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Apr 26, 2015, 09:15 PM
Chris Reibert
crmodels's Avatar
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Goblin 630 Competition to Gas Goblin conversion

Build Thread - Leviathan Goblin 630 Gas Conversion

Well after 28yrs in the hobby and never owning a gasser plane, Heli, car or boat o finally made the juno into the unknown. I called up Carey Shirley at Gas Powered Helicopters and told him I had a Goblin 630 I wanted to convert to a Gasser. No more than a few hours later he had a full parts list and invoice of everything I needed. What's different about this build then the hundreds of others I've built is that I am going into this project completely green. I think it should be a fairly decent easy build for a gasser novice and with Carey and Tom an email or text away I think I will enjoy this very much!

My donor 630 ready for an overhaul


Everything from Carey at Gas Powered Helicopters came well packaged and each part needed to convert your Goblin comes in its own brightly labeled bag. Having met Carey twice now down at OHB I even bought some apparel and stickers to support him at my local flying field.

All the goodies I ordered from Carey at Gas Powered Thoughts

Conversion kit

What I purchased to complete the conversion
- Leviathan Goblin 630 Conversion kit
- Fuel tank and plumbing kit
- Top start kit
- TRM VX300 Special Edition engine
- RJX pipe
- Clutch kit
- MKS HBL980 HV throttle servo
- Pulse 2s 2250mAh lipo
- Custom red air filter
- Scorpion backup guard
- WR lipo battery monitor
- EC3 battery cable extension
- EC3 to Y-harness RX connector

I ran out to the field for one last electric flight on my Goblin 630 and when I got back home I broke it down to give all the donor parts to the Leviathan build. After watching Carey's Goblin 700 conversion build videos countless times and reading his build thread at least three times I laid out all my parts on the table and began my journey into the world of gassers.

My Goblin 630 all broken down ready for its gasser makeover


I purchased the 14oz fuel tank kit that Carey recommended instead of trying to gather all of the right parts and supplies at my local hobby shop.

The fuel tank kit included:
- 14oz Du-Bro fuel tank
- Felt clunk rated for gas
- Custom made fuel inlets and vent fittings
- T-fitting and hardware
- 24" of Tygon fuel tube
- 18" of fuel proof vent tubing
- 6" of flexible fuel clunk line
- Gas proof tank end plug

I assembled the fuel pickup clunk line and drilled all of the 3/16" holes to fit my vent and filler fittings. Make sure to remove any plastic shavings before you install the fittings and end plug onto the tank. If you don't buy the fuel tank kit from Gas Powered Helicopters make sure the clunk and fuel stopper you decide to use are rated for gas. For not building a gas tank since the late 1990s it went together very easy in about 15 minutes.


For my build I chose to go FAST N LOUD and purchased the TRM VX300 Special Edition motor with RJX pipe. The fan shroud cover and carburetor isolator are anodized a dark red on the Special Edition Gas Powered Helicopters motor and will match my iKON Edition Goblin perfect! Here are all the parts that I purchased to complete the motor assembly.

- Clutch kit
- Top start kit
- Custom red air filter

Parts to complete engine

The engine assembly only took me about an hour to complete. You first must mount the engine mount plate to the engine using the supplied M5 bolts. I used red loctite on any permanent engine parts I don't want coming loose over time. Next you install the clutch mount plate, washers, clutch and starter yoke if you plan to top start the model. Remove the Phillips screw holding on the engine shroud and install the Hostile R/C air deflector. This is used to direct the hot engine heat out of the frame and canopy. If you choose to use a new TRM motor the carburetor throttle arm is on backwards and you will need remove it to install a swash ball so you can operate the throttle via a throttle servo. Use caution when removing and installing the throttle arm so you don't damage the carburetor butterfly. Lastly I removed the pull starter and installed the fan cover as well as my custom red air filter. I will be going back and forth between top starting and pull starting to find out which I prefer. This concludes the engine assembly portion and man is it a work of art. I almost wanted to put the motor up on a shelf in my heli room and admire it.

Motor mount installed

Clutch mount and washers installed

Clutch and OWB starter yolk mounted

Throttle arm ball installed and arm repositioned

Hostel R/C air deflector installed

Engine build assembly complete with custom red air filter


The new main drive assembly will replace the stock motor mount and allow a place for our motor clutch to go. All the necessary parts for the drive assembly are included in the conversion except for the main drive belt supplied from your donor helicopter. It goes together fairly easy and everything mounts onto the clutch bell. Front bottom to top you install the bottom bearing block, washer, shims if needed to position the pulley, bottom pulley flange, pinion pulley, top pulley flange, top bearing block and finish it off with Loctite and the retaining nut. If you plan to run the top start kit install the two bearings in the top and bottom of the clutch bell. The start shaft than slides up inside from the bottom and the starter adapter cup installs onto the end of the shaft with Loctite and two grub screws. Before installing the side plates install the drive belt first and than Loctite the two grub screws. All of the side plate screws are the same size except the ones on each side of the rear top bearing block plate. These are shorter so they don't stick through the bearing block and destroy the belt. Before installing the drive assembly to the upper frame plate you must install the mounting studs, springs, washers and lock nuts from your donor model. Once you have giving time for the Loctite to set up slide the drive assembly up into the upper frame plate compressing the springs and slip the belt over the drive pulley. Next set the belt tension as it was on the original electric model and ensure the belt rides center on the pinion and pulley before tightening everything up with the lock nuts. If everything was done correctly, the rear of the main drive assembly should line up with the front of the upper frame plate.

