Build By Eric CA.

GFZ - Gasser conversion kit for TZ90V2/FRENZY 90 Belt or TT drive


The TZ90V2 kits & replacement parts now available from 

What you will find in your GFZ Kit 

  1. Pair (2) front engine mount frame sections in 2.3mm thick G10/FR4 with cover plates.
  2. Pair (2) rear engine mount frame sections in 2.3mm thick G10/FR4 for belt conversion.
  3. Pair (2) rear engine mount frame sections in 2.3mm thick G10/FR4 for TT conversion.
  4. Under carriage battery or electronics mount in 2.3mm thick G10/FR4.
  5. Engine heat deflector in 2.3mm thick G10/FR4
  6. Throttle servo mount in 2.3mm thick G10/FR4
  7. Throttle servo mount spacer in 6.5mm thick G10/FR4
  8. Top engine mount in 6.5mm thick G10/FR4
  9. Bottom engine mount/plate in 6.5mm thick G10/FR4
  10. 4 off M5*16mm grade 12.9 countersunk bolts/screw (Top Engine mount)
  11. 4 off M5*25mm grade 12.9 socket cap bolts/screw (Engine base plate)
  12. 1 off M6*12mm 8.8 grade bolt with 12mm flat washer  & spring washer (engine shaft)
  13. 2 off M4*10mm grade 12.9 socket cap bolts/screw (clutch to clutch housing)
  14. 8 components M3*16mm grade 12.9 socket cap head bolts/screw
  15. 6 components M3*25mm grade 12.9 grade or stainless socket head bolts/screw (base plate to landing strut fitting)
  16. 8 components M3*10mm o.d. washers (landing strut face)
  17. 14 components of M3 locknuts zink plated
  18. Cnc aluminium clutch shaft engine adaptor
  19. Cnc aluminium starter shaft holder
  20. Two 10id*19od*5mm thick bearings (6800ZZ)
  21. One  5id*11od*5mm thick bearing (685ZZ)  

Additional items required

  1. Gas fuel tank that is within the parameters of 85mm wide * 75mm high * 150mm long or a Trex 700N fuel tank.
  2. Any generic tank guard material or make your own by slitting black fuel line along one side.
  3. Part TZ1619 frame spacers (8 supplied in pack, 1 pack required).
  4. Part TZ1629 landing strut bracket (4 supplied in pack, 2 packs required)
  5. Trex 700N clutch assembly (14 tooth M1 pinion, clutch bell & starter shaft)
  6. Lynx LX0135 RevB gas clutch

Design evolution

This conversion project has been through various phases over the past three years before being completely satisfied with its current release revision.

1) Complete new frame redesign & manufacture with original clutch & tank.
2) Offset frame design much like a Trex450v2.
3) Its current form with Lynx LX0135 RevB clutch, one kit for both Belt drive & TT versions.
4) Brute performance version.

Offset frames or frames with spacers have more flex than a solid frame or laminated frame connection. If say servos or fuel tank where on a separate offset frame, this would be a good move, but not between engine & gearing. This concept was scrapped due to frame flex.

The GFZ kit is a true conversion within every sense of the word. It respects the original host & utilises many of the original components including the frames. There is a little more work in preparation than the Brute kit (four cuts on the original frame & a few holes to drill out) but well within the capabilities of anyone attempting to become involved with a large scale gasser.
Design features generous air gap between the engine & surrounding components, reducing heat & harmonic vibration transmition.
The base & top engine mounts are 6.5mm thick G10/FR4 & mounted much like the original nitro engine along the x & y axis directly under the main shaft. To offset flex & any resonance both mounting plates required thicker material. Prior, mounting was also attached directly to the frame beneath the servo's using thinner G10 base plate material; this in my testing induced more vibration along a path to the more sensitive components i.e. the electronics. The electronics tray position now experiences less vibration however a new position was designed beneath the fuel tank. This new position is in between four mounting bolts away from the cylinder head & mounted on offsets. Testing shows that this area experiences less vibration than the electronics tray. Any weight gained by the thicker engine mounting plates is offset by the benefit gained.


