Saito FA-100GK

Model Airplane News, Mar 2003 by Jensen, Bill

Displacing the FA-91 & setting a new standard

Over the years, I've flown many 4-strokes, and all were powerful and reliable when operated and maintained properly, but that isn't the main reason I like them; mostly, I just love that 4-stroke sound! Let's face it: a 4-stroke engine has three times as many parts as a 2-stroke and is heavier and more expensive than a 2-stroke of equivalent power. But you just can't beat that great 4-stroke, Harley-like "putta-putt-putt" sound! That its inherent torque advantage allows a 4-stroke to swing a larger prop at lower rpm is a welcome perk, but even without that secondary benefit, I'd use 4-strokes for the sound alone. So when it was time to pick a powerplant for my new Hangar 9 P-51 Mustang, the new Saito FA-100 4-stroke was an obvious choice. For aesthetic reasons, I selected the Golden Knight version for this review.

You can't talk about model 4-strokes without mentioning the Saito brand, which is sold and serviced in North America by Horizon Hobby Inc. I've always been impressed by Saito engines' power, reliability and quality, and the new FA-100 appears to be ready to carry on that tradition. Saito makes only 4-strokes, and they range in displacement from .30 to 1.8ci for single-cylinders to .60 to 4.5ci for multi-cylinders. Saito engines' most distinctive feature is the one-piece head/cylinder design, for which the company claims cooler running, less chance of compression leaks and less weight. Also worth noting is the cast-in, chrome-plated aluminum sleeve and, on all the singles, a reversible carb.

If you haven't owned a 4-stroke, you're missing one of this sport's most satisfying experiences. When I first flew one, it felt a little down on power compared with the 2-strokes I was used to. This was because of its relatively low exhaust frequency, but then a vertical climb almost out of sight erased that perception forever; let's hear it for torque! Early 4-strokes did lack the peak power of 2-strokes, but today's models rival them in many applications.

At first glance, it's apparent that the Saito FA-100 is different from its other single-cylinder stable mates. The cam cover and the crankcase in the cam area have a unique shape. Horizon explains that the new design is part of an ongoing effort to save weight; a similar design is used on certain Saito multi-cylinder engines-the 300 twins and the 170 and 450 radials, for example. The new FA-100 is only 30 grams (1.06 ounces) heavier than the FA-91's but a whopping 350 grams (12.3 ounces) lighter than the FA-120's. That's only a 6-percent weight increase compared with the 91, but the FA-100 produces 13-percent more power.

As previously stated, I tested the FA-100 Golden Knight (GK) version. Saito offers all of its engines in standard natural aluminum and as a GK version, Which has a glossy black finish with "golden" valve covers. The GK option is purely cosmetic and offers no advantage beyond style.

HOW IT STACKS UP

The FA-100 does not fit the same mount as the FA-91 or the FA-120; it has its own mounting-bolt pattern. It isn't a remake of an existing product; it's a new design, and most of its dimensions fall between those of the .91 and the 1.20, with the exception of the distance from the prop-drive washer to the back of the carb, which is about the same as on the .91. I've compared all the dimensions, and it's obvious that this engine could easily be used in .91 4-stroke planes.

ON THE BENCH

Like many of today's engines, this Saito could have been flown right out of the box without bench running. I ran it on my test stand to become familiar with it and to make approximate carb settings before I mounted it in my new P-51. After I had set the needles, the engine was very friendly in all respects-easy to start, idled well and had great throttle transition from extended idling to full power. The owners' manual gives detailed break-in procedures both for on the bench and in flight. Always read and follow all the owners' manual instructions. The Saito's manual recommends a fuel nitro content of 10 to 15 percent. Horizon promotes the use of 30 percent, claiming more power and smoother running. I have run from zero to 30 percent nitro without a problem, but I've settled on 15 percent as a good compromise. I fly all kinds of models and find that I can run just about anything on 15 percent, including 2- and 4-- strokes, .15 to 1.80 sport planes, Quickie 500 pylon racers and .60 hells. Using only one fuel type for all my models is a big convenience!

* Props. For the first flight in the Mustang, I used an APC 14x8 turning 9,600rpm at peak and backed off to 9,300rpm for flight. There are many available props for this engine. As a rule, I just keep the wide-open static rpm at between 9,000 and 10,000. I had hoped to run a 4-blade prop on the Mustang, but APC says 2-blades are much more efficient, and besides, I haven't yet found a 4-blade that revs within the engine's rpm range.

* Installation. Most 4-stroke engines have the carb at the rear. This can complicate the throttle linkage hook-up because the carb is often too close to the firewall to allow a nice bind-free connection. I just extend the throttle rod past the carb arm, make a 180-- degree bend and use a standard nylon clevis. Another method is to install a 4-stroke linkage kit that uses a nylon lever; several brands are available.