Clutch drive parts

Inside parts installed and locked in

Main drive assembly complete

Main drive mounted to the upper frame plate


The main frame assembly starts by gathering a few small parts from the donor model. You will the frame spacers, washers, screws, and pinion guard. Before assembling the frame you will want to install the fuel tank isolator trim around the front inside of the frames and glue them in as this is what the fuel tank will sit against. The front frame doublers install onto the outside of the frames with a M8 button head bolt and a lock nut inside the frames. Use the supplied frame spacers and assemble and install the front battery tray and pinion guard. You will need your frame spacers and screws from your donor Goblin to complete the front of the frame. Before putting the two frame halves together sandwich the fuel tank inside the frame between the frame isolators and then Loctite and tighten all of the screws on the front frame posts.

Conversion frame parts

Fuel tank isolators installed

Battery tray and pinion guard trays

Installed into the frame

Fuel tank installed and frames united together

Next take your completed upper frame plate assembly and transmission into the frames by spreading the middle frames to allow the transmission and clutch bell housing to fit inside. Once snug into their place you can install the remaining M3x8 screws and frame washers as well as your canopy mounts using Loctite. I run RC Booya canopy mounts on all my helicopters for simplify when installing and removing my canopy between flights. Lastly slide the pinion guard into the back of the frame holes from your donor model.

I forgot to take pictures of these two parts together as I was excited to throw the motor in next... Here is a picture of what this completed step would have looked like.


I couldn't wait any longer so I installed a piece of Tygon fuel tubing to the filler line and eagerly pushed the motor up into the frame and clutch bell housing. I was amazed how well the motor fit and with the top start shaft sticking down inside the clutch bell housing there really was so aligning. I installed the the remaining motor mount screws and washers before installing the fuel line onto the carburetor and sat back to admire how well all of the colors jived. The special edition motor cover and custom air filter were a perfect match to my red MKS X8 servos! Now it was time to give her some legs to stand on.

The TRM VX300 SE installed

Starting to look like a gasser


The Leviathan conversion utilizes your existing Goblin skid supports and skids so remove them from your donor model. Lay the existing SAB skids onto the conversion skids and install the bottom skid bumpers with longer screws and connect the skids to the landing gear supports. Next you install the motor plate and two mount blocks to the skid supports using the existing holes in the skid supports with the four supplied M2 bolts and washers . I then removed the four M5 bolts out of the motor shroud and slid the plate onto the motor and re-installed the M5 bolts with Loctite. Once everything was installed and I checked clutch was center of the clutch bell I installed the four skid mount bolts she washers and tightened the four bolts on the bottom of the skids. I had to throw the RJX pipe on for a few upcoming build pictures.

Donor skids and conversion skids ready to be married together

Skids and motor plate mounted to the landing gear supports

Standing on her own two feet


The boom slides right into the new conversion frames as if they were stock and mount the same as before. Set the belt tension tight and tighten all of the boom screws and washers as well as the break away boom bolts. The throttle servo mounts from the inside of the frame and the servo horn aims down to achieve the best servo geometry.

Tail boom re-installed

MKS HBL980 HV servo


Time for the canopy to dress this build up. My canopy is for a Goblin 630 Competition so some dremel work had to be done to get it to fit onto the model. Make sure you leave room for the throttle servo horn linkage and air deflector. I got carried away and trimmed more than I needed to get it to fit but it still came out decent.

Canopy trimmed and installed

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Apr 26, 2015, 09:16 PM
Chris Reibert
crmodels's Avatar
Thread OP

I installed the plumbing on the gasser today. Ran my fuel fill lines under the tank to a "T" filler fitting and ran the vent line in a coil and sent it out down the bottom below the tank and out the skid.


This is my favorite part of any build because everything really starts to come alive now. The electronics are powered by a Pulse Ultra 2s 7.4v 2250mAh lipo direct powered into a EC3 extension and a EC3 RX Y-harness. For security because of motor vibrations I installed the Scorpion Backup Guard for added protection and can constantly monitor in flight voltage via the bright status LED light from the Western Robotics battery lipo monitor. All wires were zip tied and neatly secured to keep for a clean build. Just need to order my fuel and accessories and then setup the throttle so I can start breaking the motor in!

She's alive!

