I am the owner of a Honda motorcycle [CBX1000] who lives in Hiroshima City, Japan. I am posting about FCR carburetor and CBX1000 customization. I also post about things other than cars and motorcycles. We will post information that will make bikers around the world happy.
Which racing carburetor should you choose? FCR, TMR, TMR-MJN, CRS, or others…
Points to Consider When Choosing a Racing Carburetor
I will outline the points to consider when selecting a racing carburetor. This is more of a column-like overview. Please note that this information is not based on my personal hands-on experience. I appreciate your understanding in advance.
In addition to the domestic racing carburetors mentioned in the title, brands like Dell'Orto are also available. As I am based in Japan, I prefer Japanese-made products because of their easy availability. Therefore, I will focus on Japanese-made carburetors.
The information I provide is based on rumors and discussions with magazines, online sources, and tuners. Rather than indicating which is best, this might end up being more about the racing carburetors I would like to try.
Here is the order in which carburetors were released:
・New Models: FCR-MX, TMR-MJN, TMR, FCR, CRS ・Older Models: In this sequence. F CR-MX is an improved version of the FCR, modified for motocross with enhancements to the accelerator pump's operation. It is usually available only for single-cylinder engines.
TMR-MJN is based on the TMR, with Yoshimura improving the jet needle. It is possible to convert TMR to TMR-MJN or FCR to FCR-MJN. Essentially, it is a TMR with Yoshimura's MJN jet needle, branded with Yoshimura’s logo and offered in special colors.
There seems to be a package for FCR-MJN, but detailed information is not available online. I view it as a carburetor utilizing Yoshimura’s special jet needle. Changes in anodized color are another difference.
The reason MJN parts are not widespread as aftermarket options might be due to the limited information available or the high cost. The cost of a single jet needle is around 5000 yen, which can be discouraging. Historically, prices were almost double, so for a six-cylinder engine, it would amount to 30,000 yen. In comparison, FCR jet needles are around 800 yen each, which is significantly more affordable.
Another reason for the low adoption rate of MJN might be that it doesn’t always achieve perfect tuning. However, the unique feeling provided by MJN is impressive. I had the chance to ride a CB750F equipped with TMR-MJN and experienced remarkable acceleration.
For my personal choice, if possible, I would opt for FCR-MX, TMR, or FCR in that order. Given that FCR-MX is only available for single-cylinder engines, TMR would generally be the choice. The FCR is widely distributed, which means more information, tuning parts, and custom options are available. It also facilitates easier information exchange if many people around you use FCR.
Additionally, if you are considering a second motorcycle and already have FCR on your main bike, it makes sense to choose FCR for its asset value, including jet parts and other components.
The CRS carburetor also has its advantages.
The FCR is the successor to the CRS carburetor. From a performance standpoint, there’s little reason to choose the CRS carburetor. However, the CRS has a classic look. If choosing based on appearance, a stock carburetor might be sufficient.
In racing regulations where the FCR cannot be used, the CRS carburetor might be selected, possibly due to the presence or absence of an accelerator pump, although the exact reason is unclear. The CRS is generally less expensive compared to the FCR and TMR. Among these, the TMR is the most expensive. When weighing performance against cost, the FCR often comes out on top. Additionally, there seems to be a greater variety of options available for fitting FCRs to different motorcycles. The marketing strategies of manufacturers during the peak of racing carburetors in the 1990s may have contributed to this.
I didn’t fully understand the difference between TMR and TMR-MJN at the time. Magazines often noted that tuning was easier with the FCR compared to the TMR, which made the FCR more attractive to me. The CRS seemed like a cheaper, less refined racing carburetor back then. However, as of 2023, many people prefer using the CRS carburetor.
In 2015, BITO released a new CRS carburetor for the CBX1000. With the advent of the internet, information has become much more accessible, and the proliferation of social media has made it easier to exchange information, contributing to the CRS's growing popularity.
Differences between the CRS and other carburetors like the FCR and TMR include the shape of the slide valve (cylindrical vs. flat) and differences in the slide valve bearing mechanisms. The presence or absence of an accelerator pump and the lack of a pilot screw are also significant differences. Racing carburetors are more about extracting performance rather than increasing it. Peak power is often comparable, but there are significant differences in feel.
In terms of overall performance and functionality, the CRS falls into the next tier. There are various reasons to choose the CRS, such as admiration for racers who used them at the time. However, the era when choosing a CRS simply because it was cheap has passed.
Differences Between Racing Carburetors and Standard Carburetors
A major difference is that standard carburetors are generally vacuum-operated, while racing carburetors are mechanically operated.
Vacuum-operated carburetors use the suction force of the air to open and close the piston valve. In contrast, racing carburetors have a throttle valve that moves up and down in sync with the throttle. This mechanical operation makes racing carburetors suitable for high-performance applications.
Additionally, racing carburetors often come with a wide range of tuning parts and offer high maintainability. For more specific differences, you might want to search for 'vacuum-operated carburetors' and 'mechanical carburetors.
Since I am Japanese, Japanese-made products are easier for me to obtain.
The carburetors mentioned in the title are all Japanese-made.
Regarding parts supply, if you are living in Japan, there shouldn’t be major issues. For FCR carburetors, basic jet parts are generally available online. Slow jets and main jets are easily obtainable worldwide. However, jet needles can sometimes be difficult to source even if you are in Japan. There may be times when they are out of stock. Nonetheless, basic stock is usually replenished quickly to resolve shortages. There might be changes over time.
FCR Beginners’ Guide: Which Racing Carburetor Should You Choose?
The top priority is to choose the racing carburetor that you want to use. Even if you encounter problems, your passion can help you overcome them.
In practical terms, you should prioritize recommendations from people around you or from shops where you can exchange information. Initially, no one is capable of tuning a carburetor perfectly. Having access to information when you’re in trouble is very valuable. Choosing a carburetor with high popularity will ensure that you won’t have trouble with information and parts supply.
Which racing carburetor should you choose? FCR, TMR, TMR-MJN, CRS, or others…【summary】
When it comes to choosing a racing carburetor, the first point to consider is whether a dedicated kit is available. A dedicated kit includes things like whether the carburetor pitch and insulator can be used. While it is possible to fabricate small parts, it is best to have a state where you only need to install it after purchasing.
That wraps up the column on choosing racing carburetors! See you again!
CBX1000 Photo Gallery
I will extract and display photos from past posts that show the FCR carburetor from visible angles.
