# Engines to replace the dominance of Rotax

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#### rotax618

##### Well-Known Member
Just slightly heavier than 582 (abt 10lbs hand propped) approx 55HP, direct drive Suzuki G10.

#### Yellowhammer

##### Well-Known Member
It's been TWELVE YEARS since we started doing Yamahas on gyroplanes in 2007! The arguments made against trying them may have been valid twelve years ago but not in 2019.

By now there are well over a hundred Yamaha 3 and 4 cylinder 4-stroke water-cooled engines flying with ZERO failures over 12 years. I myself have several hundreds of hours on a single example, while there are many others who are approaching a thousand.

Steve Henry of Wild West Aircraft flew from Idaho for the fourth straight year in a row in a Yamaha-powered Highlander to Airventure and won GRAND CHAMPION at Oshkosh this year flying and competing in the STOL competitions - and winning every one of them, beating even the Draco turbine Wilga. His Yamaha Apex 4-cyl included my Mohawk Aero gearbox adapter conversion kit. Steve fabricates and sells the Highlander and the Yamaha HIghlander conversion kit parts including exhaust, intake and mounting frames for the Yamaha Genesis 4-cylinder (YG4) which comes from either the RX1 or Apex snowmobiles. I provide the gearbox, shaft coupling and adapters, as well as other parts such as cooling system components and wire harnesses.

The smallest stock YG3 puts out 120 HP at 160 lbs all-up weight, while the most recent 165HP YG4 EXUP builds I am currently working on for 2 customers (which also provides 30% more HP throughout the midrange, effectively making these engines altitude-compensating over other similar Apex's w/o EXUP valves,) weigh about the same as a Rotax 914 or 915 which cannot put out anywhere near this HP, even at the very short intervals allowed before turning into a flying grenade.

There is no factory-stock engine, including a Rotax, in the same weight category 160-175 lbs all-up that puts out 120-165 HP reliably and constantly, let alone just punching it momentarily for a few minutes like a 914 or 915 allows. I have had a steady stream of customers coming to me over the past five years who left Rotax behind because 1) it broke, 2) the carbs are junk 3) no power and/or 4) it costs five to ten times as much as a Yamaha YG3 or YG4.

We now have tens of thousands of fleet flight hours. Jump in, the water's fine.

My newest project for a customer in Nebraska is a Yamaha Sidewinder 200HP turbo-charged YG3, stock out of the box. Those engines are available for 1/3 the price of a Rotax 914 that puts out 115 HP for five minutes max and weighs about the same.

My last completed project shipping out this week is on the other end of the spectrum: a 2-cylinder, Yamaha Phazer 4-stroke, water-cooled, 80HP, EFI engine weighing 88 pounds, ~130 lbs with everything added on.

Feel free to contact me by email to Info@MohawkAeroCraft.com and I will send you a ZIP file with all the info you need to get properly informed and started saving thousands upon thousands of dollars, and getting REAL performance for a change.

We need to talk sir. I have a Pulsar I that I do not want to install a Rotax 582 on. I am currently building the plane and will be needing a power plant soon. I really like what I hear of the 2 cylinder four stroke Phazer engine. If I can get it to fit without having to reconfigure my cowling would be a plus too!

I already have the radiator and other bits for the 582 but just don't myself trusting the 572 very much.

#### Yellowhammer

##### Well-Known Member
Just slightly heavier than 582 (abt 10lbs hand propped) approx 55HP, direct drive Suzuki G10.
I like the hell outta that engine! I don't want to hand prop anything though.

#### rotax618

##### Well-Known Member
The Suzuki can be leaned over at 70deg without modification except to the sump and oil pickup pipe and can be leaned over 90 deg by adding an oil return tube from the valve cover to the sump.

#### mullacharjak

##### Well-Known Member
The 582 is a very good and relaible engine. The G10 suzuki car engine NA is comparable to the 503 engine.The turbo engine may be considered equal to a 582 at a greater weight.The torque is greater at a lower rpm.Someone in Australia installed a G10 with C gear box on Early Bird Jenny biplane and it flew well.A more compact engine than the G10 is Suzuki K6A and R06A.These are 660cc engines and 63 hp in the turbo versions.

#### rotax618

##### Well-Known Member
I did some experiments with a G10 engine built by Bilsam, the compression was raised and it had a cam grind, I don’t know what other modifications it had. The Bilsam gearbox was rubbish, it had rubber dampeners which were immersed in the gear oil which softened and dissolved the rubber blocks. The fuel injection did not work so I fitted a Bing CV carburettor. On my test rig the G10 would turn a prop pitched for my 618 Rotax around 100rpm more than the 618 at full throttle.

