Amal Carburetors are found on many vintage British motorcycles such as Triumph, BSA, Norton, Velocette and others. In this video, Todd at Lowbrow Customs goes through an Amal concentric carburetor step-by-step, disassembling and explaining each part and also showing you how to install your throttle cable properly. These carburetors are quite easy to work on once you are familiar with them. If you have good, unworn or a new Amal carburetors on your motorcycle you will find them to be very reliable and easy to tune. Frustration or tuning issues come from worn out carbs with air leaks at the mounting flange due to warping, or around a worn out bore or slide. Other issues can be a clogged idle circuit. All of this is explained in detail in this Amal 101 video!
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You can read a full transcription of this video below:
Hey guys, Todd from Lowbrow Customs here. Today we're going to show you a little tech tip on AMAL 900 series concentric carburetors. We have these available on our web store. If you like this video, you can check out all of our cool videos on You Tube here.
All right, let's go ahead and get started. These are very basic simple carburetor. I do see some issues with 40 year old carburetors that are worn out. I get calls from customers on a pretty regular basis, where they bought a rebuild kit and they rebuilt their 40 year old carburetor, and it still doesn't work right. Well, I got to say, you just can't rebuild a worn out carburetor. You need not thank me now, you could thank me later after you purchase one of these fine, new 900 carburetors that we have on our website. Okay, let's talk about some of the components on the carburetor. Let's start with this button here on the side, this is called a tickler.
Basically, what this does is, when you depress this, it has a pin inside here that pushes the float down. Which in turn, lets the needle come off of the seat and will essentially send some fuel into the bore for starting purposes. You may notice on your original carburetor that the button is very small and when you depress it, it gets gas all over your finger. This is one of the nice features on the new carburetors. It has this extra piece on here, so when you push it down and when you're using your tickler, you're going to push it down and hold it. You're not going to pump it. It's not an accelerator pump. You're not pumping it to get some fuel in there.
You're just going to depress it, hold it down, and fuel emits, it's ready to start. One other thing worth mentioning is if you have a dual carb application such as a T120 Triumph Bonneville, you will be doing a left and a right carburetor. The only difference between a left and right is where this tickler is located. This carburetor I have for the demonstration purposes is in fact a left carburetor because when it would be mounted on the motorcycle, on the manifold, the tickler will be facing the left. Also the adjustment screws will be on the left or the right. If you're doing a single car bike like a Triumph TR6, you would order a right carburetor because that is what they came with from the factory.
Okay, that's our tickler. Let's go ahead and remove the lid, and take a look at what's inside there. Simply remove these two Phillips head screws. You want to just support the lid because there is a spring inside here that you'll see in a second. [removing the screws] Two screws, take lid off, there's your spring. This is the throttle slide, keeps the slide down in the bore. Also gives you that nice action on your throttle control. Go ahead and take our slide out down, we'll leave our choke components in there, except they just fell out. This is the choke right here, this hole and below it, the spring and slide.
Here’s your needle, next component in here. It has some grooves on there and a removable clip. That will allow you to lean the mixture or enriching the mixture. Setting your clip on a higher setting will make the mixture lean. Lowering the clip will make the mixture rich. Okay, one of the thing worth mentioning at this point time is, this what the lid will look like on the carburetors when they come to you in the box. It has these two threaded adjusters, one is for the choke-- This one is for the choke, this one is for the throttle cable. As you can see on the underside of it, the spring for the throttle indicates in that spot and a little tab from the choke indicates on that spot.
On bikes equipped with choke cables, this will raise or lower that for starting purposes. On the majority of the custom bikes I build, I basically remove these three components from the carburetor and do not replace them. If you would like to plug this hole which is a good idea because you don't want to be pulling extra air into the carburetor, we have this part here which is simply a plug made by AMAL that has the correct threads to plug that hole. Okay, that’s all that's in there. Let's go ahead and talk about the lower portion of the carburetor. This is going to be your fuel inlet.
A couple of things worth mentioning about that is, if you were putting this on a single carb application, you would want to have a dual banjo. In other words, there would be a fitting on each side for the fuel to come in to the bottom of the carburetor for the float bowl. We do have those available on the website. This is how they come to us from our supplier from AMAL Carburetor company. The reason you do want to have a dual on there is, if you have a stock gas tank, you're going to have a fuel valve on each side of the back end of the tank. That way, you'll have two lines going to the carburetor. If you have a dual carb application, the stock ones like Triumph for instance did have the dual banjo.
