Tuning Journey Shadow 600 vlx 1992 dual carb

Solomon New Member
10/12/26, 12:42 PM
I'm Solomon from Amsterdam, the Netherlands, and this is my hawg.

I've been wanting to build a chopper for as long as I can remember. There's just something about a proper chopper that does it for me. And after turning 24, I figured it was finally time to stop dreaming about it and start wrenching.

The only problem? The bikes I REALLY want, a Dyna or a Buell Super Cruiser, are financially fucking stupid purchases for a freshly graduated student who just started working. So instead of going broke trying to buy someone else's dream bike, I've decided to turn my old lady into the chopper I've always wanted.

I bought TJBC velocity stacks and a performance rebuild kit. But much to my dismay, when I tried to get my hands on some upsweeps (exhaust), I found out that I couldn't BUY these parts because I live in the EU. A place that hates anything with a gasoline engine. Blah blah blah, I'm not allowed to buy it.

Very well. After some digging around, I found PTW Custom Shop, based in Poland: https://ptwcustomshop.com/products/custom-exhaust-honda-shadow-vt600-upsweep

The website seemed kind of sketchy, ngl. But I bought them anyway, and they eventually came in. They took long asf to arrive, to be fair. Nearly a month and a half, almost. But they came in. Beautiful stainless steel exhaust pipes, the welds look great, and they look sexy!

The TJBC shit came in as well. But goddamn, shipping is expensive. Still, I had set my mind on this whole chopper thing.

I wake up one morning, check my mailbox, and find an email from DHL or UPS (doesn't matter). With my eyes wide open, I read the message. I have to pay nearly 115 euros in import taxes, tariffs, and whatever the fuck else they charge you for. Making this whole thing a bit more expensive than I had planned.

But I have the exhaust and everything else, and I've already planned a day to work on it with my old man and my uncle. I'm knee-deep in this shit, so I pay the 115 euros.

But awesome, all my shit has finally arrived, and it's time to get this thing started!

1/10/2026

Originally, this whole project started because my valve cover gasket was leaking like CRAZY. I was wiping oil off the cylinder almost daily and constantly having to top up the oil. It genuinely felt like I was wiping my bike's ass.

So naturally, I talked myself into buying a bunch of other shit as well. Since replacing the gasket meant taking the carbs off anyway, I figured I might as well install some velocity stacks and a performance rebuild kit while I was at it.

We start by removing the exhaust, throwing away some now-unneeded parts, and angle-grinding off my passenger pegs because they're in the way of the upsweeps. Then we tackle the airbox, which comes out with some difficulty. There are a TON of hoses and little bits and pieces that, according to the YouTube videos, I can get rid of.

Eventually, we get everything disconnected from the carbs and manage to get them out. While we're doing that, my dad gets started on installing the new exhaust (yes, we had new gaskets). I forgot to bring the bolts for the upsweeps, but thankfully, my uncle had some lying around. Thank god.

Exhaust is on, and it looks SWEET.

Next up, the carbs. Everything goes pretty smoothly, with no major complications. One thing that did catch my attention was the float bowl gasket. That thing was FUCKED. Hard as hell, crushed to shit, and somehow still managing to seal.

We disassemble most of the carbs and get to work cleaning everything. Looking back, we forgot to remove the needle holder that sits in the venturi for cleaning, but we did put the disassembled carbs through an ultrasonic cleaner.

Anyways, here's the important part.

We put the exact same setup in both carbs. Any fine-tuning regarding which cylinder might need a bigger or smaller jet (since one of the upsweeps is considerably shorter than the other) was something I decided to save for later.

145 main jet

45 pilot jet

1 shim on both needles

Now it's time to put her back together. My dad puts hoses on the brass nipples between the dual carbs AND on the black plastic nipples (the sub-air breather vents). And somehow, she starts up.

JESUS CHRIST, THIS THING IS LOUD.