#### TFF

##### Well-Known Member
That’s the point of two stokes, strip all the weight of the little bitty parts like cam, valves, chain.

#### PMD

##### Well-Known Member
WAY back in the '80s when I built airboats, I switched from VW engines (I built everything for them - intake, exhaust, cooling, prop drives/thrust adapters, torsional dampers, etc.) that in direct drive were around 200 lb. thrust to Rotax 503s with gearbox that gave not only 300 lb. thrust, but freed up my time to build a LOT more ultra-light (commercial) airboats. Over those few years, I worked closely with Ron Shettler in Vernon BC on propeller stuff, and we contributed our ideas and experience with abrasion protection to props that they did in volume manufacturing with excellent results. BUT: the growth of the ultralight aircraft world was making those once-cheap Rotax engines start to cost over a grand a crack - so I started looking at alternatives. Since I need more power for some hulls, I built some 500cc triples with Star (Polaris' Japanese supplier) that would blow a liquid Rotax out of the water with ease...but the gearbox was the trick. I bought them from Cayuna in upstate MN - they outsourced those boxes, but I found they lived a long time behind well over 100HP 3 cylinder two cycle engines (bear in mind MUCH different torsional charactaristics from a 2 cylinder!!!!!) so started looking to them as a possible alternate for the smaller air cooled twins. When I went down to visit them, I saw a little flash of a 4 cylinder, 4 cycle drone engine they were putting into production for a military contract (thus limiting my access to seeing them up close). Anyone know what became of these engines? Think they would be right into 912 market size?

Also seem to remember they eventually left upstate MN and went SE somewhere as 2si (2 stroke international) part of AMW/Cuyuna. IIRC they built some 2 cycles up to 100HP that would spark ignite but run on gasoline, jet AND diesel fuel. This just seems to scream at me it is not just the engineering that makes an engine successful, it is some kind of magic in marketing that can scare competitors into submission.

#### Armilite

##### Well-Known Member
What four strokes are out there with the same weight as the 582? Or does such an animal exist?
Thanks for you're help!
==============================

For reference, a New complete FWF 582UL (65hp) 580.9cc setup is around $8000. A Rotax Rick 670 (92hp) 669.2cc is less than a New 582UL setup. Prices from CPS Website: ROTAX 912 UL | 80 HP ENGINE  1211.2 cc​ 73.91 cu. in.​$15,813.00

ROTAX 912 ULS | 100 HP ENGINE

 1352 cc​ 82.6 cu. in.​
$18,878.00 ROTAX 912 IS SPORT | 100 HP ENGINE  1352 cc​ 82.6 cu. in.​$21973.00

Now, we have these Honda/Clone Singles and V Twins. All the Big Block Singles are based off the Honda GX390 Engine (88mm x 64mm) 389.4cc, they just change Bores and Strokes. The Max CC Single Engine is (100mm x 86.5mm) 679.6cc / 12.3cc = 55.3hp@5000rpm.

A 460 Single is (92mm x 69mm) 458.8cc has been Dynoed making 37.37hp@5000rpm = 12.3cc to make 1hp.

A 420 Single is (90mm x 66m) 420.0cc Stock is 13hp@3600rpm. Upgraded, it has been Dynoed making 36.69hp@5250rpm = 11.4cc to make 1hp.

The V Twins that are useful HP vs Weight start out at the Harbor Freight 670cc (55hp).

Stock V Twins goes up to 43hp@3600rpm with EFI using 993cc! I know there is some HD Parts to upgrade them, but I haven't looked at them as much as the Singles account most Part 103's and most Small Kitplanes all fall into an MTOW of 540 lbs to 660 lbs, which require 25hp to 40hp. If the Singles can be Big Bored to 100mm, the V Twins can be also.

VanGuard 993 V Twin:
Bore 3.37 (in) = 85.598 mm
Stroke 3.41 (in) = 86.614 mm

If Big Bored 12mm like the Singles to 97mm = 1280.4cc. The Rotax 912 80hp@5500rpm is 1211.2cc!

The Koler V Twin: Price: $3,299.00 Bore/Stroke 3.5 X 3.1 in Displacement 999cc Max Power 37HP I would start with the lowest Cost 993cc: Briggs & Stratton Vanguard™ 993cc 35 Gross HP V-Twin OHV Electric Start Horizontal Engine, 1-1/8" x 4" CS, 20Alt. Model: 613477-0268-J1$2,744.99

You're going to Upgrade the Rods, CAM, Flywheel, CARB, Air Filter, Valve Springs, Locks & Keepers, the Exhaust, Billet Needle Bearing Rocker Arms, etc., anyway, and Mill the Head for a higher CR. If making more hp@5000rpm I would do all the Engine Coatings and burn 100LL. Adding a bigger Oil Cooler would help Cooling also. Upgrades probably $600 to$1000 depending on what you all do.

