Cleaning a Honda GX Carburetor

Welcome back to the RuggedMade Tech Corner. I'm Jared. We're continuing our series of videos on how to troubleshoot, maintain, and repair your lawn and garden engine. We're talking about these kinds of small engines that you would have on your log splitter or a plate compactor, snow blower, generator, these kinds of machines. So, in this episode, we're going to take a closer look at our carburetor. The scenario is: your engine isn't starting or it starts but it doesn't run right and you've narrowed it down to the carburetor as the likely culprit. Now, this assumes you've done all your routine maintenance and if you haven't done so already, be sure to watch our previous video where we go over a lot of general troubleshooting techniques. You can click the link here to watch that video.

Start by getting rid of all the fuel, and that means the fuel in the tank, in the fuel lines, and in the bowl of the carb. The easiest way to get that much fuel out, like if you have a half a tank or more, is a siphon hose or these very inexpensive electric fuel pumps actually work pretty well. And, we're assuming that you've already ruled out the possibility of bad gas being the cause of the engine not running right. If you haven't already done that, now's the time to check it with known good fuel and the best way to do that is to get some of this ethanol-free fuel from the hardware store. If it won't run on this stuff, it's definitely not a fuel problem.

What are the symptoms you're having? If the engine doesn't start at all, it's probably not getting any fuel. If it does start but it doesn't run right or it dies out after a while, well, the carb is clearly letting some fuel in but probably not enough. And, that could be due to some blockages in these tiny little passageways that run all through the inside of the carb. So, in either case, you're going to have to remove the carburetor and give it a good cleaning. We're going to be working on the carburetor from this Honda GX270 engine. This is representative of a lot of the engines in common use and is identical to the carburetor on the Raven engines. You might have an engine from Briggs or Kohler or Tecumseh and the carburetor might be a little bit different, but generally the techniques we'll be talking about today will still apply. So, refer to your owner's manual for more details.

Before you do a full tear down of the carburetor, you can easily check the float inside the bowl. If your engine seems to constantly flood or if it isn't getting any fuel, the float and the needle in the bowl may be the culprit. To remove the bowl, make sure the fuel petcock is in the off position and then we're going to remove the bolt at the bottom. So, here's our fuel petcock in the off position. This is the drain bolt. You probably want to drop that first and drain any fuel that may be in there from some testing you were doing. Then, we're going to remove this bolt in order to drop the bolt. It's a 10 millimeter head.

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And there is a gasket that you don't want to lose. A visual inspection will tell you a lot. If the bottom of the bowl is full of nasty green goo or whitish powder, you may want to jump right to replacing the carb because there could be lots of mystery goop deep inside the carb that you may never be able to clean out. But, it is often possible to bring a carb like that back to life and all it will cost you to find out is a bit of time.

Make sure the float can pivot freely. Remove the pivot pin to remove the float and needle. Usually, the rubber tip of the needle hardens and no longer can make a good seal against the seat or, the little spring that pushes up on the needle is gummed up and frozen. The float itself can fail. Shake it to see if there's any fuel inside it. You can also drop it into some gas and see if it floats. If everything looks okay with the float and the needle, you may want to pop the carb back on there and try running the engine. If that didn't solve the problem, now would be a good time to order a carb rebuild kit. These kits typically include a few new gaskets, a new main jet, and maybe a new pilot jet, a new gasket for the bowl, and maybe a new float and needle.

Remove the air filter housing. That means removing the cover, the filter element, the base, and this part. Notice this hose goes onto this nipple. You'll need to remember that when you reassemble it. So now we have access to the carb itself. Now that we've removed the two 10 millimeter nuts, the carb really isn't secure to the engine but we do have to disconnect this linkage which is sort of a throttle/governor connection. And, now is a good time to disconnect the fuel line.

You may be able to remove the carburetor without damaging the original gaskets but reusing gaskets can create new problems such as air leaks, so we recommend ordering a set of replacement gaskets before performing this repair. So, once again, we're going to drop the bowl and remove the float and the needle. Remove the main jet which is down in this tube. Sometimes, you have to modify a tool. I ground the edges of this screwdriver off to get the jet out of an old jet ski carburetor but this hole is pretty big so my screwdriver fits fine. It's a straight slot. And, remember that these are brass fittings in aluminum, so you don't need to use too much force. So, there's our main jet and that is the emulsion tube. Just look at how small the hole is in that main jet. The emulsion tube has many very small holes as well. Its job is to help mix the fuel and air so that it can be atomized before it enters the engine.

Now, remove the pilot or, idle jet, which is located here. To do that, you have to remove the throttle stop screw. This is plastic, so be careful when unscrewing it. Remove this spacer. This piece is the idle jet.

The easiest and most common way to clean a carb is to spray the heck out of it with carb cleaner. This usually works pretty well, but carb cleaner is nasty stuff so be sure to wear gloves and eye protection and use it in a well-ventilated place. A nylon-bristle brush like this is also great for getting some of this off if your carb's really dirty. Here's an inexpensive set of carb cleaning tools that you can get. Some of these little pieces really help get into the nooks and crannies. We've got lots of little ports here. You want to be sure to hit those with some carb cleaner using this nozzle. And then, depending on the size of the holes, sometimes these little brushes can get right in there. And now, we've got to clean the most important bit which is the jet. So, in this case, we've got one of the little cleaning tools. You can find the right size to clean that. And, we've got the pilot jet and sometimes these jets are so small that I've even had good luck with guitar string for getting in there. And the emulsifier tube also has some very small holes and the guitar string works great for those. And then, of course, blow it all out with carb cleaner. Compressed air is also really handy for blasting some of that junk out at the jets and out of the carb.

