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Engine Conversions and Conversion Kits.

Auto-Moto 4-stroke engines

Air Trikes (AT) 160 and 280 gearbox conversion kits:

From summer 2012, we use new conversion systems for our engine conversions. AT-160 gearbox was designed using our 12 year experience with engine conversion. It is intended for 4-stroke auto-moto engine conversions up to 165HP and using them with propeller for NOT SERTIFIED experimental light aircrafts, hovercrafts, airboats etc. It can be used for tractor and pusher layouts.

AT-280 is designed for engines up to 280HP, for example 6-cyl Subaru. Information will be available soon.

AT-160 for Suzuki and Subaru

The gearbox set consists of:
1) 2 halves aluminum body with helical gears and bearings in oil inside, and 2 shafts – drive spline shaft and driven propeller hollow shaft
2) Spline rubber damper adapter + 6 hole Mercedes damper (big or small)
3) Hardware
The gearbox conversion kits include bellhousings and crankshaft-dampener adapters (or flywheels machined together with dampener adapters) different for different engines. They can include other conversion parts, for example starters, modified oil pans etc.
Bellhousings and crank coupler are different for different (Suzuki, Subaru, BMW, Nissan, Honda etc.) You can see AT-160 sets for Suzuki-GEO and Subaru with 2 different size rubber dampers and adapters at the picture

Available gear ratio 2.0; 2.3; 2.5; 3.0 This gearbox is light and more compact than previous SPG models, with more strong gears and bearings, easier to assemble (because of the spline shaft) and do preflight checking. TBO is more than 1000 hours. It is recommended to check and possibly change bearings and rubber dampener after 1000 running hours.

Dimensions and weight data:

AT-160 Metric Imperial
Offset (dimension between crank and prop shafts) 83mm 3.25"
Gearbox length (no bellhousing) 155mm 6"
Engine-prop flange dimension* 240mm 9.5"
Propeller hub Rotax standard**
Gearbox+spline adapter weight 7.9kg 17.4Lb
Full conversion kit weight* 11.6kg 25.5LB
*For Suzuki-Geo G10 and G13 short bellhousing, different for different bellhousings-engines.

AT-280 Metric Imperial (soon)

**Adapters can be ordered for other shape of propellers
Conversion kit weight data provided for the complete bolt on kit consists of gearbox, damper, bellhousing and hardware. The data can vary slightly during the production and depends on the engine model.

We build and fly trikes with Geo-Suzuki engines converted using AT-160 gearbox kits.

Advantages of this conversion kit are its high TBO and reliability, simple maintenance. The engine block is not modified, stock water outlet with thermostat. This makes the engine very thermo stable. I heard a lot about overheating problem from people using conversions with modified water cooling system but have never had it even with my small radiator closed by BRS system. It is also its high efficiency. Mechanical part of the engine conversion is simple. AT-160 instruction with step-by-step conversion pictures HERE. Click and look - nothing difficult to convert your auto engine using our gearbox bolt-on conversion system. AT system installation is even easier because of the spline gearbox-damper connection. Seeing is believing!

All conversion parts for Suzuki like mufflers, motormounts with rubber silent blocks, engine control system, control gauges, ultralight alternators and starters, light aluminum pulleys, radiators etc. are also available with our GEO-Suzuki engine conversion brochure. Some words about our new "small" improvements. For example a set of 3 light (crank, waterpump and alternator) aluminum hard anodized pulleys is not only weight saving. Increased alternator pulley diameter makes alternator running slower. It allows to avoid alternator overwork (usually we fly higher RPM than drive cars) and win a little bit of HP. Our light alternator set (alternator, aluminum bracket + tighten plate) saves 2.5-5lb of weight comparatively with the stock alternators.

Air Trikes Ent, our clients and partners have made a lot of different engine conversions for the last 12 years. We can state - AT Geo-Suzuki is not just an "alternative" engine but well proven and efficient powerplant for experimental aircraft and oper air propeller driven craft. We provide not only conversion kits but also ready-to-install powerplants based on low-mileage stock or completely remanufactured and modified GEO-Suzuki engines + KOOLprops:

a) Carburetor G10 with vacuum/centrifugal advance distributor. No electronic control - about 60HP
b) Throttle-body injection (TBI) G10 with DENSO Electronic Control Module (ECM) - 62-65HP
C) G10 Turbo with MPI, resonance intake, turbocharger – up to 92HP (intercooler & knock sensor can be used)
d) G13BA 8 valves SONS naturally aspirated – up to 80HP
E) G13BB 16 valves SONS about 100 HP naturally aspirated
f) G13GTI 16 valves DONS 110+HP naturally aspirated
g) G16 16 valves SONS NA about 115HP
h) BMW R serie engines (look below)

We sell gearbox conversion kits for these engines + for Subaru EA, EJ, Honda Civic & FIT. We also can design and make mount plates for other auto conversions.

