How to Jet a VF750C Magna

Jetting increases the amount of fuel fed to the carburetor.

The Honda VF750C Magna, produced between 1982 and 2005, was one of the most powerful Japanese cruiser-style motorcycles available for several years. In order to boost the power of this motorcycle, you'll have to jet the carburetors and install an aftermarket exhaust system. While you may think that this is an expensive and difficult proposition, the truth of the matter is that most garage enthusiasts can perform a jetting job in their garage in just a few hours.

Things You'll Need

• VF750C Magna jet kit
• Hex wrenches
• 3/8-inch drive sockets
• C-clamp
• Needle-nose pliers
• Screwdrivers
• Drill
• Vacuum cleaner

Instructions

1. Unbolt the passenger seat with a hex-head wrench. When you've pulled the passenger seat off the motorcycle, you will see two bolts that hold the driver's seat onto the motorcycle. Remove these bolts and then remove the seat from the bike by pulling it back away from the fuel tank.

2. Unbolt the fuel tank from the motorcycle's chassis at both the front and rear of the tank. When the bolts are removed from these positions, the tank will slide backward off its mounting rubbers. Clamp the fuel hose with a C-clamp to prevent the fuel from running out, and then release the wire clip that holds the fuel hose onto the engine's carburetor. You can do this easily with a pair of needle-nose pliers.

3. Loosen the compression band that holds the air intake ducts in place over the four intake valves with a flat screwdriver. This will give you access to the butterflies and the carburetor's bowls.

4. Unbolt the carburetor from the engine's cylinder heads, unhook the spring throttle linkage from its assembly, and remove the carburetor in one piece from the top of the engine.

5. Place the carburetor on a flat work surface with the four round tubes with the carburetor's butterflies facing up. Beside these tubes you will see four L-shaped covers. These are the bowls. Remove these covers using a Philips screwdriver.

6. Remove the main jets from the carburetor in each of the four bowls using a flat screwdriver. The tip of the jets is slotted, so all you have to do is turn them counterclockwise and they will come out without trouble. When you have all four of these out, replace them with the jets included in your carburetor jet kit. Tighten them snugly, but be careful to avoid damaging the brass threads by overtightening.

7. Replace the covers to the bowls, and then turn the carburetor over onto its other side. Here, you will see four black tubes down the middle of the carburetor with two round silver covers on each side. This is where the needle for the carburetor will be installed.

8. Remove one of the covers by unscrewing the four Philips-head screws from each corner. Hold the cover down with your finger, because there is a spring just underneath. Gently allow the spring to raise the cover, and then pull it out of the rubber diaphragm.

9. Pull the rubber diaphragm out of the carburetor by first removing the slide at the base of the diaphragm. Accomplish this by threading one of the screws that held the cover on into the center hole of the slide and pulling it out. As you look at the slide, there is only one hole into which the screw will thread.

10. Remove the stock needle and spacer from the slide, being careful to note exactly how they are assembled. First, remove the retaining washer from the assembly with a small pair of needle-nose pliers, and then the rest of the assembly will simply pull apart. Replace the needle with the needle from the carb jetting kit, and reassemble the slide.

11. Look down into the hole in which the slide was located. With the black tubes positioned at 12 o'clock, you will see three holes. One center hole is the needle hole. The other two holes are the jet holes that you will have to drill.

12. Drill out the two holes at the base of the carb slide hole with an electric drill and the drill bit provided with your carb jetting kit. Use a vacuum to remove the bits of metal left over in the bottom of the carb slide hole.

13. Place the slide and the diaphragm back into the carburetor, and then replace the spring and the cover. Perform the same routine on the remaining three covers, and then reinstall the carburetor onto the Magna in the opposite way from which it was removed. Reassemble the remainder of the motorcycle before starting the engine and attempting to ride it.

Tips & Warnings

• Install a high-flow air filter and aftermarket exhaust to match the added power from your jetting job.

References

• "VF750 Magna Jet Kit Instruction Manual"; CobraUSA; 2011