How To: Carburetor Linkage Inspection

Added: 2026-05-31

[00:00:00]Hello, this is Brian Searter with BBS Race Engine Development. Today, we're going to start our deep dive into the K100 carburetor. Uh the early videos in this playlist are going to be a little more uh elementary level, but uh on the mechanisms and basically how the carburetor works and some things to look for. But as we go farther along, we're going to get deeper and deeper into the carburetor and proper ways on how to tune it, how to get the most of most out of the carburetor so you can have the best day at the track as possible. So, let's dive in.

[00:00:50]One of the first things we're going to get into on these carburetors is the inspection of the throttle shaft and linkage system here. We see common issues come through the shop where a lot of the stuff is very worn out. It causes the throttle to not work properly. The throttle blades not shutting properly.

[00:01:07]Sometimes they're over center where you're getting far more than wide open throttle. So, I picked this carburetor here up and initially, um, I'm going to point out a few things that I see before we take it apart. Uh, the issues that I typically see, one is you can notice there is some wear on the shaft here where the clip goes in. So, while that doesn't seem like it's necessarily a big problem, as you can see, as I open this throttle, everything shifts towards the right. And as it shifts towards the right, that will cause your throttle blade here to rub into the body of the carburetor itself. And as you can start to see, if the camera can can see it close enough, you can start to see where there's flat spots getting on the edge of the throttle blade there that um where all this is wearing and because the throttle shaft is being pulled to the one side. One thing that exacerbates that that we see a lot is the fact that this cable holder is not in line to where when the throttle cable is pulled that it pulls directly in plane with the rotation of the shaft. So, as you can see, this one here is pointed at a different angle. So, as the cable pulls to open your throttle, it's actually pulling the shaft over to the right. And that is a lot of what causes this wear on this part of the shaft here and causes your clip to get worn and also wears on the throttle shutter and the body itself causing air leaks through, you know, when you're off idle and things like that. So, we're going to get this torn apart and then we're going to show you what these pieces look like and what to look for. Um, it does look like everything is somewhat okay with this carburetor. the the throttle spring is still in good shape. So, you know, we're going to take this apart. We're going to look at each of the components of it and then we're going to rebuild it so that way it is as good or better than new.

[00:03:14]You can see where it's digging in there already.

[00:03:25]Okay, we've got this carburetor throttle linkage apart here. And so we're going to go through some of the components and some of the uh wear that I see on some of the items. The first thing that I see is on the throttle shaft clip that actually holds the throttle shaft into the carburetor. It is very worn on this edge. And I'm not sure if the camera can quite zoom in on it, but you can see it's over halfway worn through. So once that gets all the way worn through, the shutter is the only thing holding your throttle shaft in the carburetor. So that definitely needs replaced. The other thing that I noticed on the throttle shaft here, you see where there's like notches where that shaft clip has been rubbing and it'll wear over time and you're going to get some wear. This one isn't horrible, but by the amount of wear on the clip and the wear that I see already on the shaft, we're going to go ahead and replace that as well. Another thing that I've noticed as this carburetor has ran over the years and these parts, other parts being worn, you start to see this step here on the uh throttle, they call it a shutter, throttle blade, throttle shutter, whatever you'd like to call it. But you can see where that's starting to create notches. And that is from this here in the carburetor where you can see where the shutter has actually been wearing into that. You can see the wear marks. So over time that's going to dig a gouge in there and cause air to leak past that. So we're going to replace the throttle shutter as well. Um the spring looks good, but springs are cheap. So we're going to go ahead and replace that as well. um inspection of the throttle lever here. Everything looks pretty good. Got a little bit of wear where the u where the throttle stop is, but uh that that looks pretty good.

[00:05:12]So, we've went ahead and pulled our um throttle stops out as well. So, we'll reoctite those and adjust those to where they need to be. So, uh we'll get started on the reassembly. The first thing I'll do is I take the throttle shaft and kind of an easy way to look at it is like have your carburetor there so you know how to put this on because you can put it on wrong and but it'll only go together really one way but you'll just find out later is the problem. So you go ahead and put that on. Get your screw. It's already got Loctite on the screw from Miami. So then you need to make sure you get these screws tight.