Our standard trike engine is Suzuki G13BB. Around 100HP, 220-230 kg (500lb) static thrust is normal for a stock unmodified G13BB with AT gearbox and KOOLprop. Short takeoff, up to 1300 FPM climbing, from 6 liters (1.5 gal) per hour minimal cruise consumption, up to 90MPH level speed. Pictures of G13BB engines converted with AT-160 gearbox and installed on our different trikes below. Click on them to see more details.

GEO-Suzuki engine conversion brochure

Information brochure about converting Geo-Suzuki G series engines for Homebuilt aircraft and other air propeller driven craft is available for your order. The price is 99CAD paid with PayPal to E-mail address. This price included 4% PayPal fees, print and Canada Post regular mail cost. Do not forget to include your mail address. We send only printed version, no CD, no download. If you want more information about it, to see Content or read Introduction/Conclusion - CLICK ON THIS LINK.

If you can't use PayPal and wish to send 95CAD by check, or have other questions about ordering this brochure, contact us. E-mail addresses and phone # at the bottom of the page.

Honda-Fit engine conversion

Honda Civic engines were converted and used for aircraft before. These engines are highest quality (as everything made by Honda), so we were waiting for a new, more compact and light but very powerful L-serie engines. These engines came to North America under the hood of subcompact Honda Fit in 2007. Now they are well known, not expensive and easy available with very affordable price.

L15A VTEC engine official data:
Displacement: 1,496 cc (91.3 cu in)
Bore x Stroke: 73.0 X 89.4 mm (2.87 X 3.52 in)
Compression Ratio: 10.4:1
Horsepower: 81 kW (110 PS; 109 hp) @ 5800 rpm, up to 117HP at 6600 RPM
Torque: 143 N·m (105 lb·ft) @ 4800 rpm

It is 16 valve SONS. This engine block is about 10kg (22lb) heavier than well known G13BB, but 1.5L instead of 1.3 and has about 20HP+ If we compare it with G13BB:
Positive moments - timing chain instead of belt, 4 stock sparkplug-on coils (one for each cylinder).
Negative moments - more complicated motormount, bulky intake, more complicated stock control system (VTEC, electronic throttle control).
This engine is able to give about 300kg (660LB) static thrust on a trike (pusher config) comparatively with 240-250kg from G13BB. The gearbox conversion kit has been designed and tested in 2011. It can be your choice if you build a propeller driven craft. Pictures below - L15A on a test stand, L15A with installed SPG-4 gearbox kit:

Quick 2011 year update.

After tests of BMW R conversion system based on SPG-2(3) 2.5RR gearbox, we received many questions if we can supply conversion systems with a centrifugal clutch and higher than 2.5 ratio. This system is ready now. It is made based on a new reinforced SPG-4 gearbox with 3.0 ratio and Italian design centrifugal clutch rated up to 130HP. Two independent sections of 3 segments, connected by two springs each other, make this clutch very reliable. Look at the pictures below. There are also 2 pictures showing SPG-3 gearbox installed up and down at R1100 engine.

A new bellhousing for Honda Fit 2009-2011 L15 1.5-liter 16-valve 4-cylinder SOHC i-VTEC engine is ready. Now you can use this lightest and most compact from Honda auto engines for your aircraft with SPG-3 (2.34 and 2.5 ratio) or SPG-4 (2.8; 3.0; 3.16 ratio) This engine has 117 hp @ 6600 rpm and 106 lb-ft @ 4800 rpm (from official Honda website). I also decided to place a picture with 3 different models of gearboxes. SPG-3 left, reinforced SPG-4 center and SPG-2 (not in production anymore). As you can see, SPG-3 is an improved version of SPG-2, and SPG-4 is their bigger and stronger "brother".

General information.

Interest in 4-stroke auto-moto engines converting for Light Sport and Ultralight aircraft is growing all over the world. Everyone knows that the most popular 2-stroke Rotax 503 and 582 are not certified aviation engines but variations of snowmobile engines with all 2-strokers' problems. Prices of certified 4-stroke aviation engines are quite high. The active development of aviation piston engines has stopped more than 50 years ago with the jet age beginning. The same time, cars become more and more perfect. Modern auto engines are light, have high reliability and life time. Electronic ignition and fuel injection with microprocessor control system, low gas consumption and flight hour value, simple and inexpensive maintenance with attractive unit price, these features usually distinguish converted auto engine from its "real aviation" brother.