So here we've got a really filthy, well-used engine off of a plate compactor. So, let's get this carb removed and disassembled so we can clean it. Now, a great way to clean a carb that's this dirty is with an ultrasonic cleaner. It's one of the best ways to clean the crap out of the passageways that could be deep down inside the carburetor. This is a fairly large bench-top ultrasonic cleaner but you can get smaller, less expensive ones. They sell them to clean things like glasses and gun parts. Now, they may not be able to fit a carburetor all the way in and submerge it, but you can just run it multiple times and rotate the part until it's all been cleaned. Now, there are a lot of different thoughts about what to use for a solution that you put in the distilled water. Anything from Simple Green to Pine Sol or a specialty solution. Today, we're going to be using an actual ultrasonic cleaner carburetor and small parts cleaning solution. So, let's get this cracked open and get going.

With some of these tiny parts, one of these little mesh things from the grocery store can help you keep them from ending up on the bottom of the tank. One thing to keep in mind is that these parts should never be allowed to sit on the bottom of an ultrasonic cleaner; they should always be suspended in a basket of some kind. There's our carb. And, because our tank is so large on this particular cleaner but the parts are small, we're using just a Pyrex measuring bowl inside so we don't have to waste a lot of the solution. Only the distilled water in the Pyrex bowl actually has the carb cleaning solution, and that way we can use it and throw it out more regularly and keep it clean. So, our water is already hot because it's been on for a while and now we're going to turn the cleaning action on. So, we've run our ultrasonic cleaner for a couple of cycles. Notice that the water in there is hot and now we're going to pull our parts out and see how clean that filthy carb is. Now, you can already tell at least the superficial dirt that was on there, a lot of that has come off. And most of that will come off easily with a brush. What we really care about is the nooks and crannies deep inside. That's where the Ultrasonic Cleaner really does the best job.

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We have some little parts here. So, if these had been clogged, there's a good chance that the cleaner would have been able to break the deposits free. That gasket's cleaner. Still a little bit of superficial dirt. Ultrasonic cleaners aren't really good at getting thick dirt off of stuff; they're really more about the internal areas. That was our pilot jet and the bowl, still a little bit of sludge, but notice it's kind of moved. It's been freed up. All that's left is to get this button back up and slap it back on the engine.

Now that your carb is hopefully clean, reassemble it and install it on the engine. So, the emulsifier tube, the main jet, the float and needle, the float pivot pin. Don't forget the bowl gasket. On some carbs, you want to make sure that the bowl is aligned the same way so that it doesn't interfere with the movement of the float. Don't forget this little gasket on the bowl bolt. Reinstall the pilot jet next. Make sure it's fully seated. Then the spacer. And then the throttle stop screw. And, because this is plastic, make sure you don't get it cross threaded. It's best to get it started by hand and then you can tighten it. And, because we had to remove this, you will need to readjust the idle once you get the engine running again, but we can probably get it pretty close to where it was. Don't forget to reinstall any gaskets that you may have removed or replaced. For example, this gasket has a little hole right here and that needs to line up with this little slot here. Remember to connect this spring on the throttle cable first because you need to rotate the carb. And then, connect that throttle linkage first and then you can slide the carb on. This is a good time to reconnect the fuel line. Okay. Do not forget the choke lever. Put on the last gasket and then remount the air filter base. Make sure this rubber gasket is still in place before putting this base plate back on the air filter housing. Secure the air filter element and the cover. And now, if we've done everything right, we're ready to put gas in it and fire it up.

Does the engine run correctly now? If cleaning the carburetor didn't do the trick, the next step is to replace the entire carburetor. Sometimes, there's just stuff going on deep inside, either corrosion or clogs, that you'll never get out and you just have to throw that carburetor out. Replacement carbs are readily available for most engines and in the case of the Honda GX series, they are inexpensive aftermarket carburetors readily available, very cheap, and they generally work just as well as an OEM carb. Those are also going to work on a lot of the engines like the Raven and the Harbor Freight Predator that are basically based on the GX engines. There really isn't much you can do to adjust or tune one of these carburetors. Most of the carburetors on these four-stroke engines nowadays lack a mixture screw that would help you adjust the fuel-to-air mixture like you might still see on a two-stroke carburetor for something like your chainsaw. But, the only thing you can do is swap out the main jet. There are a few different sizes but even then the standard jet that comes in your car is probably going to cover most people in most of the lower 48 for most of the year. Now, if you happen to live in the desert or up on the top of a mountain, you might need something like a high-altitude jet kit, which is available for some of these engines. The air is thinner and that's going to actually reduce the amount of fuel getting in to match the reduced air oxygen that's in the air. Just keep in mind if you do install one of those kits, the engine is not going to be able to generate as much power as it might with the normal jet at sea level. Hopefully, your engine is back up and running after doing a deep clean on your carburetor or replacing it if that was necessary. If your engine is still not running right, it's time to go back to troubleshooting and try to identify the next most likely culprit.

Stay tuned to the RuggedMade channel where we'll be posting more tech videos like this one. Thank you for watching and let us know in the comments what other topics you'd like us to cover next time.