isn't often needful and can be confusing to put all back together in the right places. Also, the exiguous rubber connector hoses and o-rings have a tendency to crack or leak if you mess with them. If you can't work the throttle back and forth until its flat have a look at the boiling tips further down.
Keep it Neat
Organization pays off.
Clean the Main, Idle and Pilot Jets
Hold each jet up to the light and see if you can look straight through it. The idle and/or pilot jets have highly small holes so make sure you are seeing straight through them straight. If you can see straight through the jet it isn't clogged. There could be a exiguous gunk built up nearby the edges so spray them down with carb cleaner and let them sit a bit.
If you can't see straight through the jet it is clogged and needs to be cleaned. always try the easiest things first. Here's an ordered list of a few things you can do to clean the jet.
Blow straight through it. - Rarely works, but hey, who knows.
Compressed air. - Force 100 pounds into it. Works occasionally. Make sure to hold the jet tightly so it doesn't go flying across the garage. You might put the jet back into the carb body to hold it in place for this.
Soak it in cleaner. - When I first started cleaning carbs I idea carb cleaner would be the magic answer. It isn't. In fact, I hardly ever use carb cleaner any more, because it plainly doesn't do a very good job of whatever but removing varnish from the bowl and slide. But try this.
Poking it through. - derive a few different diameters of needle like objects. A wire from a steel bristle brush works well, a bristle from a broom works well, a baby pin, small sewing needle, etc. Very gradually try to poke it straight through the jet. If you are using a metal needle use caution, brass jets can scratch and deform easily.
Boiling! - This works better than anything. Toss the jets into a pot of boiling water and let them bounce nearby for a join minutes. When you pull them out blow some compressed air straight through them and you'll most likely be good to go.
Some idle jets can be real tricky and never seem like they'll be cleaned out . . . Just keep working at it, I've never met a jet that couldn't be cleaned.
Cleaning the Choke and Air mixture Screw
Air mixture screws have a tendency to strip or break. If the carbs were real gummed up you might find that the air screws are stuck. Don't force them, if they don't want to come out, just leave them for now. It is fairly rare that these screws will need to be cleaned because they are above the float level. If you can get them out just wipe them down with carb cleaner and spray some straight through the jet.
Cleaning the Slide and Needle
These are easy to clean. Squirt them with a bit of carb cleaner, wd-40, or whatever similar, then wipe them down with a rag. Once the varnish is gone they're good to go. Sometimes they get heavy varnish on them which I will scratch off considered with a piece of plastic. Scratching the slide and needle is a Bad thing, use caution.
Cleaning the Carb Bodies
Use the same squirt and wipe recipe noted above. Most of the time the other pressed jets and passages in the carburetors won't be clogged. But if the bike has been sitting a real long time with squirrels in the airbox it is for real possible. Us a compressor to blow some air into every tube you can see. Listen for the air coming out the other side. If no air compressor is ready use a can of Wd-40 with a straw attachment.
If some of the pressed jets are clogged it can be difficult to open them up. There are a few things you can do.
Carb Dip - Most autoparts shop sell carb dip. It comes in a can similar to a paint can and is a Very harsh cleaning agent. Soak the whole carbs in this dip. This dip can eat at rubber and plastics if they are submerged for too long, so try and remove all you can from the carb bodies before soaking them. Once you pull them out swish the carbs nearby in a bucket of water to clean off the excess dip, then hose them down with Wd-40 to get rid of the water.
Boiling in Water - Not many population do this but it is by far the best way of cleaning carburetors. Dropping the carbs into a pot of boiling water will instantly free up stuck slides, throttle plates, and other freezing parts. It will also loosen the dirt and grime clogging up pressed jets and other passages. Just make sure to dry the carbs wholly with compressed air or the sun afterwards.
Boiling in Lemon Juice - There is Nothing better at cleaning carbs than a giant pot of boiling lemon juice. The acidity from the lemons eats straight through everything; gas varnish, oil build up, dirt, grime, etc. Sometimes I won't even bother doing whatever but this - I'll just remove the bowls, remove the caps, then drop all into the pot and let it sit for 20 minutes (rotate them a few times). The one caveat to doing this is that you'll want to wash the lemon juice off the carbs as soon as you pull them out. So have a bucket of water ready, or a can of Wd-40 to hose them down. Also note that the acidity has a tendency to put a dull close on the aluminum bodies of the carbs. This isn't a problem in most cases, but if you must have all shiny be prepared to do a exiguous scrubbing and polishing afterwards. It may sound weird, but trust me, I just saved you Lots of time. (Most dollar shop sell 1/2 gallon jugs of lemon juice, so buying a few gallons will only cost you . Plus you can put it back into the bottles afterwards and save it for next time.)
Cleaning the Bowls
This is pretty level forward. Use any of the methods above to transform your varnished bowls.
Most carb bowls are simple, just clean them up and they are good to go. But I picked this Hitachi's for photos because they have a jet built into the bowl. You can see the 'fifth' hole along the edge of the bowl, that is for real a thin tube that extends to the lowest of the bowl. This is for the idle jet and is highly important. If these passages are clogged, the bike won't stay running, period. Use the same poke, soak, and boiling methods outlined elsewhere in this article. Not all bowls have these passages, only some, if your's don't - good for you!
Once all is Clean
Now that all is clean it's time to put it all back together. Take your time and make sure you put all back where it came from. Wd-40 is your friend. When screwing in the jets don't over do it, they only need to be seated and snug, do Not use any force putting the carbs back together.
If the bowl gaskets got goobered up you can put a exiguous Rvt on them. So long as the float needles are still in good health leaky gaskets shouldn't be an issue. However, economical carb tinkerers may want to order replacements if necessary.
Once the carbs are back together stuff them back into the bike!
Extra Notes
Rebuild Kits - This guide did not mention rebuild kits until now. Rebuild kits (consisting of new gaskets, jets, needles, etc) can be purchased for nearly any bike, both old and new. 95% of the time these are Not needed. I have rebuilt adequate carbs to block off main street, and only once have I used new parts. Once!
Carburetor Adjustment - Carburetor adjustment, setup, jetting, and synchronizing is a whole encyclopedia waiting to happen. Those topics are not covered in this article, but I will address them in hereafter articles.
Carburetor Polishing - External carb asthetics will be prominent to some, and not to others. Cleaning is all I am surface here, this will be addressed in the future.
Work Space - Make sure you have lots of space to keep organized. I also like to work on a wooden surface because it absorbs the spilled gas and cleaners rather than pooling.
That's it! You're Done!
I'll continue to write a join more linked articles about diagnosing carburetion issues as well as the permissible way to adjust, jet, and tune your carbs.
How to Clean a motorcycle Carburetor, The Right Way