I had ordered the exhaust with DB killers, but... there's no fucking way I'm driving around Amsterdam like this without getting arrested. The sound is super cool, though. That beautiful reverberation coming from the upsweeps, and the engine just purring like a wildcat. Absolutely fucking awesome. But way too loud, so I ordered some fiberglass wool, and my dad was gonna get me some of that 2000-grit steel wool from his job.

Anyways, she runs, but she doesn't run very well. Aside from that, the pressure of the exhaust pulses when giving it gas doesn't seem equal between the two exhaust pipes. Thirdly, there's black smoke coming out of the exhaust, and it's also building up on the inside of the pipes.

Now, from everything I'd watched on YouTube to prepare for this job, this looks like an engine running way too rich. That's what I tell my old man and uncle. They say I can't know for sure and that we should check the spark plugs as well, but I'm convinced it's running way too rich.

We get her to idle pretty nicely. Almost perfectly, tbh. They tell me to take her for a spin.

I'm all excited. Could I actually get this whole tuning thing sorted in one go? Fuck, I'm so excited.

I roll out of the garage using a tiny bit of throttle and mostly clutch. I get out onto the street, and okay, she might be running too rich since she's not pulling super well, but I could probably tune that out.

I crack the throttle past 25% and...

WTF.

The motor just... stops combusting or something. It just goes quiet. But when I roll the throttle back to around 25% (the pilot stage), she picks up again.

I quickly turn around, defeated, knowing there's still a bit of work to do regarding the tuning.

We close up shop for the day since the sun's gone down. Me and my dad head back home from Gouda to Amsterdam leaving my bike back at my uncle in Gouda

4/10/2026

Sunday, day of the Lord.

This time, my dad isn't coming with me since he doesn't feel it's necessary. I've done some digging around, and my hypothesis that the bike is running way too rich is probably right. Besides that, I've been using AI and these forums to get answers to some questions I had.

I still had those air-fuel mixture screws lying around since I hadn't installed them during the rebuild. From what I'd looked up, there was a possibility that an aluminium cap MIGHT be covering the OEM mixture screws, meaning I'd have to drill into my carbs to get to them. I was honestly a bit worried about that.

Thankfully, when I arrive and check the carbs, the OEM screws are uncapped. No drilling required! We unscrew them, take out the springs, washers, and little rubber O-rings, and install the new mixture screws.

Besides that, we also fix a coolant leak coming from the connecting pipe between the two cylinders. We flush the system and refill it with fresh coolant.

Now, regarding the carbs, we decide to TAKE OFF the hoses connected to the brass nipples and the black plastic nipples (the sub-air breather vents). Mind you, these hoses were looped, meaning one sub-air breather vent was essentially connected to the other.

We start her up, and BOOM! She fires up with the first crackle of the starter.

It's 21°C outside at this point, and I feel like I should at least need to pull the choke out a tiny bit. But nope, she just fires right up.

Me and my uncle put our fingers over the sub-air breather vents, and guess what? The bike starts bogging down and will eventually die. So, yeah, we definitely leave those hoses off.

She idles better, and the exhaust seems to be producing less black smoke. Sounds good. Let's go for a test ride!

Oh, and I almost forgot to mention: we stuffed a good amount of 2000-grit steel wool into the exhausts. And WOW, it definitely makes the pipes quieter.

There's just one problem. The rear cylinder's exhaust, the shorter of the two pipes, spits the steel wool straight back out after about 30 seconds. Okay, well, that sucks. Now I've got to figure something out for that. So one exhaust still has steel wool in it, while the other doesn't.

Doesn't matter. Me and my uncle head out for a ride.

She definitely runs a bit better. I'm getting hopeful because the throttle response in the pilot stage feels improved. There's still more to gain, though.

So I crack the throttle past the pilot stage, and... well, there's definitely combustion happening this time. The problem is that when I go from the pilot stage, around 25% throttle, into the range where the jet needle starts taking over, the RPMs drop. It's almost as if the exhaust gets a bit louder, too.

At certain moments, though, she actually wants to give me some power. It's like she's teasing me with what she COULD be doing.

The idle isn't quite right either. The RPMs keep wandering around, almost as if the engine is searching for a particular RPM to settle at but can't quite find it.