What they did then was they had one line coming from the gas tank to each carburetor and then they connected the two carburetors together at the bottom. Basically, what that did was equalize the gas in each float bowl as they were coming in, filling it, equalize it. I have personally used carbs with the single fitting on a custom bike by utilizing one valve on the gas tank per carburetor, and not had any issues with not having the crossover. Okay, if we go ahead and take this fitting, right here, off, what we're going to find under here is going to be a fuel filter. This is hollow, has a hole on it, that lets the gas come in through here, go through this into the float bowl.
There's our fuel filter. A little mash filter keeps impurities from the gas tank going into the needle and seat, which would probably cause your carburetor to flood if it didn't have this filter on there because if any particle, dirt, gets in that needle and seat area, we can't close. There is a fitting on the bottom of the carburetor that can be used to drain the float bowl. This right here. Both of these fittings will have a fiber gasket on them. Those have to be in good shapes so it does not leak fuel. If you want to change a jet, the main jet, you can see it's right there underneath the plug I just removed, simply you can use a 5/16 socket. You can change a main jet without taking the bowl off of the carburetor.
There's your main jet. Okay, will go ahead and remove the bowl now, see what we have going on inside there. Once again, Philips screwdriver. It's a good idea to turn the carb right side up when removing the float bowl, so the components don't fall out. You're going to find your float bowl gasket and your float and needle. This is one of the new floats that they've been using for some time now. This is what AMAL is calling their Stay-Up float. It is ethanol resistant. This is your needle that controls the gasoline coming in. There's a seat right there, as the needle comes off of the seat, that lets fuel come into the bowl. Float controls that by going as the fuel is being used by the engine.
It's consistently staying open or closing depending if it's full of gas. If you come to a stoplight, obviously, it's going to shut down. It's going to run what's the fuel that's in the bowl. As you start going again, it's going to see a need for more fuel, and it's going to lift back up off the seat and let more fuel into the bowl. It is important that your float level is correct. This is the previous float that was being used by AMAL, a white plastic. This is what you might find in an older carburetor. Not adjustable. This one has a metal tang that you can slightly bend to adjust the float level. You can find any of these specs will come with the new carburetor.
There's a very nice tuning guide that comes with the carburetor with some really good information in here. If you're new to this kind of stuff and you order a carb from us, and you're not quite understanding some things, you can always give me a call. I'm available Monday through Friday to take your calls and answer any questions you may have. Okay, what else do we want to talk about here? Let's take this other fitting off of here which is your jet holder. What we're going to find on the other side of this is your needle jet. That's right here. Which can also be removed by the 5/16.
These carbs will come with a 106 needle jet that's pretty much standard across the board for British motorcycles. If you could see down in here, you would see there's a taper, and that's what denotes the size of that. Your needle rides inside of this and controls the flow of fuel. At idle, you're on the idle circuit on the carburetor, and you're not even using this. As the needle raises up, it meters the amount of fuel that's being fed to the engine. Thus, as we discussed earlier about changing the clip setting, will raise or lower this in this jet. Now, the other thing we have going on here are these two adjustment screws on this body, on the side that will be facing out on a dual carb.
Single carb, you'll have a right carb. You'll be adjusting it from this side. Flat-head screwdriver. The one that is facing at an angle right here is going to be your throttle stop screw that basically sets your idle. If you notice on the slide, there's a flat spot where-- and there's also a slot on here that coincides with this on here. When the slide is in the carburetor, and you are threading that screw, it is essentially moving that slide up or down to adjust your idle. The other screw that is facing straight in, that's going to be your air fuel mixture screw. We'll go ahead and remove these so you can see what the difference between the two because you don't want to mix them up.
Removing the throttle stop screw. It has a flat end that coincides with this. You also notice that there is an o-ring on there. There's also going to be an o-ring on the air fuel screw, and the o-rings aren't so much there for sealing purposes. They're more there for to keep tension on the screw once the settings been-- once you've achieved your correct idle, correct air fuel. If it didn't have the o-ring on there, the vibration of the engine running and going down the road could cause it to turn and alter the settings that you put on there, and you want that to remain the same. So anytime you're working on these carbs, you want to be sure that, that o-ring is in good condition.