The fuel tank bay is designed to take any gasser specific tank within the parameters 85mm wide * 75mm high * 150mm long, or even Trex 700N Tank mounted in a reverse position (better option if not using the standard can muffler).

If you decide at any time the GFZ can be updated to the Brute with only the 2.5mm frame components.

Setting the myth straight the original TZ90 clutch with the original liner changed in my testing out preformed the original Trex 700 clutch. An earlier version of our Trex 600n conversion actually utilised the frenzy clutch over the Trex 700 clutch (pre Lynx gasser clutch). One of the main problems of gasser conversions is clutch slippage under the combination of 3D flight loadings combined with the extra torque loadings of a gasser engine at lower rpm settings.

For this type of use the Lynx LX0135 RevB design is of the most benefit as there is more mass in the clutch shoe without the additional weight penalty of an RC marine or RC car clutch system. 


Additional assembly Tools required

The Frenzy assembly manual is available under the dowload tab in PDF format.

  1. Dremel tool with abrasive cutting wheel or a fine metal hand blade saw.    
  2. M3 & M4 drill bits.
  3. Fine grade sanding paper or wet & dry.

Front section of frame preparation

  1. Basically take the right hand side frame & follow the throttle servo access hole vertically & horizontally as shown (1) scribing a line using a metal rule & blade (yellow dashed line).
  2. For the belt conversion drill out to enlarge the existing M3 four holes position (2) using a 4mm drill bit. DO NOT DRILL OUT THESE HOLES FOR THE TT CONVERSION.
  3. Overlay the new Front frame section into position, square up & tighten the two sections together using temporary M3 bolts & locknuts inserted at position (3). Now drill out new hole at position (4) using a 3mm drill bit & the new frame as guide. Now remove bolts & frame section.
  4. (5) Front sub frames in kits will now have two sets of hole positions for mounting front frames to part TZ1820.The upper set of holes are to be used for the TT conversion & lower hole position for the belt conversion.
Rear section of frame preparation
  1. Overlay new rear frame section & insert 4 temporary M3 bolts as shown at position (6) then slightly tighten with lock nuts. Scribe along side of the new frame for cutting position (7), shown with yellow tape for visibility. The new frame sections will be flush with the base of frame on the belt version & protrude 0.5mm past the base of frame on the TT conversion.
  2. Now drill out the two holes at position (8) with a 3mm drill bit. Remove bolts & rear frame section & mark down a horizontal line (9) 32mm for belt & 37mm for TT conversions (dashed yellow line), from main shaft bearing block position.
  3. Cut marked front & rear frame positions using a dremel tool with a thin abrasive cutting wheel. This produces excellent results. Wear eye & respiration protection. Alternatively cut by hand using a fine tooth metal saw blade. Sand cut edges with fine grade sand paper or wet & dry.
  4. For the TT conversion drill out both holes at position (10) with 4mm drill bit. DO NOT DRILL OUT FOR BELT CONVERSION.
  5. Clutch mount slot position (11) will need to be elongated with a needle file by approximately 2mm towards the nose of the heli.

Now use the cut frame as a template for the opposite frame.

U-Beam cross member preparation (this step is optional)


Once the frame has been prepared the middle brace of the front aluminium U-Beam cross member TZ1622 can be cut away for sparkplug access then filed, sanded & painted as shown in the photograph above. Cutting can be achieved with a simple hack saw (fine tooth metal saw blade) & holding the piece in a vice.

Tip: use scrap timber, plastic or G10 off cuts within the jaw vice or clamp while holding down to avoid marking the cross member. 

The Front frame replacement sections have been designed solid with no voids for additional strength, & there is a three ply lamination at this point for this modification. You can choose to leave TZ1622 as is. The only inconvenience is that the base plate & motor will need to be removed for sparkplug access. 

