RCU Review: RCGF 120cc Twin Cylinder Gasoline Engine Part 2

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    Contributed by: Geoff Barber | Published: November 2015 | Views: 13160 | email icon Email this Article | PDFpdf icon
    RCUniverse.com Review of the RCGF 120cc Twin Cylinder Gas Engine - Part 2 - Performance Report
    Geoff Barber

    Email Me

    4029 E. Golden Acres Drive,
    Sierra Vista, AZ. 85650
    Email: rcgfsale@zjrcgf.com


    It seems as though there's a lot of competition in the gas engine market these days, and there are a few names that everyone is familiar with. Some of the big ones are DA, DLE, and 3W - just to name a few. There's more to the gas engine game than just them! Over the past decade, several smaller companies have sprung up - some have stayed, and some have gone away. But, just because these smaller companies may not be as well known, doesn't mean they don't have good products at good prices!

    RCGF, a Chinese manufacturer of gasoline engines, designs and manufactures engines specifically for the RC aircraft market. They have a line of gas engines as small as 10cc, all the way up to 120cc! In addition to the vast size range, RCGF has a number of twin-cylinder engines as well - 20, 30, 40, 60, and 120cc - all are a 'boxer' type, meaning the pistons travel in opposite directions to minimize load and balance concerns. This, in turn, also reduces vibration.

    While RC gas engines have been around for quite a while, the demand for high quality twin cylinder variants is fairly recent. But these twins have come a long way in a short time! The RCGF 120cc twin is relatively new on the market, but definitely fits the 'high quality' definition.

    So, let's open the box and see what's inside!

    • Specifically Designed for RC Use
    • Two Year Limited Warranty
    • 'Boxer' Design Reduces Vibration
    • Single piston Ring Design
    • Narrow over-all Width
    • Walbro Pumped Carburetor
    • Lightweight Ignition Module
    • Standoffs and Radial Engine Mount Included
    • Excellent Customer Service!

    • Engine Quit During Flight - See Performance Report

    Skill Level:

    Time Required to Build:

    Frustration Level:

    What do these ratings mean?

    Name:RCGF 120cc Twin Cylinder Gasoline Engine

    Price: $689.99 (Accurate at time of review)

    Engine Type: 2 Stroke Gasoline Engine
    Cylinder Displacement: 120cc (7.2 ci)
    Weight with Ignition and Mufflers: 2830g (99 oz)
    Weight w/o Ignition and Mufflers: 2450g (86 oz)
    Bore x Stroke: 47mm x 35mm (1.85 in x 1.37 in)
    Carburetor: Walbro

    Ignition: DC-CDI (Computer Controlled, Auto Advance, Electronic Ignition System)
    Power Supply: 4.8 - 8.4 Volts
    Speed Range: 1500-9000 RPM
    Recommended Fuel Ratio: 25-40:1 (ashless 2-stroke oil)
    Recommended Propellers: 28x10 29x9 Two Blade

    So here's a quick recap in case you missed the first part of this review. The RCGF 120cc twin has been installed in my World Models 30% PT-17 Stearman. The installation was straight forward, and presented no issues. All of the included accessories made installation easy! I really liked that RCGF even included a propeller drill jig!


    After completing the remaining assembly of the Stearman, I secured the plane's tail and started the break-in procedure. I filled the Stearman's 1500cc fuel tank with fresh fuel (91 Octan non-ethanol gasoline mixed at 30:1 with ashless, two-cycle oil for air-cooled engines). With all the batteries connected and switches powered on, I closed the choke, advanced the throttle slightly, and started flipping the 27x10 Falcon propeller. Because of the fuel tank's location, it took quite a few flips of the propeller to get fuel to the carburetor. When the fuel did finally reach the carburetor, the engine fired almost immediately. I opened the choke, flipped the prop a few more times, and the engine started and stayed running at a high idle. My first thought was that I really liked the low, throaty sound coming from the twin mufflers!