That's all there is to it, on this carburetor. That's all your components right there. There's not a whole lot going on here. These are very reliable carburetor. They work well when new. There are some things that go wrong with them when they start to get older, and they've been worked on by several different people. We'll go over those things right now. One of the biggest things I see on these carburetors from working on these old bikes pretty regularly is I will see the flange right here will be warped. Bodies are made of aluminum, and if you're tightening this thing down on the manifold, there's two nuts and studs coming off of the cylinder head.
If you over tighten those two nuts, you can very easily warp this flange. Sometimes it's very apparent or if you sight down the carburetor, you can plainly see that it's got going like this. If that happens, you also have an o-ring right here on the flange that helps seal the carburetor to the manifold. If you find one that has a warped flange, essentially what you're doing is it won't seal to the manifold, and it could pull more air into the carburetor which will essentially lean the mixture out. That's last thing you want is a lean mixture. It will be also very difficult to tune because it's pulling more air. Basically, if you see one with a warped flange, I have seen where some guys will put it on a flat plate and sand it down.
It's generally not worth your time. If that's bad, there's probably other issues with the carburetor. The other thing I see very frequently is the slide will stick in the bore. Notice how that slide in this carburetor just goes in and out of there, no problem whatsoever. Sometimes when you're taking one of these apart when it's an original carburetor, it will get to about this point here, almost out, and it will be stuck, where you have to physically pull on it. I've had times where I've had to take a pair of needle nose pliers and grip this portion of the slide and yank it out of there. Not a good thing. Part of the reason that happens is, as things where it gets stuck in there.
The other main reason that happens is, once again, over tightening the mounting nuts can distort the body of the carburetor. Now, you have a round hole that is no longer round. It is out of round. The other thing I see on these carburetors if you have a leaky float bowl, once again, over tightening the two screws that hold the float bowl on. You can see the bowl will also get warped, where no get new gasket in the world is going to stop that float bowl from leaking. One of the last things I'm going to tell you about, that is a big issue on these carburetors is, if you could look down inside that hole you're going to see the pilot jet. The pilot jet controls idle, the idle circuit.
There's some very small holes right inside here, and when there's no throttle opening at the handlebar control, it has to pull-- it meters the fuel to make it idle. If you find that you have just resurrected one of these old bikes and you've cleaned the carb, and you're getting it running, it hasn't run for a long time. You depress your tickler, it starts, it runs, and then it dies. Now you depress your tickler again. Yes, it starts, it runs, then it dies again. More than likely your pilot jet is plugged up. There is a tool that you can purchase to go down in there and clean it out. Ethanol fuel is really bad. It will plug up one of these carburetors very quickly.
Leaves a residue on everything. It's a very good idea at the end of the season, take this plug out of the bottom of your carburetor and drain your float bowls for the winter time. Some people like fuel stabilizer. It's actually, I just make sure there's no fuel. Some guys say, they want to fill the tank to the top which is not a bad idea, so you don't get moisture in there. The best plan of action, if you think you have any ethanol and your vintage bike drain the gas completely, get rid of it. Put fresh gas in, in the springtime. Okay, moving right along, the next thing we're going to do is we're going to install a-- Show you how to put a throttle cable on one of these and attach it to your throttle control.
Okay, now we're going to show you how to put your cable onto the carburetor and attach it to your throttle control. As discussed previously, we have this threaded adjuster in the lid of the carburetor. I think you're going to find that the majority of the cables out there available today are going to have a top hat arrangement on them, like this one has. If you find that your cable has this style end on it, it will fit into the threaded adjuster with no problem. If you find that your cable has this top hat arrangement, you will find that it is not going to fit into the threaded adjuster.
What we're going to need to do is to remove the threaded adjuster and simply drill the threads out of the the lid in order to let that top hat sit flush with the top of the carburetor. If you were to install this top hat style cable with this adjuster in this lid, you would find that your slide would be hanging way open. The bike would never start and run and if it did, it would be idling so high. It would sound like it was going to blow up. I'm going to show you a really easy way to do this. What I generally do in my garage when I'm putting installing a new carburetor that has that style is I simply get a block of wood and a couple of drywall screws. The reason I'm doing this is because if you ere to try to hold that lid in your hand while drilling, I guarantee you it's going to spin around. Basically, this just simplifies a simple process even more. Just takes a second.
