Honda Grom Exhaust Installation | Honda Grom Koso Throttle Body Installation | Partzilla.com

Hello John Talley, here with Partzilla.com, and welcome back to our next installment on our 2018 Honda Grom build. Actually, today we're going to focus on the intake system and

exhaust

. We're going to change the

throttle

body

, we're going to put in a high-flow injector, we're going to have a high-flow air filter and then all of that is going to be channeled through a new

exhaust

system. Now this is the second part of three if you want to loosely call it the engine build. Now, when we get to the third part, that is when we will deal with air fuel management.

The good thing about this one? When we finish building it, we will give it away. So if you check the link in the description below it will take you to a landing page where you can enter to win. But if the contest is already over, why don't you leave this little note in the comments section and tell us which machine you'd like me to modify and then we'll give it away? With that being said, let's go ahead and get started on this one. So the goal here on the teardown bench is to make this look like it came out.

So we'll start by transferring the idle air control valve and

throttle

position switch. Very good, they are held in place with Torx and the screws and it is a T25. So we'll start with our throttle position sensor. Let's see if we can gently pry this off. Here we go. Then just transfer it. It just goes back to its place. Now there is no setting in this case. I have seen on other units like the TRX 420 that it is actually grooved and has to be marked by taking a resistance measurement. Obviously, in Grom this is not the case: a placement period.

Now that we're on this side, let's go ahead and take the air fuel screw or the idle fuel mixture screw. Now we're just going to transfer that in. We'll touch it lightly all the way down and then back it up two turns. Alright, that's bottomed out. One two. Next let's go for the idle air control valve and that was also the T25. Who would have thought all those years ago that a simple little minibike would now have all these complicated things? Guess I'm really showing my age, huh? Well, the basic design of a minibike, when you think of a QA 50, it just had a simple carburetor and now here we have throttle position sensors, fuel injection and everything else of a modern machine.

Now we are going to mount the throttle

body

to the actual intake. Get our O-ring. I'll just sit like this. And we are simply reusing the two eight millimeter head bolts that came from the OEM, that is, the original. Yes, I think we need to bring that support here. Compare these two. Tell me that's not going to take any more air. Big, big difference. Now all these pieces, when they come together, it's going to be nice. We'll go ahead and put this little spacer in place. Now you have these three threaded areas here, and if you have the stock injector going back in, just use those two.

But ours will only use the only one in the middle. Now let's get our adapter kit and put our high flow injector in there. Now a note, with this particular setup in 2018, the inlet was going to interfere with the plug that goes to the idle air control valve. So I warmed it up a little and folded it just enough to lighten it. It wasn't in the instruction book, but that's how I solved it. Now let's work on our injector. Now this one actually has an O-ring around the bottom, so you're not going to use this other rubber O-ring if you want to call it that because it's actually made for the stock setup, or the stock injector.

Now, we need to set up our adapter on top of our injector. That goes in there and then this little clip slides in to hold it in place. Now we will take this assembly and push it into the inlet and you should hear a click once the O-ring seats properly. Now insert this other five millimeter hexagon and it will hold the injector in place. Now, if you look at it from the side, what I did was modify this angle because it was sitting straight before and there's no way the plug could have been cleared. So, fold it up a little bit, that should give us enough clearance.

We have practically achieved it, now what we have to do is adapt it. So you have this length of hose and then this brass adapter. Now let's put this hose on the end of that adapter. What I'm doing here is just stretching it out a little bit so they don't give us a lot of room. Because it's actually too big compared to the one that came out. That's kind of a tight fit there. Then we just need to attach clamps and we are ready to install. The chances of this actually flying off are slim to none without the clamp, but we'll put it in there anyway.

So I think it's 48 psi from the fuel pump in the tank? Last but not least, we have an adapter for our injector. Alright, let's bolt it to the machine. The arrangement they have here, this gasket, spacer, then another gasket and then the inlet itself. So you just sandwich them like this. Stay. All of this goes along with the bolts that held it together from the beginning. When you do this other side, don't forget the little bracket that will hold the airbox in place. And that front latch that was in place doesn't want to come loose now, so we had to put in a shorter one.

Let's make some connections now. Throttle position and air intake, fuel injector. Here we go. Now we go to our fuel line, we just push in and that should let it through. You made a little boo, guys. I actually put the adapter in backwards, so we'll have to take it out of the hose, turn it over, and then reinstall it. Through the magic of editing, this was simply turned around and reinstalled as it's supposed to be. Now here we go. We're going to add a zip tie just to hold it in place at the top along the frame stringer and harness.

Alright guys, we've got our intake mounted, we've got our new injector, our new throttle body, it's ready to go. So let's grab the exhaust and start with that. Let's start by installing our bolts for the exhaust manifold, and the best way I know to do it is to take a couple of nuts and put them facing each other, lock them, and then you can slide them in. Put together this little plumbing puzzle. Take your header and go ahead and place it on the center tube like this. And they want you to use this bolt with this washer and it's supposed to go through here and then go into this existing pickup point where the other exhaust was mounted.

That's not going to make it. So it's too short, I'd say about 10mm. So I'm going with a slightly longer bolt. This is theirs versus mine, so it can bridge that gap. Hopefully you have one of these in your extra screw pile like I do. And at this point, put the exhaust gasket in place. Now let's get it up. Now you want to use the bolts that came out of the original exhaust system. So we have it loose in place, I'll jump to the other side and stretch the spring between the head tube and the midsection.

