Is it easy for beginners to tune an FCR carburetor?

Is it easy for beginners to tune an FCR carburetor?

Is it easy for beginners to tune an FCR carburetor?

I often see on the web that FCR tuning has a wide application range and is easy to tune. In other words, even with rough tuning, it can still run properly. But what about other racing carburetors? How about the CRS carburetor or the TMR?

I've ridden motorcycles equipped with both and didn't need to tune them throughout the year. There were no issues with normal riding. It's not that FCRs are the only ones that work year-round; most carburetors are fine with general tuning throughout the year. The key is how you tune them.

However, it's unclear whether you're truly maximizing the performance of the carburetor. As mentioned above, you can ride throughout the year with just adequate tuning. Beginners probably don't know how to tune properly. I will discuss these points in detail.

So, let's start!

Tuning an FCR Carburetor Easily

If the engine starts, idles, revs smoothly, and reaches 200 km/h, you can say that the tuning is successful. From a fully closed throttle to about 1/4 throttle, adjust the pilot screw and air screw to a slightly rich setting. From 1/4 to 1/2 throttle, you can change the straight diameter, but the initial setting is probably fine. From around 1/2 to 3/4 throttle, adjust the clip position to find a good feeling. From 3/4 to full throttle, adjust the main jet. Changing the main jet from 120 to 130 will alter the air-fuel ratio by about 1.0.

With these adjustments, tuning should be achievable. You can find tuning data by searching the web or asking questions on social media. Many experienced tuners have tried various settings. The factory's pre-tuning might be good enough. As a beginner, if it feels good, there's no need to adjust further.

The basic principle of tuning is comparison, but beginners might not have spare jets on hand. Make small adjustments when you notice issues and revert if it gets worse. Over time, you'll accumulate a stock of jets.

For throttle openings up to 1/4, fixing the pilot screw at one turn out is sufficient. If the air screw feels right with a 15-minute adjustment on each cylinder, that's fine. A lean state will feel weak, even if it revs well. An overly rich state will feel like it's misfiring and not running smoothly.

For initial tuning, refer to the factory settings or tuning data from experienced tuners. These should be close enough for your motorcycle. The main jet shouldn't need much adjustment if it's close to the tuning data. Adjust it only if you really feel the need. Adjust the jet needle clip position about four times to find a satisfying setting.

This is the basic tuning method. Borrowing settings from other motorcycles might not work easily.

Synchronizing the carburetors can be done visually. BITO's display motorcycles are synchronized this way. If you have a knowledgeable rider nearby, ask for some help. Start with your own tuning, not aiming for perfection. That's the first step. As you get used to it, challenge yourself to tune until you're satisfied.

Tuning Becomes Difficult with a Quick Turn Throttle

My CBX1000 is equipped with a quick turn throttle. The throttle angle for full throttle is 56 degrees. When I installed BITO's throttle kit on my CBX1000, the throttle angle was 90 degrees. It's not just the change in the throttle angle for full throttle; the throttle work is entirely different. The effectiveness of the accelerator pump, the revving up, and the tuning itself all need significant adjustments. These are things that can be managed by the rider's feel. However, tuning is easier when the throttle angle is a larger 90 degrees. The drawback is that you can't fully open the throttle with a single operation. An extremely quick turn throttle makes the motorcycle more difficult to handle and the tuning more sensitive and challenging.

When you drastically change the throttle angle, retuning is necessary. In my case, right after installing the quick turn throttle, I just felt something was off. I couldn't pinpoint what exactly was wrong. I learned that even if you don't change the air-fuel ratio, altering just one component can significantly affect the tuning.

What’s the state of perfect FCR tuning?

Perfect tuning cannot be achieved with analog devices like FCRs. However, tuning close to perfection is possible. The tuning that you feel is the best is either the best or very close to it. The best is defined as a state better than the results of any comparisons. The best method is to repeatedly compare to find the optimal tuning. Even if you use a chassis dynamometer to check air-fuel ratios and power for tuning, you still need to compare results to find tuning close to perfection. Easy tuning often means the comparison work is done hastily. It’s possible that the best tuning, as determined by comparisons, might be the one that was done easily. At least if the rider is satisfied, that’s sufficient. If you don’t know what an excellent condition is, it’s not the best, but rather tuning close to the best. Repeat the process of finding tuning close to perfection multiple times. By learning about tuning close to perfection, you will improve your tuning precision. If you repeat the process many times and there’s no change in results, it’s likely that you have achieved perfect tuning.

FCR Beginners – Try Adjusting Just the Screws and Clips

A typical pattern when introducing FCR is having it installed by a motorcycle shop. I followed that pattern as well. Then, suddenly, you start tuning the FCR yourself. For someone who has never touched an FCR before, the first thing to do is to understand the current tuning. The shop should have performed at least the basic tuning mentioned above. They should have left a note about what kind of tuning was done.

For beginners, the easiest way to start and enjoy the changes is by adjusting the air screw. Turn it and observe the changes. The difficulty level is low. Next, try adjusting the jet needle clip. This requires a bit of disassembly but is relatively straightforward and the changes are noticeable.

After that, you'll move on to the main jet and pilot jet, which involves purchasing different jets and possibly removing and reinstalling the FCR. Challenge yourself to do this when you’re motivated.

Is it easy for beginners to tune an FCR carburetor?【summary】

I've mentioned the ease of tuning an FCR. If you have an FCR pre-tuned for your type of motorcycle, you can achieve a comfortable riding state with just a few adjustments. It may not be the best tuning at a veteran level, but if you're enjoying street-level touring, the FCR tuning should be in good condition with a high probability. It shouldn't turn out poorly.

Carburetors that have been left unused for a long time often perform poorly. Gasoline inside the carburetor can deteriorate, causing the jets to become clogged. Achieving the best tuning requires time and effort.

The precision of FCR tuning is somewhat subjective and depends on individual preferences. For me, enjoying the tuning process is a higher priority. Riding a motorcycle should be the most enjoyable experience. I also make an effort not to focus solely on tuning and to use plenty of fuel.

So, everyone, enjoy riding your motorcycles safely! See you again!

CBX1000 Photo Gallery

I'll be posting photos from past logs, including those of changing the FCR jet needle. Adjusting the jet needle is relatively easy once you remove the tank. Conversely, you can also address it by simply removing the FCR from the manifold without taking off the tank.