If you have a vernier caliper, that's a great way to measure the end of your cable to determine what size drill that you want to use on there. Okay, we've got it set to-- We want to do a fraction. We were on decimal, we want fraction. There we go, fraction. Basically, just put this in the nibs of your tool. I'm seeing 15, 60 force. What we'll do next is we'll grab our drill index and we'll take the 15, 60 force out there which I've conveniently already installed in my drill motor here. Then we'll go ahead and drill this lid. Bada bing, bada bang. Make sure you don't have any of this swirl from drilling the lid on your workbench if you're reassembling your carburetor because you really don't want that stuff in there.
Now, we're just going to go ahead and remove it from the wood, verify that our cable fits. Viola, look at that, fits perfectly. Okay, now, when installing in an existing cable or a new cable, you're going to want to put the cable through the lid, and you're going to want to put the spring on next, return spring, and make sure that's located in that spot right there. Then what your going to want to do is you're going to compress the spring a little bit because you'll see here, there's a hole in the slide. What we're going to do is there's a hole in the center that the cable will go through, and then you'll move it to the other side where it'll stay in the hole. That's what that looks like.
But we also must install our needle at this stage of the game. Once again, you're going to hold the spring away from there, and the needle is going to go down through the center hole that we used to put the cable in. You'll see that it needs to face that direction. Obviously, can't go the other way around. Then you're simply going to install this in the carburetor, making sure that the knob is going to coincide with the body of the carburetor. You can look down in there and be sure that the needle is going down into the needle jet because if it's not, if it's hitting the side of the carburetor-- Then finally, when you’re going to put the lid on, you want the cable hole to be facing towards the intake side.
In other words, you want where we put the plug for the choke. If you were to take that back off and look in there, you would see that the choke is on the side of the carburetor, so you don't want to put your lid on backwards because the cable won't actuate correctly if the lid is on backwards, and you can't put it on backwards. We'll put our two lids screws in there, once again snug those up, they don't need to be cranked down. They do have tiny lock washers on the screws, these screws are captive on there, so you can't lose those. Now we’re ready to put the cable onto the throttle.
Here's what your typical throttle will look like for single cab application, you're going to have one hole; dual carb, you're going to have two. There's also this cable abutment that's necessary. We'll go ahead and take this apart. You'll see that there's a hole for the barrel that's on the end of your cable. We're going to turn our adjuster all the way down to give us the most slack on the cable. Then you're going to put the cable through the hole, doesn't matter that it's going to come all the way through like that at this point in time. You're going to put that in there, making sure that it can move to go into the cable groove on the throttle.
If you have a hard time getting this in there, it's really tight, doesn't want to go in, it's not a bad idea to take a drill a bit and just remit just slightly, so that this fits in there nice and loose. You don't want it to be super tight because then you're going to have a harsh action on your throttle. Okay, then you're going to go ahead and put the two halves together. You may notice right now that it's not going together because this has to be turned, see right there, now the two halves can go together. You can't have that portion of the throttle tube up against this or they won't go together. It has to be on that side of it. See how it is there? Okay.
Now we're going to go ahead and put our two screws back in the throttle. Also if you are using a new cable, don't forget to lube the heck out of it. You're using an old cable, it never hurts to lube the heck out of it. Okay, last thing you're going to want to do is you're going to pull this, seal the cables up inside the hole. That's obviously not going to work right, we still have our abutment to put on there. You're going to pull your cable, you can hear the slide moving in the carburetor. You're pulling it up, obviously, the small end is going to go into the throttle control. Like so. It’s much easier to put this on last. If you try to put your cable in there, you might not have enough to get it closed.
The other thing you can do when it's all the way together is you can check the operation of your throttle to be sure. Before you stall it on the handlebar, put your carb on the manifold. That's all there is to it. Hey, thanks for watching our video today, you can find all these great products on our website lowbrowcustoms.com. After you get your new carb on your bike, get her dialed in, go for a ride!