Eventually, we head back because I've noticed that I just can't give her throttle and expect her to respond properly.

And once again, I'm assuming she's running too rich.

It's getting late again, so we head back to my uncle's place, and I make my way home.

Another day of wrenching, a few things improved, but the mystery of why this thing won't run properly is still very much alive.

145 main jet, 45 pilot jet, 1 shim on the tjbc diaphragm/needle. and pilot screws set 2.5 turns out.

11/10/2026

My uncle doesn't have a lot of time to wrench today, so we get straight to work.

Once again, I've been doing my research at YouTube University and using AI to help me figure out what might be going on. At this point, I want to stop blindly changing things and actually work through the possible causes. The suggestions are to check the spark plugs, inspect the float levels, and make sure both carb slides are sitting properly and moving freely at the same speed.

First up, the slides. We check both slide assemblies, and honestly, they look fine. They're seated properly and seem to move at pretty much the same speed. Nothing obviously wrong there.

Next, the spark plugs.

WOW. One is covered in black soot, and the other is covered in black soot as well, but it's also wet and smells like gasoline.

Right. I'm thinking she's running a bit rich.

Before we get back into the carbs, we also make another attempt at quieting down the exhaust. We replace the steel wool with fiberglass wool, hoping it'll do a better job of keeping the noise down.

We also revisit the hoses on the sub-air breather vents. I want to route them somewhere they won't be affected as much by turbulent air, so we run them towards the neck of the bike, near that little white plastic triangular overflow thing.

Alright, time to fire her up and see what happens.

She starts up and runs... decently.

Suddenly, my uncle goes, "STOP, STOP, STOP!"

WTF is going on now?

We forgot to put the black caps back on the spark plugs. Fucking hell. We put those back on, fire her up again, and, of course, she runs WAY better now.

While she's running, we notice that the rear cylinder's exhaust (the shorter of the two pipes) starts spitting out the fiberglass wool. The other pipe doesn't. Great. So much for that solution.

With the basic checks out of the way, I want to have another look inside the carbs. My uncle doesn't have much time today, but since we're already wrenching, we decide to pull them off again.

My plan is to remove the shim I'd installed under the needle and properly inspect the slide assemblies while we're at it. My uncle suggests that we might as well change the main jets from 145 to 142 while the carbs are off.

Sure. I'm not going to argue with my uncle's wisdom.

We take the carbs apart and inspect the slides. Everything looks fine, nothing damaged. We pull out the needles, remove the shims, and carefully put everything back together. We also swap the 145 main jets for 142s.

For reference, the setup is now:
- Pilot jet: 45
- Needle shims: 0
- Main jet: 142
- Air-fuel mixture screw: 2¼ turns out
Carbs reassembled, back on the bike, and time to fire her up.

I hit the starter, but she doesn't really want to turn over properly.

And once again...

"STOP, STOP, STOP! THE FLOAT BOWL IS LEAKING!"

I look over the bike, and yeah, the float bowl is leaking like CRAZY. Gasoline is just pissing out of it.

We get the carbs off within five minutes at this point. We're getting pretty good at this shit, almost like a pit crew.

We open her up, and the float bowl gasket from the TJBC rebuild kit has expanded from absorbing gasoline.

FUCK.

How the hell are we going to get this thing to seal again?

We somehow manage to finesse the gasket back into place with some delicate fingering work and a bit of liquid gasket. Cool. Let's get it back on the bike.

Five minutes later, the carbs are back on. Like I said, we're getting good at this.

I hit the starter, and...

Uhh... fuck. That doesn't sound good.

I've never heard my bike make noises like this before. The battery clearly isn't happy about all this cranking without getting a proper ride to recharge it.

Fuck. What now?

We try again, but the starter is making it VERY clear that we need to stop. Instead of cranking every half second, it's now struggling to turn the engine over every two seconds or so.

We call it.

My uncle suggests we have some coffee while he hooks up a battery trickle charger. So we drink our coffee, give the battery some time to recover, and come back to see if we've got enough juice to try again.