    I let the big-block twin warm up for several minutes before setting the high-idle to 2500 RPM. RCGF recommends running their engines at this speed during break-in. My 120 twin ran at this speed for 20 minutes before I started made any other throttle changes. After that first 20 minutes, I began running the engine at varying speeds ranging from a low idle (it easily ran at the recommended idle of 1500 RPM) all the way up to short bursts of wide open throttle (running the Falcon 27x10 Civilian prop, the 120cc twin made 6900 RPM). In total, the first tank of fuel took nearly 30 minutes to run through the engine!

    For the flight test, we had a great day - 70° F, 3-5 MPH winds, and a sunny sky! Once again, I started the 120 twin (it started MUCH easier this time) and let it warm up for several minutes. When we had clearance from the field boss, the Stearman was taxied out to the grass strip and readied for take-off.

    The throttle was advanced and the engine came alive - the familiar throaty rumble from the mufflers signified that the engine was running fine and the large biplane took off without incident. The RCGF 120cc twin and Falcon 27x10 Civilian propeller proved to be a perfect combination for the 40 pound Stearman!

    For most of the time that the Stearman was in the air, the engine was running at or under half throttle - the 120 has A LOT of power! The engine sounds great in the air as well!

    Unfortunately, we did run into some trouble on the maiden flight. About seven minutes into the flight, the engine began to run a little rough. We set the Stearman up to land, and when the throttle was brought back to just above idle, the engine quit. Thankfully, the large biplane glided in without incident, and touched down with just a slight bounce.

    We rolled the Stearman back to the pits and began to investigate what had happened to the engine. To make a long story short, the 120cc twin did not have enough lubrication and ended up scoring both pistons and cylinders. That, was the bad news. . .

    After sending RCGF a few high-resolution photos and a couple of emails, they sent out a new, complete, engine! That, was the good news!

    I looked over the new engine, and I saw a difference - the new engine had a different carburetor mount and carburetor. The original carburetor had a throat that was 28mm in diameter. The new carb's throat was only 22mm. The throttle arm on the new carburetor was slightly less user friendly, but I was able to use a DuBro 2-56 ball link and pushrod to make the connection to my throttle servo.

    Unfortunately, fall quickly changed to winter and I was unable to get the Stearman back in the air. However, I did have just enough time to get the new engine broke in on the ground - the new engine ran just as good as the original, if not a little better - even with the smaller carburetor!

    RCGF 120cc Twin Cylinder Gas Engine

    Even with the trouble I had with this engine, I still really liked it - the engine ran well before it quit, and the new engine ran even better. My best experience throughout this review was the excellent customer service I received after the trouble began. The factory in China and the US service center in Arizona were great, and really went the extra mile to make sure I was taken care of! No matter what engine brand you may look at purchasing, they all can have issues - it's the customer service that can really make or break 'the next purchase' you make! My positive customer service experience with the 120cc twin will most definitely be on my mind when I look at purchasing another gas engine!

    4029 E. Golden Acres Drive,
    Sierra Vista, AZ. 85650
    Email: rcgfsale@zjrcgf.com

    P.O. Box 815
    480 Bonner Rd
    Wauconda, IL 60084
    Phone: 800-848-9411


    Distributed through
    Bob's Hobby Center
    540 N Goldenrod Rd
    Orlando, FL 32807
    Phone: (407) 277-1248

    Distributed through
    AirBorne Models
    4749 - K Bennett Drive
    Livermore, CA 94551
    Phone: (925) 371-0922

    Distributed by:
    Frank Tiano Enterprises
    3607 Ventura Drive E.
    Lakeland, Florida 33811
    Phone: (863) 607-6611


    11215 Paine Street
    Poway, CA 92064
    Phone: 1-858-748-6948

    Comments on RCU Review: RCGF 120cc Twin Cylinder Gasoline Engine Part 2

    Posted by: jefflangton on 01/08/2016
    30:1 wasnt enough lube? A dle would've let you fly into winter
    Page: 1
    The comments, observations and conclusions made in this review are solely with respect to the particular item the editor reviewed and may not apply generally to similar products by the manufacturer. We cannot be responsible for any manufacturer defects in workmanship or other deficiencies in products like the one featured in the review.

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