RCGF 40cc Twin Cylinder Gasoline Engine – Part 1

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Introduction

“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! With twin cylinder engines ranging from 21cc to 120cc, they’re bound to have an engine to fill your need.”

This is a quote from one of my previous RCUniverse reviews, and my statement is still true today! They’ve added more engines to their lineup, and have an even wider selection from which to choose. There are now two US service centers, and each RCGF engine comes with a two-year warranty! This review will be focusing on Version 2 of the 40cc Twin Cylinder engine – Just when you think it can’t get any better, it does! Have I piqued your interest? Read on!!!

Specifications

Price:   $409.99 USD

Available At:   rcgfusa.com

Type : 2 cycle piston valve type gasoline engine for airplane

Piston displacement Cylinder: 40cc  (2.44 cu.in)

Bore x Stroke (mm): 1.26 in(32mm) x 1.02 in (26mm)

Carburetor : Genuine Walbro

Ignition : DC-CDI (Computer Controlled auto advance, electronic ignition system)
Power supply: 
4.8-8.4V

Maximum Output :4.6HP @8600 RPM

Requires: Gasoline, 2-cycle oil, ignition battery & propeller

Speed Range : 1500-8600 RPM

90% high octane unleaded Pre-mixed gasoline  – Recommend: 30:1

Lubrication Oil : 2 cycle engine oil (Synthetic Oil Recommended)

Suggested Propellers: 19×8, 19×10, 20×8, 20×10

Suggested Break-in Prop: 19×8

Spark plugs: RCGF 1/4-32 plugs

Weight :

Engine: 2.32 lb (1052g)

2 x Muffler: 4.45 oz (126 g)

Ignition Module: 5.1 oz (145 g)

Total: Weight: 2.92 lb (1323 g)

Ignition Battery Required: 4.8-8.4 NiCd or NiMH, 6.6V LiFe or 2S LiPo pack

First Look

RCGF has continued to improve every facet of their product, including even the box! With a nice printed logo and information on the outside, Even the box looks better! Inside, I found a well protected engine and components! Laying out the major parts, I noticed that there is quality in the way they make their engines!

One of the first things you’ll notice that make version 2 different is the change to a canted plug design, and a 1/4-32″ spark plug. The plugs are small! The ignition module is fitted with 1/4-32 plug caps, and accepts a wide Voltage input range.

The four-bolt propeller hub is nice, and will keep the prop securely attached to the engine. Like all of RCGF’s other engines I have reviewed, the hardware included with the 40cc Twin V2 is more than adequate and definitely usable. The offset mufflers are made from aluminum and look nice.

Though the throttle arm is a little short on the genuine Walbro carburetor, it can be set up pretty easily with a computerized transmitter. The choke is also quickly accessible for easy starting.

Each piston sports a single piston ring, and the exhaust manifold machining is very nice!  RCGF has also included several decals with their new engines – I love the skull wearing the bomber helmet! There’s an instruction manual included, but it has been updated – the updated version can be found Here.

Photo Shoot

Installation

I’ll be using my Great Planes Avistar 30cc Sport Trainer ARF for this engine review – it currently has an RCGF 35cc Rear Exhaust engine installed, so I’ll have to remove it.

The left lower mounting hole needed to be filled in order to mount the 40cc twin, so I epoxied a dowel in the hole. When the epoxy had cured, I cut and sanded the dowel flush to the firewall. The horizontal and vertical center lines on the firewall were also extended.

At this point in the installation, I was planning to cut and install a brand new cowl for the 40cc twin. In order to get the spacing correct, I used some aluminum stand-offs and a 10mm light ply plate. With the mounting holes transferred to the ply, I cut it to shape and marked the horizontal and vertical center lines. The arrow was added to mark which was was up on the ply plate.

Because I was using longer standoffs and the ply plate, I replaced the included hardware with 10-24 threaded rod, #10 washers, and 10-24 locking nuts. The threaded rod was cut to the approximate length, and inserted through the firewall.

 The ply plate and standoffs went on next, and the engine was temporarily placed on the threaded rods. With accurate rod lengths attained, I cut the threaded rods to the correct length.

I marked and drilled a new throttle pushrod hole, tested the pushrod configuration, and then removed the engine. Excess material was removed from middle of the ply plate to reduce weight.