Frame assembly

Now assemble entire model as per manual using the new front & rear frame sections. Where the frames overlap longer 10mm M3 bolts have been provided for use instead of the standard 8mm bolts.


Above photos show rear frame assembly & position of;                                            


  • TZ1619 frame spacers
  • Two new landing strut adaptors TZ1629
  • Two spacer washers cut from M3 scrap frame section or two 1mm thick washers per side.
  • Replacement of rubber grommets previously removed.

With the TT version make sure the rear most brackets (TZ1629) at position (10) are flush & level with the forward brackets, achieved by tightening on a flat level surface.


Above photos show front frame assembly & location of;
  • TZ1619 frame spacers.
  • Landing strut adaptors TZ1629
  • Modified U-Beam cross member TZ1622                
  • Throttle servo mount & throttle servo spacer on side frame.

The right hand side (throttle side) canopy spacer/mount will need to be modified. Mark half way along the thicker threaded section of spacer as shown on both sides. Mount in a vice & cut down with a fine tooth metal saw blade or dremel tool. File or sand to clean face, clear burrs & thread a spare M3 bolt/screw to clean & clear the threads. Don’t use the canopy screw to clear the thread as it may become damaged due to burrs.


Engine Mount Assembly

Rotate the pull start assembly on the engine so that the pull chord handle is located towards the carb side.
Remove the four bolts of the fan shroud housing, place the bottom plate/engine mount over & tighten the plate to engine with the 4 M3*25mm socket cap head bolts supplied reusing the washers & applying thread locker. Bolts shown in photo are in stainless to differentiate from black back ground. Bolts supplied in kits will be black high tensile steel. New bottom plate will not have notch cut out for exhaust if using the stock can muffler large x-port spacer is recommended.

On most engines the M5 washer 5mmID*10mmOD*1mm will need to be installed as shown in the above photograph positioned between the metal housing & new G10 plate (location below the carburettor). This is because this section is 1mm thinner than the other 3 sections, measure the thickness of the black fan shroud at all four mounting locations for confirmation.

The optional battery/electronics mount shown installed above left reuses the tank mounts/offsets & bolts. This under carriage mounting plate can be used as an optional battery mounting position to adjust CG (nose pitching to far forward) or as an optional electronics mounting position such as auto pilot sensors.

Place the top engine mounting plate over the engine shaft in the position shown with the narrow part facing away from the cylinder head & towards the tail (above right). The countersunk screw section of the plate must be installed facing up.
Tighten the plate to the engine using the 4 M5*20mm countersunk bolts/screws supplied with thread locker (stainless depicted 12.9 supplied). Install the two new landing strut adaptors TZ1629 as show with the flat face outwards. Use the supplied M3*16mm socket head bolts/screws & locknuts for this step.
Install the heat deflector plate, you may find it easier to loosen the two shroud screws on the opposite side. Exhaust spacer in conjunction with the heat deflector is a solution to reduce heat to electronics & accredited to Roto terrier.

The exhaust spacer shown is the large X port, if using the RGX muffler I would still recommend using a thinner exhaust spacer to allow at least 25mm clearance between the fuel tank & exhaust, if you don't you will notice  tank deformation over time due to heat. The better alternative would be a muffler with a central exhaust mount such as the torpedo V5.

Now install the clutch adaptor onto the engine shaft. Inspect the edge of the engine shaft for burrs or irregularities & gently file or sand smooth if found. Remove your spark plug & install engine stopper tool or place a few inches of non fraying chord through the spark plug hole making sure that the piston stroke is past exhaust & inlet positions, then tighten adaptor & remove tool or chord, then reinstall park plug.

Above photo shows the removal of clutch adaptor using two long m4 socket head bolts & a scrap piece of any flat thin plate/plastic. Tighten both bolts at equal rates. Install the Lynx LX0135 RevB gas clutch onto the clutch adaptor & tighten using thread locker.

