RCGF 70cc Twin Cylinder Gasoline engine

0

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 the new 70cc Twin Cylinder engine, and I can’t wait to show you what’s in the box! Have I piqued your interest? Read on!!!

Specifications

Price:   $499.99 USD

Type : 2 cycle piston valve type gasoline engine for airplane

Piston displacement Cylinder (cc) : 70cc(4.27 cu.in)

Bore x Stroke (mm): 1.53 in(39mm) x 1.18 in (30mm)

Carburetor : Genuine Walbro

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

Maximum Output :7.4HP

Requires: Gasoline, 2-cycle oil, ignition battery & propeller
Speed Range :
 1500-8600rpm

90% high octane unleaded Pre-mixed gasoline  – Recommend: 30:1
Lubrication Oil : 2 cycle engine oil (Synthetic Oil Recommended)

Suggested Propellers: 22×10, 23×8, 23×10,24X8

Suggested Break-in Prop: 23X10

Spark plugs: NGK CM6 Type

Weight :

Engine: 3.32 lb (1508g)

2XMuffler: 5.36 oz (152 g)

Ignition Module: 5.11 oz (145 g)

Total: Weight: 3.98 lb (1805 g)

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

First Look

RCGF is really stepping up their game – the plain boxes have been replaced by a nice printed box! Inside, I found the engine parts all wrapped in foam and bagged. I really like the way this engine looks, and it smelled like gas when I pulled it out of the box – I’m guessing it was test-run at the factory!

The mufflers, and all the hardware are first rate, and look very nice – No cheap hardware here!

The electronic ignition system is pretty standard these days, and can handle any power source from 4.8 to 8.4 Volts!

A genuine Walbro Carburetor is included, and the reed block aligns the carburetor for straight-shot pushrod alignment.

The casting on all parts was very well done – I found no areas of pitting. All mating surfaces are machined for a good tolerance-fit as well. The pistons are of single-ring design, and the spark plugs are canted to keep the over-all width to a bare minimum. Nice work, RCGF!

Pre-installation Photo Shoot

Engine Installation

Since my World Models 29% CAP 232 (Available through Airborne Models in the US) had an engine already installed, the first thing I had to do was remove it. The DLE 55 was a beast, and hauled the CAP 232 around effortlessly, so the 70cc twin will have stiff competition. With the old engine out of the way, the firewall was ready to accept the 70cc twin!

As luck would have it, the RCGF 70cc twin used the same mounting holes as the DLE 55 did, and the included stand-offs put the propeller hub at the same distance from the firewall – talk about a drop-in upgrade! I added a large ‘fender’ washer to both sides of the firewall to prevent any crushing of the wood – this made the included mounting screws a little on the short side. Thankfully, I had some 5x50mm machine screws on hand to replace the included screws.

The fuel line was not quite long enough to reach the new carburetor location, so I had to add a short section of Tygon Fuel line. I always keep a good supply of Tygon on hand, but if you need some, it’s available from DuBro RC Accessories. The  line I’m using here is the Large (1/8″ ID) Tygon Gas tubing, and Dubro sells it in 3′ sections or on a spool of 30′.

The hole in the throttle arm was too small for a DuBro 2-56 Swivel Ball Link, so I opened the hole with a 3/32″ drill bit. This made attaching the swivel ball link easy. I also relocated the throttle servo due to the different placement of the carburetor on the 70cc Twin. Thanks to the endpoint adjustments available in my Hitec Flash 7 transmitter, I was able to make the linkage work at the odd angles.

The ignition module was attached to the motor box with zip ties and a small piece of DuBro 1/4″ Protective Foam Rubber to insulate it from vibrations. I attached the two mufflers using the included hardware and a few drops of ZAP Z-42 Blue Thread Locker , and snapped the spark plug wires to the spark plugs.

Lastly, I installed the Falcon 24×8 Beechwood Propeller and a polished aluminum spinner. I did find that the included propeller bolts were too short to use both the Falcon prop and the thick backplate of the spinner, so they were replaced with 5x40mm socket-head machine screws. For the purposes of this review, I’m leaving the CAP’s cowl off, but it was wide enough to conceal all but the very tops of the spark plug caps. With the prop and spinner installed, I charged the flight and ignition batteries (for this review, I’m using a 4.8 Volt NiMh battery for the ignition) and got the 29% CAP 232 ready to fly!

Photo Shoot

Flight Report

I didn’t have to wait long to get a good day to fly the World Models 29% CAP 232 with its engine upgrade, but I did run it at home for about 20 minutes before taking it to the field. It’s always easier to get a gas engine running the first time without a crowd of on-lookers… With ignition turned off, I closed the choke and flipped the propeller over a dozen times or so – this drew fuel from the tank to the carburetor. I then turned on the ignition, left the choke closed, and flipped the engine about six or seven times before I heard the first ‘pop’ from the engine trying to run. I opened the choke and flipped the propeller a few more times, and the engine came to life!

Now, per the manual I received with the 70cc twin, it says to break-in the engine at a rich needle setting on the ground for 20 minutes at 2,500 RPM, so this is the procedure I followed. RCGF’s online manual has been re-written, and includes no mention of breaking in the engine at all, stating only to set the needles for optimum power using a tachometer. I am awaiting clarification from RCGF on which method they prefer for their engines. Nevertheless, a short break-in on the ground has never HURT any of my gas engines, so I’ll continue to do so until I hear otherwise.

Fast-forwarding a couple of days, I met my good friend and video pilot, Jim Buzzeo, at the WARC (Willmar Area Radio Contollers) flying field to put the upgraded CAP 232 to the test. For this test, I will be using my standard fuel 30:1 mixture, which is 91 Octane non-ethanol gasoline and FVP synthetic 2-stroke oil. I run this 30:1 mix in all of my RCGF engines and it works very well!

The fuel tank has now been filled, and I powered up my transmitter, receiver, and ignition. I closed the choke on the engine and flipped the prop. Even after sitting for a few days, the carburetor had not lost its prime – the engine popped after about four flips! When the propeller had stopped moving, I opened the choke, flipped the prop about five or six more times, and the 70cc twin came to life once again! As I always do, I let the engine get up to operating temperature by pushing the throttle stick forward about two clicks while holding on to the tail of the plane. Within a minute or so, the engine was purring nicely and ready to go!

Out on the field, the CAP 232 was pointed into the breeze and the throttle was opened slowly – the plane was airborne by the time the throttle was just above half – stick! Climbing out easily, the throttle stayed just above half – this proved to be plenty of power to pull the CAP 232 around with ease! For the next few minutes, Jim put the CAP and 70cc twin through its paces – the engine never bogged or missed, and ran flawlessly!

The CAP was nowhere near running out of fuel when we decided to bring the plane in for a landing, but we had another plane and engine to test on this nice Saturday afternoon. Jim lined the 232 up into the wind, pulled the throttle back to nearly idle, and let plane settle in gently. The engine ran perfectly from start to finish!

Check out the video I put together of the RCGF 70cc Twin’s first flight!

Summary

I really like the new 70cc twin cylinder engine for RCGF. It was a drop-in replacement for the DLE55, and provided a definite upgrade in performance as well! The fit and finish were both great, and installation couldn’t have been easier! I’m really liking this engine, but ran into one small problem after the initial run – one ‘side’ of the ignition module quit sparking, but a quick email to the manufacturer had a new module en-route quickly! Now THAT’S service! -GB

Contact Information

-RCGF-

www.rcgfusa.com

-Airborne Models-

www.airborne-models.com

-Hitec-

www.hitecrcd.com

-DuBro-

www.dubro.com

Share.

About Author

Leave A Reply