The Highest HP V Twin I have seen Stock is 43hp 993 Marine with EFI. But I don't see it listed now, 40hp max is all I see listed. You might Save money if they offer a Short Block.

If you figure for an Upgraded Engine, Avg 12.5cc to make 1hp at 5000rpm.
40hp x 12.5cc = 500cc needed.
45hp x 12.5cc = 562.5cc needed.
50hp x 12.5cc = 625cc needed.
55hp x 12.5cc = 687.5cc needed.
60hp x 12.5cc = 750cc needed.
65hp x 12.5cc = 812.5cc needed.
70hp x 12.5cc = 875cc needed.
75hp x 12.5cc = 937.5cc needed.
80hp x 12.5cc = 1000cc needed.

Rotax 912 80hp@5800rpm 1211.2cc/80hp = 15.14cc to make 1hp.

#### BJC

##### Well-Known Member
HBA Supporter
Are you asserting that all of those engines are close in weight to the 582?

BJC

#### billyvray

##### Well-Known Member
2SI (subsidiery of Cuyuna, a copy of the JLO engine) did take over that design, and made a decent attempt to expand the brand. I'm not sure what happened but they went out of business somewhere 2012-2014. They showed some cool modular type designs in various configurations. I have a 2SI 35 hp version of the old Cuyuna 202 with an oddball iginition that is now dead and un-servicable....sad.

WAY back in the '80s when I built airboats, I switched from VW engines (I built everything for them - intake, exhaust, cooling, prop drives/thrust adapters, torsional dampers, etc.) that in direct drive were around 200 lb. thrust to Rotax 503s with gearbox that gave not only 300 lb. thrust, but freed up my time to build a LOT more ultra-light (commercial) airboats. Over those few years, I worked closely with Ron Shettler in Vernon BC on propeller stuff, and we contributed our ideas and experience with abrasion protection to props that they did in volume manufacturing with excellent results. BUT: the growth of the ultralight aircraft world was making those once-cheap Rotax engines start to cost over a grand a crack - so I started looking at alternatives. Since I need more power for some hulls, I built some 500cc triples with Star (Polaris' Japanese supplier) that would blow a liquid Rotax out of the water with ease...but the gearbox was the trick. I bought them from Cayuna in upstate MN - they outsourced those boxes, but I found they lived a long time behind well over 100HP 3 cylinder two cycle engines (bear in mind MUCH different torsional charactaristics from a 2 cylinder!!!!!) so started looking to them as a possible alternate for the smaller air cooled twins. When I went down to visit them, I saw a little flash of a 4 cylinder, 4 cycle drone engine they were putting into production for a military contract (thus limiting my access to seeing them up close). Anyone know what became of these engines? Think they would be right into 912 market size?

Also seem to remember they eventually left upstate MN and went SE somewhere as 2si (2 stroke international) part of AMW/Cuyuna. IIRC they built some 2 cycles up to 100HP that would spark ignite but run on gasoline, jet AND diesel fuel. This just seems to scream at me it is not just the engineering that makes an engine successful, it is some kind of magic in marketing that can scare competitors into submission.

#### Vigilant1

##### Well-Known Member
==============================
Avg 12.5cc to make 1hp at 5000rpm.
Is there any history of an air cooled normally aspirated 4 stroke engine actually making continuous power at this 12.5cc/hp level in aviation service?

Folks should count on about 30cc per continuous HP for these engines. Some might get a little more, some a little less, the limiting factor is CHT. That's what has been found in actual airplanes in actual flight use.

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#### henryk

##### Well-Known Member
"SWISSAUTO" =4T /25 kg, 250 cc /35 HP =7 cc/HP...

#### Armilite

##### Well-Known Member
Are you asserting that all of those engines are close in weight to the 582?

BJC
=========================
These Honda/Clone Single come in three Classes of Cases, Mini(GX200), Small, Big Block. The GX340/GX390+ is the Big Block of the Singles. Once upgraded and with the HD Billet Aluminum parts with a Belt Drive, less than 65 lbs, what a Rotax 277F UL Weighs with a Gear Drive.

