The Honda Ruckus Carburetor: Keihin NVK

The Honda Ruckus Constant Velocity Carburetor

The Honda Ruckus has been around since 2003 but the one thing that has been constant is that it uses a carburetor instead of fuel injection. Fuel injection has been a recent change in scooters, but even though the 2012 Honda Metropolitan is fuel injected, the Honda Ruckus is still using the Constant Velocity (CV) carburetor. Why is the CV Carburetor still used and what kind of Ruckus parts can we use to make it work better?

The Constant Velocity Carburetor is the OEM carburetor in the Honda Ruckus. It is made by the Japanese vehicle engine management company, Keihin, who has been in business since December of 1956. It started out as an automobile parts repair and processing facility and it wasn’t until September of 1957, when they started producing carburetors for the Honda Dream motorcycle and Fuji Heavy Industries Rabbit scooter. The carburetor model for the Ruckus is the NVK, but does use Main Jets for the FCR Carburetor. The FCR is a variable Venturi carburetor and not the same as the NVK, it is just that the Main Jets are. The Slow Jets come from a DVK Carburetor that is in Kawasaki V-Twin ATVs like the KFX-700 V-Force, which is a CV Carburetor and it may be a deviation of the Keihin CVK. It, however, does not use the same Main Jet as the FCR or the NVK.

Tuning the Ruckus carburetor is the same for any CV, Variable Venturi, or Fixed Venturi carburetor; you use the Plug Chop method and change your air/fuel mixture screw and main and pilot jets to tune accordingly. The only issue that arises is the difficulty to procure main jets at the time of this article. Keihin, for a reason not given to us, has not produced enough jets to keep up with demand. It is entirely possible that the main cause is a switch by many motorcycle manufacturers to fuel injection. As stated before, Keihin is an engine management company; which means they also manufacture ECUs, fuel injectors, and other EFI (Electronic Fuel Injection) components. With the Metropolitan and Zoomer, the overseas name for the Ruckus, becoming Fuel Injected bikes, the demand for jets for the NVK carburetor is down in demand except for here in the North American Continent where the Ruckus is still a carbureted bike.

So, what can be done? There isn’t much, sadly I must report. Until those jets are produced by Keihin or another aftermarket manufacturer, there is not solution except custom modification. This means finding ways to shim the needle and/or opening or closing the main jet for the perfect fueling. Shimming the needle wouldn’t be too difficult and is easily reversible; however modifying the main jet would not be easily reversible. While we do not recommend, and highly request that you do not, do this modification, you can use solder to close up a main jet and drill it out to enlarge it. Again, we do not recommend this modification as once you perform it, you will never get the jets back to the way they were. Shimming the needle is easy and can be undone; the problem lies with finding a shim thin enough to work. Brass washers are very thin and could work, but I have no data to confirm this other than knowing this is how Harley Davidson CV carburetors are modified. They also use a Keihin CV carburetor, but the CVK is not the same as the NVK.

Honda Ruckus Essential Tools

Many people go buy a Honda Ruckus scooter and take it to the dealer for repairs or service to find out that dealer just charged them $90-110/hr for labor. That wallet shock has lead to many scooter riders to become scooter experts when it comes to their repair and service needs. Unfortunately they also find out the hard way on what tools they really need. This guide will take you through some of the Ruckus parts and tools you really need to make sure your next service doesn’t cost you much money or much time waiting on parts. Not only will you be able to work on your Ruckus, but you’ll become more familiar with it, too.

One of the very first things you should pickup is a Honda Ruckus service manual for your year Ruckus, though most manuals go from 2003 to present Ruckus scooters. You will want to get the Honda made service manual, the very same one Honda Motorcycle technicians use. Typically, most aftermarket manuals can miss a detail or two that can be required to know. This isn’t always the case, but it is always better to have the factory manual. These can be purchased at your local Honda Motorcycle dealer or at some of your local scooter stores. What is really nice about the Honda Factory manual is that it will show you the proper way to route cables so that it not only goes back in the factory position, but they will also be easier to deal with.

The next thing to make sure you have is a decent set of hand tools, which include socket wrenches, open-end/box-end wrenches (the wrench most people typically think of when you say “wrench”), screw drivers, pliers, and an adjustable wrench. When you do pick up your socket and open/box wrenches be sure they go from 8mm to 17mm, as these are the typical sizes of bolts and nuts on your Ruckus. A quarter inch drive socket set is a great starting point and will usually have socket sets in the 8mm to 21mm sizes. It’s big enough for good torque, but small enough to reach most anything on the Ruckus. However, if you are not careful it can still break a bolt or stud if you over tighten them. An eighth inch drive socket wrench is great for smaller bolts and nuts and tighter places, but there isn’t much on tight spaces on the Ruckus considering how open it is. You don’t have to necessarily splurge on Mac or Snap-On hand tools, as ones from Craftsman, Northern Tool, and Harbor Freight are of very good quality, too. Most all hand tools carry a lifetime warranty on them as well, so if they break, you can get them replaced.

There are a couple of final tool types to have that can be essential, the torque wrench and a good digital volt and ohm meter (also known as the DVOM). These are two tools that you should spend on getting excellent quality and will be something you want a name brand on. However, just like many things, price does not always guarantee quality but it is a good reference. You want to try and get two different torque wrenches: the inch-pound and the foot-pound. You’ll use the inch-pound on the smaller bolts and nuts while you will use the foot-pound on larger ones. The DVOM is essential to have because of the electrical parts you can run into on the Ruckus. You’ll want to also be sure that your DVOM can do AC (alternating current) and DC (direct current) power. Alternating current will come from your stator and charging system. Direct Current will come from your battery. The DVOM will allow you to check for things like open circuits (broken electrical wires or blown fuses), resistance, current, and voltage. Also learn about voltage drop as that can solve a majority of electrical issues on your Ruckus battery, especially on things like battery drain on a parked scooter.