View Full Version : kawasaki 440 fancooled engine,

joe nunnally
11-29-2006, 08:57 AM
Good Morning all.
I could use a little feed back concerning my 40 hp engine. I'm building a 3D RV drop keel gyro, and i'd like to use this engine if possible. The engine is equiped with a 2.6.1 belt driven reduction unit. Any ideas would be appreciated. Have a great day.

Thank you
Joe Nunnally

11-29-2006, 01:07 PM
Hi Joe !
could you post a Pic of your 3D RV drop keel gyro as I havn't the foggyiest idea of what that is <GRIN>
its been my limited experience that 40hp is minimal for a gyro to fly you will probly need to keep the gyro frame and all its goodies to the Ultralight weight limit of 254 pounds in order to fly the beastie with 40 hp... alot depends on the prop used and the rotor diamator as well ... and ofcorse the altitude your trying to fly at. my 40hp just barely can get my gyro off the ground at 4,800' ASL and that is with 26ft rotor diam.
at sea level it would no doubt fly fine with the thicker air, but up here its tough !
good to see you here Joe and welcome to the forem.

brett s
11-29-2006, 01:26 PM
I recall a few others over the years trying that engine on ultralight gyros & posting about it here or on the old forum, try this:


11-29-2006, 05:26 PM
Kawasaki 440 will NOT make enough power to fly a gyro.

joe nunnally
11-30-2006, 07:46 AM
To Bob, BretS, and GyroRon.
Thank you very much for the infomation . I think i'll look into another engine. Sorry i havn't any photos of the 3D RV.
I wish you all a very good day.

Thanks again
Joe N.

11-30-2006, 08:33 AM
Before you "throw the baby out with the bathwater" Check and see if
that engine will work first !
Just because a few guys say the power will be marginal means nothing !. you may be very light and the craft very light and it fly like a top with that 40hp engine....
seriously 40hp engines have been powering Gyrobees for years and it realy doesn't matter if the name on it is Rotex or Kawasaki or Suzuki... 40hp is 40 hp... gyros can fly with that HP with no problems...
if that happens to be an engine you already own I say use it and see if it will get you aloft ! it may well fly you fine and it may also never get you off the ground...

you are asking a question that we cannot possably answer correctly because we do not have enough information to make an inteligant desigon on it....
so Likewize, don't you toss out a good motor because You don't have enough info. on the siduation eather.

that engine may well work fine without any modifications of any sort , then it is just as likely that if it does fly it will be very marginal at best.... WE HAVE NO IDEA because we need to know the weight of the gyro the size of the rotor the size of the prop... with that info I can put it into GYROCALC.EXE and it will tell me if it will fly or not...
Do a surch for Gyrocalc and you can down load the program for free...its quite handy !

Good luck to you !


brett s
11-30-2006, 09:08 AM
I think the consenus is that engine doesn't really make 40 hp in the real world - the 447 does.

11-30-2006, 07:55 PM
It is a 35 horsepower engine. It will not fly a stripped down Gyrobee unless the pilot was a 100 pound woman.... A 3DRV is a drop keel Bensen, same as a single place Falcon without the fiberglass body, These are not light gyros and if the pilot is going to be 170 pounds or more than he will need at least a Rotax 503 ( 52 horsepower ) to fly it. A Rotax 582 would be the better choice for power.

But hey, if you want to build the gyro and install the kawasaki, go for it, Just don't think it will fly you.

12-01-2006, 07:10 AM
Well, flying a gyro with 40hp is marginal enough... if you lower the hp at all your probly not going to get off the ground
...a rotex 503 is just a hair bigger than the 447 rotex and only devolips like 2 hp more if i were you I'ed look into the rotex 582 or what ever their called that make 50 hp to 55hp
... there is nothing more flustrateing than trying to get a gyro to lift off when the engine just can't push any harder.... not to mention hadzardous you wind up takeing chances and those chances usually wind up with you wrecking the gyro,,, do it right in the first place and you'll be better off.


12-01-2006, 07:33 AM

Rotax 447 = 40 hp

Rotax 503 = 48 hp

Rotax 503 with dual carbs and dual ignition = 52 hp

Rotax 532 = 65 hp

Rotax 582 = 65 hp

rotax 618 = 75 hp

rotax 912 = 80 hp

rotax 912 S = 100 hp

rotax 914 = 115 hp

joe nunnally
12-01-2006, 08:13 AM
To everyone who replied to my post, Thank you. I'm building an ultralight aircraft as well,and i think i'll be better off in the long run to install the engine in the ultralight. I can't afford to replace the engine at this time, Fixed income! So if anyone's interested in a new single place rotor head ? I'll be selling mine. I wish everyone a great day.

Thank's again

Joe N.

12-01-2006, 08:50 AM
When Gyro Tech was first developing the Honey Bee, they tried using the "40 hp" Kawasaki to save a few bucks. I had the dubious honor of doing some of the test flying. Despite prop optimization and every other possible "fix", I could not fly the machine out of ground effect at a field elevation of 1000 MSL. This is not idle speculation, for when my own butt is in the seat I pay attention! Two weeks later, with a 447, it flew just fine.