The Honda/Clone Singles are less Weight than the 582UL but limited to around 55hp by their CC, the Max 11.0 CR I would use, and the CAM used. The difference in weight between the original GX390 Engine (88mm x 64mm) 389.4cc, and the different Bores and Strokes. The Max CC Single Engine I have seen is (100mm x 86.5mm) 679.6cc / 12.3cc = 55.3hp@5000rpm. Your only talking about a few Pounds difference between the GX390 389.4cc and the Hybrid 679.6cc Engines if you use the same HD Parts. The Honda/Clone GX200's Stock is 6.5hp@3600rpm, used on this Lazair Ultralight are turning 5000rpm for around 15hp once upgraded. I don't think he Milled the Heads for a Higher CR. A Harbor Freight Predator 212cc is $99.99 when on Sale. He used a Clone 200cc Engine. Notice: 200cc/12.5cc = 16hp. The V Twins start out at around 470cc and go up to about 1000cc Stock. They all can be Big Bored for more CC which equals more HP. You have Small Block V Twins & Big Block V Twins. There all lower in Weight than the 582UL once upgraded with the HD Billet Aluminum parts. As I showed, to get the same 65hp x 12.5cc = 812.5cc is needed if turned at 5000rpms. Could you turn it 5500rpm, 6000rpm, 6500rpm, for even more hp, Yes? But you will have more Heat to deal with. Could you take a Smaller, Cheaper$800 Harbor Freight 670 and make same 65hp, Yes. But you would have to upgrade everything, probably do all the Porting & Polishing, Bigger Valves, maybe even a Big Bore if you want to keep rpm to 5000rpm, etc. Most of these Engines have Small Valves, Small Cams, so can be Upgraded.

For both the Singles and the V Twins you do about the same Upgrades.
1. Disable Governor & throw away parts, Weight you don't need.
2. Disable Low Oil Sensor & throw away parts, Weight you don't need.
3. Install Hi-Rev kit(HD Push Rods, Valve Springs, Keepers & Locks) for the Max Rpm you want to use.
4. Install a Bigger Carb/Carbs or EFI.
5. Install a Bigger and better Billet CAM.
6. Mill Head for Higher CR, Max I would use is 11.0cr.
7. Install a better Air Filter like a K&N.
8. Install a Tuned Header Exhaust.
9. Install HD Billet Aluminium Rod.
10. Install HD Billet Aluminium Flywheel.
11. Install Billet Lifters.
12. I would Install Billet needle Bearing Rocker Arms.
13. Since you really want better Quality than Stock Valves, I would upgrade to Stainless, you just as well go with the Bigger Valves also.
14. V Twins have an Oil Cooler, but for Plane use, I would with go Bigger one.
15. I would use all the different engine Coatings also.

----------------------------------->
16. You can take out the Balance Shafts and Save even more Weight, and just Balance the Assembly.

Most of these Upgrades and mods you can do yourself. There are all kinds of Video's on Youtube to show you how to do most of this stuff. These Heads are Aluminum. Most of these Engines Stock are 8.0-8.3cr for 87 Octane and to go up to 11.0cr is like Milling off .080". Carefully, with shallow cuts on just a Cheap Milling Vice on a Drill Press you can even do that. I know for the Singles there are people who sell the Heads with the Big Valves, Ported Polished fairly cheap on eBay.

ACE Aviation makes one of the best Belt Drives for these Singles and V Twins.

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#### Armilite

##### Well-Known Member
Is there any history of an air cooled normally aspirated 4 stroke engine actually making continuous power at this 12.5cc/hp level in aviation service?

Folks should count on about 30cc per continuous HP for these engines. Some might get a little more, some a little less, the limiting factor is CHT. That's what has been found in actual airplanes in actual flight use.
=========================

Your making Assumptions Based on What "should count on about 30cc per continuous HP for these engines." Are you turning that Engine 5000rpm Continuous, NO. Were not turning these 5000rpm continuous either! All Engines are rated at their max HP@rpm there designed for. Then they are throttled back for usually 75% Power at a certain rpm, not CC. His GX200's are making around 15hp each at 75% is 11.25hp x 2 Engines = 22.5hp. He even flew it on (1) GX200 Engine.