G10 Subaru + belt drive

I started to use 2-stroke, then 4-stroke Auto-Moto engines for aircraft in early 90-th. There is a lot of experience in converting of Subaru, Honda, Chevy, Nissan, Kawasaki and other engines but light and small GEO-Suzuki G10 AND G13 are the most interesting engines for me as Ultralight trike builder and pilot. G10 with stock fuel injection has about the same HP as popular Rotax 582 model. Trike with G10 has very good flight performances with significantly lower flight hour cost. Its TBO is about 1000 hours. Its alternator and starter + light battery allow you to start easy at any weather, have headlights, radio, intercom etc. Electronic control module with sensors easy fit it to different temperature, altitude, humidity, gas quality and let you know about possible problems with signal light. You don't need to spend a lot of your time for its converting. G10 Turbo, G13BA and G13BB have about the same power as Rotax 912 and 912S. Trikes with GEO engines operate for crop spraying in East Europe. Pilots fly over fields and trees with 10-20 feet altitude with 30 gallon chemical tanks for several hours a day. Heavy conditions demand reliable engines. That is why they use GEO-Suzuki.

Suzuki Power Group (SPG)-3 and 4 gearbox conversion kits:

These gearboxes were designed in 2008 as modifications of very popular SPG-2 system (was in production 2000-2008) for aviation conversion of 2 and 4-stroke engines. SPG-3 has the same gear pair as SPG-2 but lighter and easier to install-remove because of studs on the crank coupler used instead of bolts. Recommended for up to 120-130HP engines. The available reduction ratios are 2.03, 2.34, 2.5. SPG-4 has higher gear module and thickness, a little bigger body, about 2LB heavier than SPG-3, RR up to 3.16, recommended for up to 180HP, high torque engines. There is a German (BMW) rubber damper between the gear box and the engine. The propeller moment of inertia up to 9,000 kg/cm2. Rotax-style propeller hub, propeller shaft with a hole so it can be used with variable pitch prop or for glider towing. It is possible to use these gearboxes for both (tractor and pusher) layouts, install it up, down and any degrees left or right on the bellhousing.

SPG3 for GEO and Subaru

The body consists of 2 bolted down parts: 1) gearbox with the gear and oil inside + damper housing 2) mount plate (bellhousing) and crank-damper coupler. BMW damper and hardware included. Bellhousing and coupler are different for different (Suzuki, Subaru, Nissan, Honda etc.) You can see SPG-3 sets for GEO (left) and Subaru (right)

The gearbox life-time is 1000-2500 hours (depends on the engine power and the prop moment of inertia). The manufacturer advices to change bearings after 1000 hours. More than 900 SPG-2,3 and 4 gearboxes have been made since 2000. Some of them have 1300+ operating hours. This system is well proven. My customers and I have never had any problem with these gearboxes. I have never even opened one. One of my customers opened one after about 250 running hours. "Looks like new inside" - he said me.

Dimensions and weight data:

SPG-3 Metric Imperial
Offset (dimension between crank and prop shafts) 80mm 3.15"
Gearbox length (no bellhousing) 240mm 9.5"
Engine-prop flange dimension* 300mm 12"
Propeller hub Rotax standard**
Gearbox weight 7.5kg 16.5Lb
Full conversion kit weight* 11kg 24.2LB
*For Suzuki-Geo G10 and G13, can be a little different for other engines.

SPG-4 Metric Imperial
Offset (dimension between crank and prop shafts) 90mm 3.55"
Gearbox length (no bellhousing) 230mm 9"
Engine-prop flange dimension* 290mm 11.5"
Propeller hub Rotax standard**
Gearbox weight 8.5kg 18.7Lb
Full conversion kit weight 12kg 26.5LB
*For Subaru EJ, can be a little different for other engines.

**Adapters can be ordered for other shape of propellers
Conversion kit weight data provided for the complete bolt on kit consists of gearbox, damper, bellhousing and hardware. The data can vary slightly during the production and depends on the engine model.

I actually build and fly trikes with Geo-Suzuki engines converted using these kits.

Different GEO-Suzuki converted with SPG-2(3):

Air Trikes sells SPG-3 and SPG-4 conversion kits for Subaru EA and EJ:

I decided to make a new page with addresses and feedbacks from some people using our products (including engines and SPG-2 kits) for their aircraft. Look FEEDBACKS PAGE HERE

You also can see more pictures of airplanes with SPG converted engines at my "Simple" photo gallery. I hope they can help you to create your own design. CLICK HERE if you want to see them.