Thankfully, we do.

We start her up inside the garage, giving the starter a few cranks to get the gasoline flowing into the carbs, and there she goes.

She idles BEAUTIFULLY. but i didn't need to pull a choke when it was 15c outside so im still feeling it is a bit 2 rich

We turn her off and get ready for a test ride. The tank goes back on, and we put the seat on without screwing it down. We roll her outside, I hit the starter, and BOOM. She fires right up on the first crank.

Awesome.

We're running out of time, and my uncle has to leave. But I can still take her for a test ride and ride her back into the garage while he's gone.

So, here's the setup I'm taking out for a spin:
- Pilot jet: 45
- Needle shims: 0
- Main jet: 142
- Air-fuel mixture screw: 2¼ turns out
- Exhaust: One pipe packed with some fiberglass wool, the other basically free-flowing
I roll out of the garage, and she feels a bit more eager than last time. Could be the mixture screws, could be the jetting, who knows.

I crack open the throttle, and the pilot stage actually feels pretty good. Definitely not perfect, but we're moving in the right direction. I can feel that she likes this setup a lot more than when I had one shim installed.

Even in the higher throttle ranges, she's responding properly now. Second and third gear seem to respond best to throttle input.

In my inexperienced opinion, she's still running too rich. But the difference is pretty fucking massive.

I'm cruising at 60–80 km/h without too much trouble. A week ago, I couldn't even get her to pull properly at 40–60 km/h. This is great!

Okay, let's try WOT.

Well, she doesn't seem to like that very much.

The more throttle I give her, especially when I snap the throttle open as I get into what I'm assuming is the main-jet range, the more she starts sputtering and climbing in RPM rather than bogging down like she did before.

I don't investigate it much further because, honestly, I'm just happy the bike is running better than it was.

I can get her up to around 90 km/h pretty comfortably now. She's still WAY too loud, but at least she's finally running well enough to ride.

Unfortunately, I don't ride her home that day. I came to my uncle's place by car, so I'll have to come back tomorrow and pick her up.

But for the first time since starting this whole project, I'm actually feeling pretty hopeful.

12/10/2026

I take public transport to Gouda to pick up my bike. I pack all the stuff I need from my uncle's place, including the fenders and other bits and pieces, and get everything ready to go.

Before setting off, I fill her up and adjust the air-fuel mixture screws. I turn them in a quarter turn, bringing them from 2¼ turns out to 2 turns out.

Alright, time to fire her up.

She starts almost instantly. Still loud as hell, but idling nicely. The idle seems a little high right now, but since the engine is still cold, I'll wait until she's warmed up before adjusting it. I've got about an hour of riding ahead of me to get back to Amsterdam, so that'll give her plenty of time to warm up.

Nothing to it but to do it.

I get on and take off.

With the hoses routed to the sub-air breather vents, the mixture screws set to 2 turns out, and NO needle shims, the motor seems to be running better. I DO still have the original carb boots installed, which have presumably been on there since 1992. I've got new ones ready to go, but we didn't install them during the rebuild. That's still something I can do later.

For now, I'm riding with the current setup, and honestly, it's not going badly at all.

She still feels a bit too rich, though. At least, that's what I'm thinking. When I give her some throttle, I get the feeling there's more power to be unlocked. Whether that's actually a rich mixture or something else, I can't say for sure yet.

Another reason I'm suspicious is the fuel consumption. I check the tank and notice that she's definitely sipping a bit more gas than I'd expect. Then again, I haven't measured the consumption properly, so that's just an observation rather than proof of anything.

Back to the ride.

She pulls pretty decently when I give her some throttle in first, second, and third gear, even before she's fully warmed up. Eventually, I reach the highway.

I need to merge, so I start building up some speed, and she's responding nicely. The jet needle range still feels a little off to me, but she's running well enough to get up to speed. I shift into fourth and reach 100 km/h, which isn't bad at all!

However, I feel like I'm asking a lot from the bike here.