Now we're going to put the actual muffler on, and because we're using a different set of footpegs from Driven Racing, we have to adapt it a little to fit because we're actually going to be a little short when it comes to going out to the muffler bracket. So I just added a spacer to achieve that and then bought a longer bolt to go all the way through. You just start changing things, this is what you encounter and you just have to find a way around it. Welcome to the world of modifications. I think that will do it, plenty of space between the swing arm, this bolt and the muffler.

So now I think we can start adjusting everything. Let's start with the head tube first, arranging it. After you've ridden the bike for a while, you may need to go back and re-tighten them. As the cylinder head and exhaust gasket expand and contract, a small leak may occur and just needs to be tightened again so it doesn't burn the gasket inside. Let's get that medium support. Last but not least, the rear. And we have one more spring to install. Not that this is going to fall apart, but we want to go install the spring. Now there is one thing left to do.

All this nice, clean stainless steel hasn't been heated yet, but it has fingerprints all over it. So if we run it right now without cleaning it, those fingerprints will get embedded and turn blue and we don't want that. So we'll get some contact cleaner and a towel and wipe them down until they're ready for the first outing. Now let's turn our attention to installing the air box and new filter. With a larger throttle body, of course, we have to adapt to it, starting from the airbox we are going to use. We will then have to modify our existing air box to fit the new tube.

As you can see, it is much larger. So let's take this apart, take out the old tubes and then using a dremel tool, a milling cutter, I'll enlarge them until they fit properly. Just for fun, look at your surface, one compared to the other. I think that's why a little more air will flow, which this machine will need. So let's start by getting this tube extension out of the way. Of course, that's melted into place, so I'll tell you what, we'll just grind it up and then it should release it. If you decide to grind like I did, make sure you get all the shavings out.

We don't want to put that in the engine. In order not to damage the intake air temperature while we do all this, we are going to remove it and set it aside. And then we'll work on loosening that glue, it won't be that hard. No glue in the second. Now all we have to do is make them both fit there and there. What they ask is that this opening be 40.5 millimeters. What I'm going to do is use my gauge to find a socket with a diameter very close to that. A thirty millimeter socket is exactly forty millimeters.

So that will be as close as I can probably get. So what we're going to do is put it in there, score it with a sharp point, and then cut it out by hand. This does not have to be absolutely accurate. Let's do a test fit and see what we have. I like that. I'm pretty sure I have it upside down, but luckily I took a photo before removing the other one so I could put it back at the same angle. Now, for the 50 millimeter, we'll actually see a 36. It's 50.1. Winner. Let me do a little cleaning and then we'll go.

Alright, according to my phone, this one needs to stay here. And then the intake is there. The last word is that we will bring it closer to the machine and see if it correlates. So now that we've pointed it in the right direction, what I'm going to do now is press it all over and apply a little bit of RTV sealant just to make sure that we've sealed it properly because that's the most important one. It is very important that we prevent other particles from passing through where these two meet because they go directly to the engine.

I think that will do. Now let's recover the inlet air temperature. Koso now ships two different foam filters that can be used inside the air filter adapter. I'm going to choose the tightest one, the one that's going to be the most aggressive in terms of filtering everything out. But before I install it, I'm going to open it up and put a light coat of oil on the foam. Combining the foam with a little oil will block most of the dust and particles trying to get in. I'm going to use some PJ1 foam filter oil and I want it on the side that the air will pass through because I don't want to coat it too much.

That should do it. It's not absolutely necessary, but so many years on a motocross track make me hesitant about not greasing a filter before installing it. Now we're going to use the longer screws that Koso sent to reassemble the outer shell. Alright, let's see if we can fix this there. Go ahead and loosen this again and submerge it enough so we can get it in there. There she is. Now let's go ahead and loosen that clamp and place it over the throttle body inlet. Make sure it lies evenly. You should do that. She takes our top bolts, goes ahead and mounts the top of the airbox.

Only 10 millimeters on each side. Alright, now let's work on those throttle cables. So what you want to do is put the top on, the return side first and press it all the way down. And then when you're doing the pulling side, you just want a little bit of slack that you need to bring in before it starts to open up. So a little bit of slack right here and then tighten it up. Make sure it opens completely on its own. Yes, that goes against the stop. That's it, let's take cover again. We need to route the tank vent line back to where it started.

And then we have the crankcase vent line that actually goes to the back of the air box. Alright guys, before I make my typical exit, I need to show you a change I decided to make to the admission system. Once everything was put back together, I had never dealt with the EVAP canister and purge control valve. Now there are a lot of people who just take the system and ignore it. Well, that's not theway I wanted to do it. He just wanted to modify and improve the engineering that came from Honda, and not eliminate anything. So what I decided to do was cut the factory intake just enough that I could remove that brass nipple vacuum and then there's a location on the Koso unit where you can see, well, that's where it should be.

So I drilled it out, transferred it to the new unit, and then put it back together. Well, okay guys, this will pretty much wrap up this video, but we're nowhere near done with this project. All of this new equipment needs to be told how to operate and we will cover that in an upcoming video. Now, if you want to watch that video, why don't you hit the subscribe button? That way, you will be notified when we release it. And once again I want to mention that we are actually giving this one away, so if you check out the link in the description below you can enter to win this exact machine.

Listen, if you have any comments or questions, why don't you go ahead and leave them in the section below and I'll do my best to answer them. Listen, we just want to thank you for shopping here with us at

partzilla

.com and we'll see you in the next video.