I reinstalled the engine and throttle pushrod, and then installed the mufflers. The rear exhaust manifold bolt is installed through the exit pipe of the muffler. A drop of  Pacer Z-42 blue thread locking compound is all I use on the exhaust bolts. The 1/4-32 spark plugs were installed – these plugs are tiny!

Because of the 40cc Twin’s carburetor placement, I had to replace the fuel inlet tube from the fuel tank to the carburetor. Thanks to the Avistar 30cc Sport Trainer ARF’s large top hatch, access to the fuel tank was easy! The Ignition module was installed next to the fuel tank, with a piece of DuBro 1/4″ foam rubber between the module and plywood tank tray.

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The Falcon 19×10 Beechwood propeller was drilled and mounted on the engine. The aluminum spinner was included with the Great Planes Avistar 30cc sport trainer ARF! With that, the RCGF was ready for some runtime! Because I would have had to remove too much material to fit the cowling over the engine, I begrudgingly chose to leave the cowl off.

Ground Running and Tuning

Because of the unpredictability of the weather in Minnesota, I was unable to get the RCGF 40cc into the air before it got cold. I did have a warm, albeit windy afternoon to run the engine on the ground for a bit.

For the initial startup, I left the carburetor set as it came from the factory. I filled the Avistar’s fuel tank with 30:1 non-ethanol gas/oil mix and closed the choke on the carb. My trusty heavy duty starter make quick work of turning over the engine, as it ‘popped’ quickly. I opened the choke, and started it again. the engine came to life quickly, but was running on only one cylinder. Due to the fact that I have had trouble with these 1/4-32 spark plugs in the past, I started there with troubleshooting. I switched the spark plug wires from side to side, and the ‘dead’ cylinder stayed on the same side. Unfortunately, It started to rain on me, so I had to put the plane away for a few days – In the mean time, I ordered some 1/4-32 RCEXL spark plugs from my buddy Mike Williams at www.ibcinyourc.com. Mike is a great guy, and will do his best to get you what you need!

When the new spark plugs arrived, I installed them started the RCGF 40cc Twin again. This time, the engine came to life on BOTH cylinders, and ran beautifully! Take a look at the video below to see how well the engine ran on the ground.

More to Come…

Just to let you all know, I will be getting the RCGF 40cc Twin airborne just as soon as I can in 2018. I will say this – the engine, out of the box, looked great, and was easy to mount on the Avistar. It runs beautifully on the ground, and like all my other RCGF engines, I expect it will run perfectly in the air as well. I’ll get the flight review done ASAP!

And, as always, thanks for taking a look! -GB

Contact Information

RCGF Engines:   www.rcgfusa.com

Great Planes:  www.greatplanes.com

Pacer/Zap Adhesives:   www.franktiano.com

Falcon Propellers:   www.justmodelprops.com

DuBro:   www.dubro.com

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4 Comments

  1. The rcgf is a nice little engine. not bashing it. but as a reviewer you should suggest they provide a decent arm not a bandaid using epa.. i highly doubt any experienced gas modelers will use the carb arm as is so why not be honest about it.

  2. Geoff, nice write up. a couple things jump out that i would challenge as accurate. The “throttle” and “choke” arms on the carb appear to be the standard walboro arms made for a z bend connector for a gas powered tool.. weedeater, chainsaw, etc.. they are generally too short to get reasonable resolution without severely limiting the servo throw. Since the last 25-30% of the carb travel has very little effect on the rpm, this short length amplifies the issue. The cut the throw with a computer radio is bad setup. Tell it like it is. or wt least should be.. it RCGF wants to go the extra mile they up and provide a decent arm, the end user should expect to spring 10 bucks for an aftermarket arm, or live with an much less than optimal linkage geometry with a bandaid in the end point adjustment..

    • 2Walla – I appreciate your opinion, but beg to differ. I see no reason to alarm people, or bash RCGF by saying that the throttle arm is too short. I’d much rather offer a positive solution to the issue. As most pilots have radio systems that have End Point Adjustment (EPA), it is well within the capability of most modelers to set up a smoothly operating carburetor. It’s no different than if you were to limit the travel on an aileron or flap to avoid over extension of said control surface. I always set up my throttle mechanically first, which includes full open to close travel of the carburetor, then fine-tune with EPA from there.

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