12-01-2006, 03:31 PM
Well there ya have your answer for sure ! thanks Ralph !
... I hate to see ya give up on the gyro Joe ! however a fella has gott'a do what a fella has gott'a do ! <grin> I well know the income problem....
Good luck selling your Rotor head !
GyroRon :
I viewed your Ignored post just to see what you were fussing about now
and Your way out in left feild again guy, but engine specks can be viewed at....
these specs are from the factory for the verious engines in question (Rotex line)
Your memory is getting as bad as mine<grin> and you are telling a fella that a 503 is 52hp and nether version of the 503 makes that much HP... the 503 duel carb makes only 49.6 hp NOT OVER 50hp the 503 Rotex is the same motor as the 447 except it has bigger cylinders and pistons, it comes in single carb or duel carb. it is ment as a 45hp engine not 50hp as you keep saying.... if your going to give information please try to be acurate.... thats what you keep telling me to do ! Geez !
these Spec. sheets are quite informative, please read them before you correct people.
I'll get off the soap box now !

12-01-2006, 05:56 PM
Bob.... get off the transsexual web site and do a web search, or just search this forum. There has been different specs given for the same Rotax engines, from place to place. Leading edge airfoils is just a dealer for Rotax, they have their specs, CPS... Lockwood... and many other places also sell these engines and have their own specs too. I did not give out false information.

By the way, there is a big difference between a Rotax 447 and a Rotax 503, more than just bigger cylinders and pistons.

12-01-2006, 07:07 PM
Really Ron, they are exactly the same, besides the dual ignition, carbs, cylinders, pistons, crank, crankshaft and porting.

And last time I checked 49.6 was pretty close to 50.

Probably close to 52 if the weather is cool.:boink:

12-02-2006, 01:40 AM
hehehehe !
that don't leave much Scott ! <grin>
I could be wrong about that ! ...its possable, I doubt it but its possable... according to the specs the only thing diferent is the bore.... not the stroke, so technically if you wanted to you should be able to put 503 pistons and cylinders on a 447 and it would be fine. this is common among engine manifacturers.
Honda did that for a few of their motorcycles so did yamaha and Suzuki, you could switch the entire top end of the honda 250 twin with the 305 dream and have a 305 instead of a 250, or swap them the other way arround and turn your 305 into a 250....
the only way that is possable is having the same crank and vurtually the same engine, consiquetly when I see 2 identical engines with everything the same but the bore diamator the chances are extreamily good that you can swap parts !
what ever.... its not important anyway ! hehehe c ya !

12-02-2006, 01:59 AM
Goodmorning Bob

See you are still up and at it.

12-02-2006, 12:03 PM
Hiya Thom !
good to see ya !
Have you taken your RAF up lately ? you got one nice lookin' aircraft there !
Oh, You mentioned that you were thinking about raising the HS to be in the prop thrust a bit... I was wondering if you figured out a way to do that yet ? being back so far seems like you'll have some problems stablelizeing it if you raise it up say 15"
or so, not to mention being in the way of the rudder !
... so I'm courious, how do you plan on tackeling that problem ?
not to mention ya don't want down time ! HAHAHAH not on a bird that will fly ! <GRIN>

12-02-2006, 03:10 PM
It will stay in one place straight and level but I will cut the keel in two places drop the engine 6 inches. This will give me prop wash on both sides and will be in the strongest part of the prop. The tip. I will post pics when it happens. I will fly the 40 off before I do this mod. Then I will only have to fly off 5 more and I will be a legal eagle. Thanks for asking Bob. I had a leg cramp this morning so I was up for a little while and got on the net. I saw you were on but when I posted you had gone off.

12-02-2006, 03:41 PM
Hi Thom !
its a good idea to get the 40 off before ya do any more mods i think...
I think i understand what ya have in mind with dropping the keel and then the engine by 6" sort of make a "U" arround the prop to get the tail section back up where it is in the prop wash.
You might check about where the big portion of the wind comes off the prop before you do this... I know I was supprized at the shape of the thrust comeing off the prop at the tail. that is why I desided on raising the HS only 15 or 18" what ever it was instead of in to the center of the prop thrust line... as below that was alot more moveing air than in the center.... it seams my engine prop combonation at the time put out a nice tube of fast moveing air but the center was almost void of air pressure ! I amagon most props do that, but with my 3 blded prop on there it is mush less pronounced than it was... it was like a tube 1.5' to 2ft thick of fast moveing air with a hollow center
so I placed the HS below the center line in the center of that air stream .
sense then I have dropped the engine down again another 4" and changed the prop so it seams to have made up for it.
I was also carefull to cut my HS to be as wide as the tube of air off the prop, and sense I changed the prop the HS extends out about 6" to each side of the tube of air... I guess thats a good thing as relitive wind will effect it a bit more now
.... the problem with what you have in mind is getting the rear portion of the keel high enough to be inward of the prop tips by about 6" so you have full emersion of the HS, I don't know if you can pull it off but that would be something to shoot for !
I wish ya luck Thom and when ya do take that baby aloft please take some Pic's
keep the turnie side up !<grin>
C ya !