Now we get to the boring bit – cleaning! But in respect to a carburettor, it’s the most important part because if you rush it and cut corners you will be pulling the carb out of the bike again – I guarantee it! The hardest parts to clean in a carb are usually the ones that block and cause trouble in the first place. Take your time and get everything as clean as you can and you will have success. Let’s get into it…
OK…what will we need in the way of tools and consumables? I have already covered the screwdrivers required and what to watch for in relation to them. You will need a can or two of carby cleaner, compressed air, a small brass brush, cotton buds, rags (preferably clean and white so you can see what comes off on them), your workplace needs access to strong light so you can see through the holes in the metering jets to make sure they are clean.
As for safety – I have already mentioned gloves, some eye protection is essential because you will be dealing with high pressure air and cleaners. I prefer the full face shields because I am ugly enough thank you very much and I don’t want to be made more so by high-velocity bike bits! Think about ventilation and air circulation as well – too much carb cleaner vapours are not good for health.
What about an ultrasonic cleaner? Do you really need one? If you go and spend some bucks on a cleaner don’t think it’s going to do all the hard work for you. Cheap ones will do a reasonable job but only expensive, dedicated high power units will get them close to spotless. The cheaper ones like the one I use will get stuff reasonably clean but can’t go the extra mile with hard to move deposits. Do you really need one? No, not if you are doing just one carb. Just get yourself a couple of cans of carby cleaner and don’t be scared to use it.
Even if you do have a ultrasonic cleaner, if your AG is fumy and the carb was sucking a lot of oil vapour via the crankcase breather, a cheap ultrasonic cleaner may not get the job done. A solvent like carby cleaner will be needed to clean the baked oil residue out of the venturi of the carb. This is a good “tell” on the condition of your bikes engine; black oil residue in the main air-flow passage? You are probably going to have to do some engine work soon. But let’s get the carb sorted first.
I separate the components into two groups; the main body parts, and the small, functional parts. I can place the carb body, float bowl, throttle shaft, cable bracket and other larger parts into the bath of my cleaner. You may have a different size and have to spread your cleaning out differently. I pour hot water into the bath and add a small amount of dishwashing liquid and set my heat on max (70C in my case) and run the ultrasonics for an hour. Sometimes I have to give it another thirty minutes or so but an hour usually gives me pretty good results.
The brass brush will come in handy here. Use it to break up any caked on crud on the outside of the carb body. Pull the parts out of the cleaner one by one every 10 minutes or so and give them a bit of a brush if stuff is hanging on. Don’t try and jam the brush down the venturi if there is baked on oil, let the carb cleaner do that job later.
When the parts are done, you need to get them dry. If you live in Australia or another country with an excess of sunshine, get them into the sun and let them cook! It won’t take long for the Aluminium and Brass components to heat up to the point where water won’t hang around them. If there is no sun to use, get them in front of a heater to dry off. Temperature and time is what you need to get them moisture free. Of course you can use compressed air to blow all the water out, which I do but I also like to heat it up as well. If you’re happy with just the air then happy days.
Now that everything is relatively clean and dry, it’s time to get serious with the carby cleaner. Let’s start with the carb body. You have your gloves and eye protection on right? Give the carb a good blast with the cleaner and try and let the cleaner sit on the aluminium without evaporating. Lower temperatures will help here so try and do it out of daylight. Letting the cleaner soak into any deposits will help you a lot. If there is significant oil deposits in the venturi, use a rag covered finger soaked in cleaner to give the area a good scrub. Some cotton buds soaked in cleaner may help in harder to get areas. Blast the whole thing with compressed air paying particular attention to the small passages leading to the pilot jet/bypass and choke plunger. Rinse and repeat!
In this photo at left you will see a view of the bottom of the carb looking into the upper float chamber – see the arrow at the bottom pointing into a large hole? That’s the float chamber vent. In some bizarre law of physics that follow the same laws as coat-hanger reproduction and socks always being odd, grass seeds accumulate in this part of the AG200 carb. Don’t ask me how they get there but they do!
Now onto the smaller components. With or without an ultrasonic cleaner, you now need to focus on the brass jets. They are the heart of the fuel metering function of the carby so they have to be spotless for it to function correctly. Clean all the brass jets until no more crud comes off them onto your clean rags. Soak them like I recommended for the body above.
Take a close look at your emulsion tube and look for the sixteen small holes (1) in the body of it and make sure they are all clean. Use the four holes on one side to line up with the four on the opposite side – light needs to shine through all eight. Have a real good look at the top of the tube (2) where the needle goes in and if you see any wear or elongation of the brass, replace the emulsion tube and needle as a set. Have a good look at the needle’s taper particularly at the upper end (3) and again, if wear is present replace the set as stated.
I probably should of left this to the next part of “inspection and assembly”, but like the rubber diaphragm mentioned in my last post, if you don’t want to pay the money for parts then this is the time you stop working on your carb and start looking for another one to clean up. The bike will run like a dog with these parts worn, and no amount of carb tinkering will get it to run right until you replace them.
The fuel needle valve is next…was it leaking fuel before you stripped the carb? If it was, don’t chuck it out just yet. The rubber on the tip of the needle is very robust and I would suspect the valve body myself. This is a problem area on the AG200 because there is a filter gauze on top of the valve that you would of seen when you pulled it out of the main body. Without a proper fuel filter, anything that gets past the tank filter will accumulate here and can make a bit of a mess. Gently pry the filter off the top of the valve and soak the whole thing in cleaner or put it back in the ultrasonic bath if real bad. Remove the O-ring if it hasn’t already disintegrated. I have found that sticking a cotton bud soaked in carb cleaner and rotate it in the needle side of the valve will nearly always get it working again. Physical wear is not really an issue with these valves because it’s rubber Vs brass, and the rubber is pretty tough. Corrosion is nearly always the culprit and once hit with some chemicals they nearly always work well again.
Soak the pilot, pilot air, and main jets in cleaner and blow them out. Make sure you can see through their metering holes and that there are no obstructions. Don’t go sticking things in the jet’s metering holes if they are blocked, be patient and soak them in cleaner and use compressed air – it will shift the deposits eventually. Don’t forget other brass bits like the throttle butterfly, choke plunger, pilot air screw adjuster and get them as clean as your persistence and patience will allow!
For all the other parts, I suggest a brush over with the brass brush to clean them up. Bits like screws and their threads clean up well with a bit of a brush up. Try and keep carby cleaner off rubber parts like O-rings and the slide diaphragm. They don’t like it but it evaporates pretty fast so don’t get too concerned. Most of the small O-rings like on the choke plunger bolt, needle valve and on the pilot air screw adjuster will probably be stuffed, but I will discuss all this in part 3.
For now we are pretty much done with the clean. I didn’t get too detailed – it’s all common sense really. Just get things as clean as you can and blow it all out and you will be done. Next we will cover re-assembly and what to look out for and some other tips.