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:
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:
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:
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:
Right side (battery side)
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:
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:
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:
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!
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.
Up next: Carburetor separation and disassembly.