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 headache and sweat.
Carbs come in many shapes and sizes. Single 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, AirPods Pro Case and the process of cleaning those components is generally identical.
BEFORE YOU START
Make sure that dirty carbs are actually 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 article eventually 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 determined 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 manifold 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 single 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 create as much space as possible 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 straight backwards nice and easy, but that is pretty rare. I usually end up rotating them up then rotating them down as best I can while pulling backwards furiously. This can really take some work and time, especially if you’ve never done it before. In real extreme cases where you simple can’t get the carbs to pull backwards out of the manifold boots I have a couple tips. These tips should only be used in extremely difficult cases when you have been struggling for an hour and simple can’t get the carbs to pull backwards out of the manifold 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 garage floor and the carbs aren’t budging. Wrap a ratchet strap around one of the outer carbs and put the hooks somewhere on the rear of the frame. Then slowly ratchet the carbs right out of the boots. Be careful 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 method above. Sit down on your butt along one side of the bike. Wedge one of your feet up between 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 couple 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 corner 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 obvious 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 generally a good idea to drench everything in carb cleaner (available at any autoparts store). Sometimes the pins will practically fall right out, sometimes they’ll be so stubborn you won’t think they’ll ever come free. But they will! Carefully push on the pin from either side. Sometimes a nail and a gentle 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 really stuck and you can’t seem to work them free here are a couple tips.
Tip 1: Heat – Adding a little flame to the float pin towers can help. **Don’t Burn Down Your Garage!!**
Tip 2: Pliers – Using pliers to gently clamp the end of the pin and push it 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 everything aside. Next remove the main jet, pilot jet, and idle jet (if there is one). They should come out easily 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 gently pull the slides up out of the carburetor body. You can gently pull on the rubber diaphrams, but be very careful not to tear them. If they don’t come up easily stick your finger into the carb intake and push the slide up with your finger. You can also gently pry it with a screw driver (gently). If it doesn’t want to budge don’t force it. Instead finish reading this article and pay attention to the boiling tips further down.
Now your carbs should be pretty well emptied out. If the throttle on the bike moved fluidly and smooth there is little reason to do much to the carb bodies themselves. However, if the trottle was real sticky or frozen 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 generally try to break racks of carbs apart. It isn’t often necessary and can be confusing to put everything back together in the right places. Also, the little 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 smooth 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 through it. The idle and/or pilot jets have extremely small holes so make sure you are looking through them straight. If you can see through the jet it isn’t clogged. There could be a little gunk built up around the edges so spray them down with carb cleaner and let them sit a bit.
If you can’t see 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 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 thought carb cleaner would be the magic answer. It isn’t. In fact, I hardly ever use carb cleaner any more, because it simply doesn’t do a very good job of anything but removing varnish from the bowl and slide. But try this.
Poking it through. – Collect 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 gently try to poke it 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 around for a couple minutes. When you pull them out blow some compressed air through them and you’ll most likely be good to go.