Cleaning the carbs 1: Difference between revisions

A #2 phillips, assorted flat blade screwdrivers and a length of copper wire. Not shown is the #4 allen used to put back the replacement screws. The copper wire is '''''essential''''' for reaming the passageways and helping clean. Any metal more aggressive than copper has a very good chance of hurting the carb internals and making them not operate correctly. If you just mess up jets, well that's a $5~7 per item mistake, but if you scratch a passageway, then you're looking at a new set of carbs. And it's essential in the same way a toothbrush is, vs. just rinsing with Listerine... you need to scrub the tough bits that are stuck.  

The floats do this by floating (duh?) on top of the gas, and pushing the fuel needle against its seat. The fuel needle (shown below) should be inspected to ensure that the rubber tip is a well defined cone. If there's a dish in the middle, that means it's worn out and needs to be replaced. Worn needles will leak fuel into the carbs, which will then leak into the engine and flood it, as well as leak past the rings and contaminate the oil. Just a whole ball of wax best to avoid:  

You'll want to remove all of the above items prior to cleaning, except the enrichener pickup; that's part of the carb body. This should leave you with just an empty looking float bowl (well, the top of that chamber, bottom of the carb itself). This is the 'meat' of the carb. Up top is just the slide and needle (which will be touched on later in this article). You need to probe each and every hole with some wire. Twist a few strands together for the big holes, and just use 1 piece, slightly kinked up, for the smaller holes. You want to be sure to get ALL of the holes, like these on the side of the pilot jet:  

The pilot circuit, also called the Slow Speed circuit, has the smallest holes/passages. They are the first to clog and are deserving of the majority of the attention. The pilot circuit outlet:  

Take the compressed cleaner and, using the straw, squirt fluid into each and every hole. You should have cleaner going into or coming out of each and every hole, though not all at the same time, and in the same volume as the other carb bodies. And it should be coming out Clear (this one started greenish).  

When it comes time to reassemble, the jets just screw back in, but you need to set the float height. Each set of carbs has a different recommended height (listed in the service manual for the given bike). If the floats hang too low, your bike can (and most likely will) run lean, and if they sit too high, you'll likely be fighting a rich running bike. The picture shows a special tool for measuring float height, but a 6" ruler, or even a basic set of calipers, can be used to measure the height. To measure, you want the floats to Just be touching the fuel needle (which has a spring on it, you don't want to compress that) ~ most carbs can just be set upside down and the spring will hold the floats where they need to be ~ some carbs you'll need to tilt at an angle while doing the measuring. To adjust up or down, you just bend the small metal tang that rests on the fuel needle:  

With that set, feel free to screw the float bowl back onto the carb. It's best to replace all the phillips screws with stainless allen screws, as they're easier to work with (cost about $12 at Ace hardware to buy replacements). Float bowl screw size is M4 0.7 pitch, with 14mm length. Commonly written as M4x14 0.7 , although you may want to bring your old ones with you, just to make sure. If you have to get slightly longer screws (say, 16mm), that will work fine.  

Up on top, you have a diaphragm that controls the speed at which the slide goes up and down via high and low pressures, and that raises the needle, which directly controls the midrange fuel delivery. These are traditionally set a bit low to lean out the bike for EPA emissions when importing the bike. The most standard fix is to just put a couple [[Washers for carb needles|2.5 or 3mm washers]] on the bottom, so the needle is raised up a little from the start.  

That's the only adjustment that can be made up top. Make sure that the diaphragm doesn't get damaged or pinched when you reassemble ~ the carbs won't work right and they are expensive to replace! Test all the slides by just pushing them up with a finger and comparing them to banks you haven't touched yet, or just make sure they all react the same.  

That's all there is for cleaning and adjustment Inside the carb. There is one other adjustment outside of the carb, and that's the [[Removing idle mixture screw plugs|air/fuel mixture screw]]. This is the item that has the plug covering it from the factory (anti-tamper plug is what it's usually called, or "EPA plug"). You need to drill a small hole in the plug, then screw a screw into it and pull the plug out ~ it's just a pressure fit. What you'll be left with is the screw that meters the air OR fuel for the pilot circuit (if the screw is on the engine side of the carb, it meters the fuel ~ if it's on the airbox side, it meters the air)... Again, this is set to the lean side from the factory. By adjusting this screw, you can help cold start issues... a good base setting is 2.5 turns out from fully seated:  

And that's it for what can be done on the bench. When you [[How do I remove the carbs to work on them?|install the carbs again]], you'll want to [[How do I synchronize the carburetors?|do a carb synch]].