When I give her more throttle, which I assume puts me further into the jet needle and main jet ranges, she doesn't really accelerate much faster. The engine gets louder and the RPMs climb, but the speed doesn't increase as quickly as it used to when the bike was completely stock.

I'm not entirely sure what's happening here, but something doesn't feel right. I'm twisting the throttle further, the engine is clearly responding, yet I'm not getting the acceleration I'd expect.

By this point, I'm on the busy Dutch highways, riding like a bitch because I can only comfortably maintain around 100 km/h. I don't feel like I have much extra oomph available if I need to accelerate out of a sticky situation.

The maximum speed I can really get to is around 110 km/h. More importantly, the acceleration from 80–90 km/h up to 100–110 km/h feels noticeably slower than it did when everything was stock.

Naturally, I'm still thinking the mixture is too rich, although I know I haven't actually confirmed that. I could check the float bowl fuel levels, but we installed new TJBC float needles and needle holders, so I'm not immediately convinced that's the issue. Of course, new parts don't automatically mean everything is adjusted correctly.

One thing I also forgot to test was whether pulling the choke slightly would change how she responds. That might have helped me figure out whether the mixture was actually too rich or too lean in that throttle range.

Anyway, back to the ride.

Everything goes pretty smoothly for a while. No major changes, no sudden problems. Just me and my loud-ass chopper making our way back to Amsterdam.

But as I get closer to home, something changes.

The bike starts responding to the throttle better, almost as if some miracle has happened and the richness problem has suddenly improved. Maybe the engine is finally properly warmed up. Maybe something else is going on. I honestly don't know.

I'm nearly home now, so I decide to give her one last proper test at WOT before parking up, so I can check the spark plugs afterwards.

And WOW.

I can't remember for certain whether I was in first or second gear, but I think it was first. I open the throttle all the way, and the bike suddenly pulls HARD. She gets to 50–60 km/h ridiculously quickly.

But this also leaves me confused. Earlier in the ride, opening the throttle further didn't seem to translate into much more acceleration. The engine would get louder and the RPMs would climb, but the speed wouldn't increase proportionally. At WOT, however, she suddenly seemed to pull much harder.

I still need to test this properly, because I haven't figured out exactly what's happening. I also forgot to test whether applying a little choke would change the way she responds.

For now, I'm just happy that she seems capable of pulling properly under certain conditions. The question is why she doesn't do it consistently.

By the time I get home, I'm pretty happy with how things have gone. She's definitely not perfect, and I still need to figure out what's happening at higher throttle openings,

i park the bike in my front garden

Then I notice something.

There's a single drop of yellowish liquid on the case that sits under the engine. My first thought is coolant, but the new coolant I put in is red...

Hmm.

I take a closer look around the bike and notice that one of the fuel hoses, the one with the metal coil wrapped around it, is wet. Upon further inspection, I discover that one of the carburettor float bowls is leaking slightly.

Interesting.

Could that also explain some of the fuel consumption? And could the leaking float bowl have something to do with the tuning issues? I don't know yet, but it's definitely something I need to sort out before doing any more testing.

So, here's the game plan for the next round of wrenching:
- Buy two new float bowl gaskets to replace the ones that have been giving me trouble.
- Consider trying a smaller main jet, going from a 142 to a 140.
- Replace the old, presumably 1992-original carb boots with the new ones I've already got.
- Investigate the high-throttle behaviour properly instead of just assuming everything is running too rich.
My current setup is:
- Exhaust: PTW Custom Shop upsweeps, essentially free-flowing with some fiberglass wool packed inside.
- Intake: TJBC velocity stacks.
- Main jet: 142.
- Needle shims: 0.
- Pilot jet: 45.
- Air-fuel mixture screws: 2 turns out.
I'm also wondering whether I should change the pilot jets from 45 to 42, but I'm not going to start throwing more parts at the problem without figuring out what's actually going on first.

For now, I'm just happy that the bike is finally getting somewhere. She's loud way too loud for the dutch DB limits I'm thinking, still needs work, and clearly isn't running perfectly, but at least I'm starting to see some progress.
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