A note on weight
Standard can muffler with large X port spacer & exhaust deflector weighs 243 grams

RJX muffler = 346 grams
HPI foam filter = 59.2 grams
& standard air filter 40 grams.
Typical filter with Velocity stack = 115.5 grams
Total 159.3 - 178.5 grams in weight saving on these two items.


Clutch bell parts & assembly

1. Parts for this stage; Trex 700n clutch bell ,14 tooth M1 pinion & starter shaft. TZ clutch holder with supplied bearings installed. New starter shaft bearing holder with supplied bearing installed.

2. Screw with thread locker the 700n clutch bell to the pinion do not over tighten. The direction of the thread is self tightening.

3. Slide the TZ clutch holder with the new bearings installed onto the pinion.  IMPORTANT: the top & bottom bearings of the original TZ clutch holder needs to be changed with two 10 ID * 19 OD * 5mm bearings that are supplied. You will notice that there is a bearing that sits deeper in the holder (7mm depth side) and another that sits more flush with the housing (6mm depth side of housing). The housing is installed with the deeper or 7mm side of the housing facing up towards the rotor & the 6mm side facing down towards the clutch.

4. Now slide starter shaft into position.

Note: The Pinion as well as the original Align Pinion is designed as a sliding fit for ease of assembly. Pinion shaft & internal bearing ring is then to be adhesive fixed. This is usually done with mild-mid strength thread locker, obviously don’t get it all over the bearing.  Use high strength thread locker on the pinion retainer nut. The pinion, internal bearing rings & retainer nut should all then all rotate at the same rpm as one unit. If thread locker/bearing retainer is omitted in the assembly, this is when you will notice a groove on the pinion shaft & wear of the retainer nut due to the internal bearing ring being free to rotate on the pinion shaft at a slower rpm. 


5. Install the supplied bearing 5ID* 11oOD * 5mm into starter shaft bearing holder as shown, then screw on the new starter shaft bearing holder in place with high strength thread locker, do not over tighten & allow 24hrs to cure. It is also good practice to allow a thin shimming washer between the bearing & holder. If either an adequate amount of high strength locktight is not used or the locktight is not allowed to fully cure thread damage may result over a long period of time.

6. Install & tighten the trex hex starter coupling.

Please note: Align has changed the thickness of the clutch liner & it will now need to be sanded down evenly to approximately 1.15mm in thickness or untill there is a snug & not to loose fit of the lynx clutch against the liner.

Now slide entire stack into position & lightly tighten.
Now you are ready to install engine with mounts into position. Angle slightly into position, align with starter shaft & slide up into position. Install fixing lock nuts & bolts to positions other than those of landing struts & snug tighten so engine is still free to slide, find appropriate meshing of pinion & main gears, and then tighten mount bolts. Finish assembling landing gear, the supplied m3 washers face
Part TZ1629 landing strut bracket on the slit. In all there are 10 engine mounting bolts.

There should be ample clearance between the Trex 700 clutch bell & TZ1820 frame brace. If during fitting you see the need for a little more clearance it can easily be achieved by removing & sanding a little with metal abrasive paper or dremel tool.

Take the front landing gear strut & draw a line connecting the outer edge of slots as shown (not centre line). Measure centre along this line then mark two drilling points 10mm either side of centre point as shown & drill two new M4 holes at those two positions (do not drill centre mark). Loosen front mounting bolts, & install landing front landing strut as shown & then rear & skids.


Trim & cut out the canopy as normal. Now use the top of the window cut out to mark a curve on the bottom of the canopy. Flip the canopy over & mark a centre line on both pieces shown in red marker, then align the top of the window cut out where it meets the change in bottom curve as shown. Mark this curve & cut out. This cut out section at the bottom of the canopy not only allows clearance of the landing strut but aids in airflow & electronics cooling during forward & reverse flight from the extra heat generated by these larger bore engines.

