Rebuilding Carburetors – 1999 Nighthawk 750

Part 2: Carburetor Separation

The carburetors are off the bike – what next? In this post, I will explain how to separate the four carbs from each other and disassemble them so they can be cleaned. FYI, I took the photos while I put them back together – that explains why the carbs are so clean and shiny. They were much (much!) dirtier when I took them apart.

Before you get started, make sure you have the following items:

Carburetor kit

Four carburetor rebuild kits – I bought them online for $16/kit.

Carburetor kit

Cleaning supplies: Simple Green, a can of WD40, at least two cans of carb cleaner, an old tooth brush, a small brass wire brush, and fine steel wool;

The separation process begins by separating carburetors 3+4 from carburetors 1+2. Here’s how you do that:

1. Loosen the four starting enrichment valve arm screws and pull out the shaft:

starting enrichment valve arm screws
Starting enrichment valve arm shaft

2. The spring and three starting enrichment valve arms will come off once you pull out the shaft:

Starting enrichment valve arm shaft and arms

3. Remove the three carburetor synchronization screws and (upper) springs:

impact drill

4. Take off the front bracket and the rear bracket.
In order to ensure perfect carburetor alignment, the brackets are installed with quite a bit of tension on the bolts – I wasn’t aware of this and it took an impact driver to get the bolts out:

impact drill

The impact driver finally got the bolts out – not without stripping two of the bolts – I ordered OEM replacement bolts at (and clearly, this is not my arm …)

The bolts are installed in a very specific order – taking them off in reverse order might make things a lot easier – particularly if you don’t own an impact driver. And make sure you use a screw driver with a large head (#3 works best). This is the reverse order:

front bracket

Same goes for the rear bracket:

rear bracket

5. Once the brackets are off, you can easily pull carburetors 1+2 and carburetors 3+4 apart.
You will end up with two pieces: the carburetor 3 synchronization spring (left arrow) and the three-way fuel joint pipe (right arrow).

front bracket

This completes the first stage of the separation process. Next, separate carburetor 1 from 2, and carburetor 3 from 4.

6. Gently pull each pair apart – you’ll end up with the carburetor synchronization spring (arrow), the thrust spring, the air vent pipe, and the two-way fuel joint pipe.

front bracket

7. That’s it – the four carbs are separated and ready for disassembly. Make sure to keep all those itty-bitty parts and pieces in one safe place. I use plastic containers (preferably with a lid) or Ziploc bags. If you loose any pieces, even just a tiny bolt, you might end up paying an annoying amount of money to replace them. Here is where I would buy OEM replacement parts – I ended up have to replace some of the big bolts I stripped when I tried to remove them in the wrong order.

This useful schematic from the service manual helped me keep track of where all the little parts belong (and, coincidentally, they are numbered in the order of disassembly – No. 1 and 2 are for California Models only, by the way).

In the next post, I will do a step-by-step disassembly of the carburetor itself, clean it and replace some o-rings. And then: put it all back together as if nothing ever happened.

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Rebuilding Carburetors – 1999 Nighthawk 750

Part 1: Carburetor Removal

Most modern bikes are fuel injected – our Triumph Speed Triples are. But the 1999 Honda Nighthawk and the 2004 Honda Hornet are carbureted. Both bikes feature four carburetors (one for each cylinder) … delicate little devils that don’t require any of your attention – until they do.
Carbs like to be synchronized, and eventually, they will demand to be rebuilt.

This three-post series explains how to remove, separate and rebuild the Nighthawk carburetors. Note that no matter how ambitious you are, this usually turns into a multi-day project … though it could be done in a day, I suppose. Make sure to order a rebuild kit (which is basically just a set of replacement gaskets) before you get started. And when I say “a rebuild kit”, I mean: one for each carburetor.
So, in the Nighthawk’s case, I needed four.

In case you’re not sure – the carburetors are tucked in between the air cleaner and the cylinders:


Before you get started, make sure to

a) turn the fuel valve OFF:

Fuel Valve

Sorry, this pic was taken after I removed the tank from the bike – that’s why the background doesn’t look right.

b) and drain the carburetors:

Draining carburetors

When you open the screws (white arrows) about 1/2 to 1 turn, the fuel will start running out of the nozzles (grey arrows) – make sure to catch the fuel with a rag, or better, in a container. The fourth carburetor’s drain screw is on the other side of the bike.

In order to remove the Nighthawk’s carburetors, you’ll have to remove a few other parts first:

  • The seat
  • The side panels
  • The tank: Remove the fuel tank mounting bolt (under the seat) and lift the fuel tank up, disconnect the vacuum tube and the fuel tube, and remove the fuel tank.

Okay, now you’re in business. This is how you remove the carburetors:

1. Loosen all four connecting tube band screws that connect the carburetors with the air cleaner housing:

Tube band screw

When the screws are loose, wiggle the tube bands to make sure they’re loose, too.

2. Remove the four air cleaner housing mounting bolts:

Air cleaner housing

Right side (battery side)

Air cleaner housing


Air cleaner housing

Left side (air filter side)

3. Once these four mounting bolts have been removed, move the air cleaner housing rearward. You might need to wiggle it up and down until the connecting tubes from the air cleaner disconnect from the carburetors.