[00:05:46]What I do in order to make sure it is snug and tight is I will actually grab it with a pair of pliers like this so I can hold it and then I would take the big screwdriver and really get a nice nice torque on that because that does tend to come loose over time. So now I will check that to make sure that I don't have any motion in that shaft between that and the lever. So then we install our spring. Slide that through the carburetor just like so. Then you take your clip. I always put the clip so the side that has a little bit of a radius where it has been stamped that it is facing the direction that the shaft is going to get pulled. So it's less likely to dig in and wear. So we'll take that. I know a lot of people use a lot of Loctite on these screws to try to hold this in, but I feel that if you get it properly torqued and you properly tighten the screw, you don't need it. Put the screw in. Make sure it's good and snug. You know, doesn't have to be overly tight, but it needs to be good and snug. And then feel that to make sure that everything works smoothly. because sometimes if this gets pushed one direction or another as you're snugging everything down, it'll cause some drag on the shaft. So, that there is working very smooth. So, the next thing we'll do is we'll take our new throttle shutter and we'll put it in and let it close all the way. And I'm letting it close all the way without the stops in there. So, that way the shaft finds its proper home inside the bore of the carburetor. So, we take our screw.

[00:07:31]Already has some Loctite on it.

[00:07:36]Snug it down good and tight. Check to make sure it's shutting properly. Make sure you don't see any um any gaps around there. So, I don't really see any light through there. So, that means the shutter is stopping properly on the body. So, the next thing I'll do is we're going to set our throttle stops.

[00:07:54]Something that happens quite often is these tabs get bent and then people tend to over, you know, compress your uh your adjusters and the springs get collapsed. So, you can either get a new spring or you can do a little trick that I've got where I just kind of grab the spring with a couple pair of needlense pliers.

[00:08:12]You just stretch it out a little bit on that side. Try to stretch it even. So, now it's stretched out to basically its normal length. And now you can use this.

[00:08:21]So, the first thing we'll do is we'll set the top stop. And this is the way I do it. Some other people may have different opinions on how the throttle needs to be stopped, but you know, we're going to do it my method. So, you put a little bit of Loctite on your screw.

[00:08:37]Doesn't have to be a ton, but you got to have, you know, enough to to hold the thing properly. You don't want it walking out because most of the time on the track, the throttle is open. So, and then what I do is I'll bring this adjuster screw down just until it touches the B or the uh throttle lever here and we're still shutting. And then I'll turn it a good one half turn. And then that gets it to where when the throttle is actually shutting and coming stopped that is actually stopping here on the screw adjusting screw and not stopping because the shutter has uh come in contact with the body. So this will save you wear inside the throttle bore. It'll save you wear on the uh the throttle shutter. So we've got that one in there. And now we'll put in the throttle stop for the opening side. the same thing. Just a decent amount of Loctite.

[00:09:34]Get that started in there.

[00:09:37]And sometimes this takes a little bit of work because you want to get it to where the stop is in the center of the throttle lever assembly. And sometimes these don't match up. So you got to do a little bit of bending and tweaking of these to get everything lined up the way you want. This looks like it's stopping very good. So, as we're stopping here, you can see where that is coming in contact right in the center of this throttle lever. So, that way when it is stopping and you're hard on the throttle and pushing with your foot that it's not trying to push this thing one way or another. So, um, so we got that set.

[00:10:13]Now, we do either the calibrated eyeball where we get the throttle center set to 90°.

[00:10:23]There are some tools you can use for this, but I've been doing this for many years, so I can uh get it to set basically right at perpendicular. You want that blade right perpendicular. Uh sometimes we will put them a little purposely under center because when um people are in the go-kart and they have their if they get their cable set up to where it's too tight and there's not enough slack, you will always push harder with your foot than you will with your hand when you're setting up the throttle on your go-kart. So, we see a lot of these come back where the throttle is way over center because it has pulled so hard that it has bent this lever down. So, that's just another little tip. And then the last final thing we're going to do is we're going to use a little adjustable wrench here and we are going to adjust this cable holder to where it is right in line. So when it the when the throttle cable pulls it pulls directly perpendicular to the shaft. It pulls it straight down. So that way there's no binding and no pushing. And just take an eyeball. You can lay a screwdriver up there. It's just it's getting close. So we we'll tweak it just a little bit more. Yeah.

[00:11:31]So that's pretty good there.

[00:11:33]So, we now have this carburetor as good or better than new. It's going to be more reliable. You're going to have less chance of failures at the track, and you're going to stop some of the wear that would continue on this carburetor if these components would have left been left to wear. That's it for this video.

[00:11:51]We will dig deeper into the next one.

[00:11:54]Thanks for watching.