The V Twins start out at around 470cc and go up to about 1000cc Stock. They all can be Big Bored for more CC which equals more HP. You have Small Block V Twins & Big Block V Twins. There all lower in Weight than the 582UL once upgraded with the HD Billet Aluminum parts. As I showed, to get the same 65hp x 12.5cc = 812.5cc is needed if turned at 5000rpms. Could you turn it 5500rpm, 6000rpm, 6500rpm, for even more hp, Yes? But you will have more Heat to deal with. Could you take a Smaller, Cheaper $800 Harbor Freight 670 and make same 65hp, Yes. But you would have to upgrade everything, probably do all the Porting & Polishing, Bigger Valves, maybe even a Big Bore if you want to keep rpm to 5000rpm, etc. Most of these Engines have Small Valves, Small Cams, so can be Upgraded. For both the Singles and the V Twins you do about the same Upgrades. 1. Disable Governor & throw away parts, Weight you don't need. 2. Disable Low Oil Sensor & throw away parts, Weight you don't need. 3. Install Hi-Rev kit(HD Push Rods, Valve Springs, Keepers & Locks) for the Max Rpm you want to use. 4. Install a Bigger Carb/Carbs or EFI. 5. Install a Bigger and better Billet CAM. 6. Mill Head for Higher CR, Max I would use is 11.0cr. 7. Install a better Air Filter like a K&N. 8. Install a Tuned Header Exhaust. 9. Install HD Billet Aluminium Rod. 10. Install HD Billet Aluminium Flywheel. 11. Install Billet Lifters. 12. I would Install Billet needle Bearing Rocker Arms. 13. Since you really want better Quality than Stock Valves, I would upgrade to Stainless, you just as well go with the Bigger Valves also. 14. V Twins have an Oil Cooler, but for Plane use, I would with go Bigger one. 15. I would use all the different engine Coatings also. -----------------------------------> 16. You can take out the Balance Shafts and Save even more Weight, and just Balance the Assembly. Most of these Upgrades and mods you can do yourself. There are all kinds of Video's on Youtube to show you how to do most of this stuff. These Heads are Aluminum. Most of these Engines Stock are 8.0-8.3cr for 87 Octane and to go up to 11.0cr is like Milling off .080". Carefully, with shallow cuts on just a Cheap Milling Vice on a Drill Press you can even do that. I know for the Singles there are people who sell the Heads with the Big Valves, Ported Polished fairly cheap on eBay. ACE Aviation makes one of the best Belt Drives for these Singles and V Twins. Thank you brother! I have learned more from reading your replies than from any other source!!! #### PMD ##### Well-Known Member ========================= These Honda/Clone Single come in three Classes of Cases, Mini(GX200), Small, Big Block. The GX340/GX390+ is the Big Block of the Singles. Once upgraded and with the HD Billet Aluminum parts with a Belt Drive, less than 65 lbs, what a Rotax 277F UL Weighs with a Gear Drive. The Honda/Clone Singles are less Weight than the 582UL but limited to around 55hp by their CC, the Max 11.0 CR I would use, and the CAM used. The difference in weight between the original GX390 Engine (88mm x 64mm) 389.4cc, and the different Bores and Strokes. The Max CC Single Engine I have seen is (100mm x 86.5mm) 679.6cc / 12.3cc = 55.3hp@5000rpm. Your only talking about a few Pounds difference between the GX390 389.4cc and the Hybrid 679.6cc Engines if you use the same HD Parts. The Honda/Clone GX200's Stock is 6.5hp@3600rpm, used on this Lazair Ultralight are turning 5000rpm for around 15hp once upgraded. I don't think he Milled the Heads for a Higher CR. A Harbor Freight Predator 212cc is$99.99 when on Sale. He used a Clone 200cc Engine. Notice: 200cc/12.5cc = 16hp
Armilite: I have a lot of time with GX160 and GX200s in sprint kart racing days (still have some around - but our clubs are all B&S and Rotax now). We ran/run the little ones at 7,200 RPM, but were limited by rules to stock carb, cam, compression and muffled exhaust, so not a lot of net HP being delivered. I built one solo II kart with a GX270 that has big carb, tuned exhaust, etc. and it makes we guess around 15HP @ 7,000. What is singularly noteable is that in many, many years of racing, I have never seen anyone actually break one (wear out to the point of reduced power, yes, but big bang? never).

#### n3puppy

##### Well-Known Member
A O-200 will cruise at full rated rpm/power.
100hp@2750 rpm continuous rating
Continuous cc/hp = 32.9
TBO = 2000 hrs

912UL climb power 79.9hp@5800rpm (59.6kw)
Continuous 77.8hp@5500rpm (58kw)
Roughly a 2.5% power loss at continuous rating
Continuous cc/hp= 15.6
TBO = 600-2000 hrs depending on Serial number (upgrades)

RR’s 670 - max power 92hp@6350rpm
Max cruise around 60Hp @ 5500rpm
Roughly 35% reduction in power at max cruise.
Continuous cc/hp = 11.15
TBO = 300 - 450hrs based on upgrades installed

Honda GX460 Clone Single (from above graph)
Max power 37.37hp @ 5000rpm
Continuous power ??@????rpm
Power reduction max vs continuous = ??%
Continuous cc/hp = ??cc
TBO = ??? Hrs

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