4. Loosen the four insulator band screws that connect the carburetors with the cylinders:

Insulating band screw

So far, so easy. The next step is where it starts getting a little trickier.

5. You need to disconnect the throttle cables and the choke cable from the carburetor. In order to do that, you have to first loosen the two nuts and the screw that attach the cables to the carburetor brackets:

Throttle cables

Once the cables are no longer attached to the bracket (you can pull the throttle cables out sideways after the nuts have been loosened), you should be able to unhook all three cables from the carburetor. (Disclaimer: I always struggle with this – sometimes it’s easier to leave them attached and disconnect them during step 7)

6. Pull the carburetors rearward while wiggling them up and down until they disconnect from the cylinders.

7. Now that the carburetors are disconnected from the motorcycle, you can pull them out sideways – it’s easier to pull them out to the left side:

Carburetor assembly

It might require an extra set of hands to push tubes and cables out of the way while you thread the carbs out.

8. Congratulations, your motorcycle just gave birth to a 5-pound carburetor assembly!

Carburetor assembly

One last thing, before you start taking the carburetors apart – stick some rags into the air cleaner tubes and tape up the cylinder openings. You really don’t want any dust to get in there, let alone have a mouse move in and make itself at home.

Engine without carburetors

Up next: Carburetor separation and disassembly.

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How to built a paint booth for less than $50

Headlight mask, front fender, and tail section sanded and primed

Last summer, I decided to repaint my Honda CB600F Hornet – I love the matte black but it needed a touch up on the tank (because the factory put the clear coat OVER the decals – so when I pulled them off, you could see where they once were 🙁 ), and the aftermarket front end’s color was off from the rest of the bike.

I had everything I needed for this project: a spray paint starter kit, a bucket of matte black paint, and no clue what the hell I was getting myself into.

Continue reading How to built a paint booth for less than $50

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Light of the wicked – snuffed out

I think this is a bible reference – hope God doesn’t mind. 🙂

This post explains how to troubleshoot a broken brake light.

Today, as I was getting the 2007 Triumph Speed Triple ready for a potential buyer (yes, we’re selling her), I noticed that the front brake wasn’t engaging the brake light. Not sure how long that’s been an issue but I didn’t want to sell the bike with a major safety feature not working properly, so I went into troubleshooting mode.

Triple wiring diagram
Triple wiring diagram

The light itself was definitely working, because it lit right up when I engaged the rear brake. I pulled the tank and the air box to get a closer look at the wires. Multimeter in hand, I incrementally went backwards, from the rear brake light switch towards the front of the bike.

Continue reading Light of the wicked – snuffed out

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Selling the Triple

2007 Triumph Speed TripleYup. We’re selling our black 2007 Triumph Speed Triple.

She’s been a great companion for the past 6 years but it was time to upgrade to the newest model and we’re running out of garage space… Oil, spark plugs, coolant, and tires are new — and the bike comes with the 2013 Speed Triple headlights (check out the pics).

Continue reading Selling the Triple

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‘2 Million Bikers’ head to Washington DC on September 11

Disclaimer: As stated by its organizers, today’s motorcycle rally in DC was politically motivated. Be that as it may, the following article is about motorcycles, not politics.

Flag at the U.S. Dept of Treasury flying at half-mast today

Flag at the U.S. Dept of Trea­sury fly­ing at half-mast to­day

Bikers don’t like to be told what to do and, more importantly, what NOT to do. So when the organizers of the ‘2 Million Bikers to DC’ (2MB) motorcycle rally received a letter from the U.S. Department of the Interior’s National Park Service yesterday, denying them a permit for a “non-stop ride” through Washington DC to commemorate the victims of the 9/11 attacks, they decided to come anyway.

And they came!

Continue reading ‘2 Million Bikers’ head to Washington DC on September 11

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Shining it up!

For this, you’ll need: small pieces of 400, 600, and 1500 grit wet-or-dry sandpaper, a clean rag, some elbow grease and toothpaste.

Yup, toothpaste!

So, I have taken the Hornet apart to paint the tank, headlight mask, and fenders, and in the process, I had to remove the tail light. It’s been sitting on my work bench, staring at me with its hazy plastic lens as if to say: ‘What about me?’

Newfinese road paint
Newfinese road paint

Continue reading Shining it up!

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Day 16/17 – from Missouri to the District of Columbia

So, we’re home.

Gateway Arch in St. Louis

We started west of St. Louis on Day 16, and jumped of the Interstate to have coffee in downtown. I got lost on the way to the coffee shop (I thought I remembered the way from when I was here three years ago) and we had to go by the Mississippi River Front and the Gateway Arch twice. I made it look like that was intended!
The bridge across the Mississippi required some serious adventure bike suspension and tires, which we didn’t have, so we got the bageebees shaken out of us. And it ruined my front tire, thankyouverymuch.

Illinois (and don’t forget to pronounce the “s” if you’re from the Mid-West) and Indiana were boring except for the trees along the road. Trees. Yup. Something to get excited about after riding through the prairie for days.

Continue reading Day 16/17 – from Missouri to the District of Columbia

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