Scorpion Backup Guard

Western Robotics lipo battery monitor

Power distribution line ran back to a EC3 RX Y-harness

The Western Robotics lipo monitor is mounted below canopy so it is visual the entire time


It's been over ten years since I touched a nitro and I've never done gas build so I had mix feelings going into this build. I was on the fence about the G10 parts in the conversion kit but once I got them in my hands and felt how thick they were I knew they would go together well on my existing Goblin 630. All in all from start to finish I think I have around 6hrs into the conversion build. The diagrams and part numbers and sizes helped with what parts went where. I also watched Carey's build videos and read through his build thread numerous times. I am extremely excited to order all of my fuel and supplies so I can start breaking this baby in and getting her airborne! Big thank you to Carey Shurley and Tom Welch for answer any of my build and setup questions thus far. Look for more pictures and flying videos in the near future.

Apr 26, 2015, 09:19 PM
Chris Reibert
crmodels's Avatar
Thread OP
Goblin Gasser 630 light 3D flight (4 min 12 sec)

Hello gallon #3

Getting low

Apr 27, 2015, 06:08 AM
Chris Reibert
crmodels's Avatar
Thread OP
Take a close look at the Leviathan Gas Goblin Conversion.

Leviathan Design Gas Goblin 630 Conversion Overview (11 min 9 sec)
Apr 27, 2015, 07:34 AM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar

A very neat and professional conversion. I've got a 630 comp, iust the standard electric one. I'd be interested in a comparison on weight and what sort of RPM you can govern with the gas engine? The video looked like fairly low headspeed, maybe 1900RPM?

The electric version is quite a heavy bird.
Apr 27, 2015, 08:37 AM
Flying Pitcher's Avatar
Originally Posted by JetPlaneFlyer

A very neat and professional conversion.
Apr 27, 2015, 12:43 PM
Chris Reibert
crmodels's Avatar
Thread OP
Originally Posted by JetPlaneFlyer

A very neat and professional conversion. I've got a 630 comp, iust the standard electric one. I'd be interested in a comparison on weight and what sort of RPM you can govern with the gas engine? The video looked like fairly low headspeed, maybe 1900RPM?

The electric version is quite a heavy bird.
Thank you

Yes RPM was around 1700-1900 with out a Giv running V curves until the engine is fully broken in. As far as weight goes my electric with packs was 11.9lbs and my gasser with full tank just hits 13.0lbs. Not bad for a gasser. Can't really feel the difference in the sticks.
Apr 27, 2015, 12:56 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
interesting. My 630 comp with batteries is 4.9Kb (10.8lb) ready to fly. I'm not sure where the 1lb saving comes from, unless you were running bigger batteries than me (3850mAh in my case).

I find with mine that i need to run pretty high headspeed to get good 'pop', but your flying looked nice and smooth at that lower headspeed. Do you know what the gas engine will spin the blades at once run in?
Apr 27, 2015, 03:45 PM
Chris Reibert
crmodels's Avatar
Thread OP
My 630 was running MKS metal case servos and two 5000mAh Pulse packs. The added weight did not bother my big air 3D and I was able to get 6min 3D flights! I believe with my motor and gear ratio I believe she will top out around 2300 max?

I normally fly my big air 3D at 1950 anyways for longer flight times and collective management.
Apr 27, 2015, 11:44 PM
Grumpy old git.. Who me?
JetPlaneFlyer's Avatar
5000mAh packs would explain it!.. I'm surprised you could shoe-horn them in. FWIW I've got metal servos too.

I really admire your collective management, my weaker skills demand higher RPM even at the lighter weight. FWIW lighter weight does help with flight time because I'm still getting 6 minutes but that's just big air sport type flying, no 'proper' 3D.

I guess with the gas engine flight time will be excellent? At 2300 she should 'pop' nicely, I think that's the recommended maximum safe RPM anyway.
May 18, 2015, 11:29 AM
Heli nut " the wife said so "
holtneil's Avatar
HI Chris lovely job mate , I love the goblin for the sound they make , lost that now , but it is really nice , Great flying as always your 28 years plus flying shows , your now be able to trim the weeds for longer , would be interesting to see how much faster she is over the standard Goblin
Well Steve is this your next project just dont tell the wife
May 28, 2015, 07:46 PM
Chris Reibert
crmodels's Avatar
Thread OP
Gave the Gasser 630 a new look. My new Canomod "Red Eyes" canopy, boom and fin showed up today.

Jun 05, 2015, 08:36 AM
Chris Reibert
crmodels's Avatar
Thread OP
Starting to lean her out more. Still running V-curves I will switch to a gov soon!

Fun with my Goblin Gasser 630 (3 min 19 sec)
Jun 05, 2015, 08:40 AM
Chris Reibert
crmodels's Avatar
Thread OP
I'm loving the new color scheme!

Jun 07, 2015, 02:57 PM
Chris Reibert
crmodels's Avatar
Thread OP
Check my first flight of the day on my Goblin.

Goblin Gasser 630 Sunday Fun (6 min 56 sec)

Last edited by crmodels; Jun 07, 2015 at 06:55 PM.

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