Air Trikes new R&D work with BMW R engine conversions

I never considered my auto converted engines as "alternative" or "cheap" way of aircraft engine development. Quite the contrary, automotive companies spent hundreds of million dollars for their new engines. We all know about serious competition in this industry for the last decades. As a result, even being cheaper because of mass production, modern auto engine is way more advanced than "real" aviation engines. It is a pleasure for me to design new conversion systems and fly them.

What about motorcycle engines? BMW 2-cyl boxer always attracted me. Everybody knows highest BMW quality, but not all know BMW company was one of the pioneers in aviation engine industry. I and II World War fighters and bombers fly with BMW engines. Light and compact air-oil cooled BMW boxer looks much more "aviation" than most sertified steam-age piston engines we fly now. It is more expensive than Suzuki-GEO but easy to instal under a cowling of most tractor-layout planes. Takeoff company in Germany makes aviaconversions of BMW R1100 and 1150 engines. They are well known and popular in Europe. Regardless the high price (about the same as Rotax 912), hundreds of light panes fly with BMW conversions in Europe.

This is SPG-2 based conversion of BMW R1100S. It is a little lighter, more compact and less expensive than German version. 99HP and only about 170LB included 40amp alternator, starter, radiator, ECM... This engine was running at my test trike. Unfortunately I didn't finish this work (motormount, mufflers) or have a lot of time in flight with this engine. I hope to finish this work when I have more time. Air Trikes is ready to supply SPG-3(4) conversion kits, BMW 1100 and 1150 engines like this to the customers. It looks like a good alternative to 912-912S, especially if you need a flat engine to put it inside a cowling but bon't want to lay Suzuki down and Subaru looks heavy for your project. Look at the pictures below.

Can SPG conversion kit be used for other engines?

Yes it can. You see the the Corvair engine on RagWing Stork RW-20 with installed SPG-2 and 73" KOOLprop. This conversion was done by Murray Green from Rosetown Sask. Canada. He noticed increasing of all performances comparatively with direct drive he used before. From his letter to me: "I couldn't be happier. The gearbox and prop seem to be made for the Corvair engine. A wonderful combination."

Look for some pictures I got from Brazil. Trike builders there are used SPG-2 to convert Honda engines they had. The projet is finished and sussessfully flys now. The last picture is a new Russian automotive engine converted with SPG-2. I think it is possible to convert any auto-moto engine up to 200HP using SPG-3(4) kit with custom made or modified adaptor plate and crank coupler.

SPG systems, conversion components available and other useful pictures:

I also decided to make a new page with addresses and feedbacks from SPG-2,3,4 buyers. You can ask them about the item and service quality. Look HERE We sold quite a lot of gearboxes but I didn't keep customers' addresses. Waiting for your feedbacks now.

Two-Stroke Engines

General information.

Converted motorcycle and snowmobile engines are also very popular. It is not a secret for example that Rotax 2-stroke UL engines are conversions of Ski-Doo and Sea-Doo motors. A lot of ultralight or hovercraft builders all over the world use such conversions. A lot of redrives exist for them.

5-V redrive system is designed especially for snowmobile engine conversion. This classical system consist of two 6061 T6 aluminum pulleys for 5 V-belts, eccentric shaft with heavy-duty closed ball bearings, motormount plate and all machined parts, rubber elements and hardware necessary for engine installation. It can be made at most of machine shops. I used this redrive with licensed Rotax 640 from 1998 like a powerplant for my "Frigate" trike. It has been installed now with Rotax 503 on my "Eagle" trike. This system has a lot of advantages comparatively with other redrives:

a) Very reliable. Will be working with 4 or even 3 belts. You don't have to be so worried about your belt condition like with your single belt drive.
b) Very light and less expensive comparatively with gearboxes.
c) You can use not only provision-type Rotax but also non-provision. You don't need to convert the engine itself.
d) Spare belts are easy available and not expensive (Car Quest XL serie).
e) Reduction ratio can be easy and smoothly changed by changing the pulley diameter.
f) The engine can be installed head-up or down.
g) This system can be easy adjusted by changing some installation dimensions to almost any project.
h) Quick (a couple of minutes) and easy adjusted belt tension.
i) It is a whole conversion unit included a motormount plate and 4 metal-rubber silentblocks. You need nothing but muffler and prop for your engine installation on a trike or UL plane.

This system is available now as a set of drafts (12 sheets plus description).

For additional information and order E-mail:, Use both addresses. Even if there are temporary problems with one, we will get your E-mail anyway.
Address: Air Trikes Enterprises
2241 Place de Belvedere
St. Lazare Quebec J7T2B1 Canada
Phone: (450) 202-7772