Fuel Tank

Install fuel tank & plumbing. Pictured above is a 750cc gas fuel tank (right) & a Trex 700N fuel tank (left) & mounted in the reverse position as the rear frame section has been designed for this contour. Install tank guard material & strap tank in tight with two large 450mm cable ties. The black fuel tube & felt clunk that comes with your engine is ideal to use as the internal tank fuel pickup line. Make sure there is enough length so that the clunk reaches all positions of the tank, flip the tank upside down & also check. I like to keep tank plumbing as basic as possible & fill via the return line & drain via the filtered clunk pickup line. The vent is treated with a coiled fuel line & there are no “T”s, valves or unnecessary new holes in the tank. I also use filters on my filling station.



Credit goes towards this build for his detailed mounting of the Trex 700 tank using Maverick tank frames shown below. A tailored GFZ Trex700 tank holder plan utilizing existing mounting holes & tank suspension in pdf & dxf files is avilable in the download section for those that wish to cut there own by hand or 3D print. If you are tracing or spray gluing the pdf file onto material make sure once printed it is to scale by measuring the 140mm scale reference line. I had to bump my printer up to 102% to be exact. If using plastic board test an offcut  with gasoline before cutting.
quote "In the picture you will see that I used stock fuel tank standoffs on the right side I used two full size and on the left I cut one in half. 3 mm bolts with lock nuts.On the frame I split fuel tubing and silicone in place.Very solid. The frenzy has the narrowest frame I've seen and I was worried about mounting the tank knowing that I am going to put the heli into a fuselage later."

Tony (US)

This builder from Australia (Bob from WolfModels) has developed CNC landing skids for the TZ90 that are also avilable for all to purchase. He also has an extensive stock of replacement parts & TZ90 kits. Click on the photo for the link.

This builder (below) from UK mounted a 1000cc tank & at 1600 headspeed achieved 1 hour flight time.. quote " This is an insane combo I used to get tired coming in to change battery
packs, never ever thought Id say Im getting tired being in the air, Im hooked"

Richard (UK)

Trex 700 Metal Tail Rotor Holder part No. H70T001XX. This is a full metal hub & tail blade grip update that fits the Frenzy 6mm shaft with no modification work, bolts straight on. Good mod to replace plastic Frenzy grips. I also mounted Trex 700 Landing struts & skids as you have shown on the Maverick Build page, not only does it look better in my opinion but the Trex struts are less brittle and less prone to breakage.

Peter (US)

I bought some plastic aileron control levers for a JR vibe 90/50 as in crash mine broke. Almost identical to the TZ ones except they take two 3x7x3 bearings each (available from eBay/hk for peanuts) and the TZ ones use 3x8x3 bearings. Anyway the JR part number is: JR-96146 you will also need four 3x7x3 bearings and they will bolt straight up. 

Justin (AU)

Where the plastic tail drive gear mounts to the main shaft, instead of using the two M3 grub srews supplied, drill right through the main shaft with an M3 drill bit & fix gear with high strength M3 12.9 cap head bolt & lock nut. In the event of a tail tap the sheared grub screws will cause difficulty to remove tail gear & bolts. The TT version now has this modification standard.

Loz (AU)

If you want to replace the plastic tail blade holders on the Frenzy, the HK600GT tail rotor holders will fit straight on the Frenzy hub. You will need to shim to get a nice tight fit utilizing the existing shims within the frenzy tail hub setup. My HK600GT tail blade holders came with only radial bearings, I had to replace outer radial bearings with spare thrust bearings I had.
If using the Trex 550/600 tail rotor holders the attachment arm to control link will need to be filled down a little. With the HK tail rotor holder the attachment arm to control link is actually a separate spacer but does not come with the unit. Use or modify spare M2 bushings or offsets. The best part of this mod is not only the price but it works better than the Frenzy plastic tail blade holders.

Duncan (NZ)