New bloke with a KFM112 engined Kitfox mk2

Hey everyone,

I'm from England and have just purchased a kitfoxmk2 with a KFM 112M engine in it.

The whole thing needs a complete rebuild but the engine is good and it has a brand new wooden prop which is gorgeous and lives under my bed.

I'm kind of assuming that this is a mainly Australian forum so your probably wondering why some random English guy has joined,

Well...

The reason is that I may need help or parts for the KFM engine and I know that Jabiru used them in their early aircraft so I reckon there is a fair chance that some of you may have bits, parts, knoweledge, photos, whole engines, etc.

Certainly more than I would expect in Blighty.

Any Kitfox flyers down under ?

Cheers,

Skelly.

Welcome to the club, Skellywelly. We welcome people from all over the world. Probably the closest member to you lives in Cannock and operates out of Otherton, near the M6 at Penkridge.

Aircraft are aircraft and there is a wealth of knowledge and experience here to assist you.

There'd be quite a few Kitfoxes about, but I doubt any with KFM engines in them. When they went out of production, Jabiru had to make their own engine. Even Jabiru's early engine is rare.. Still there may be some KFM's around somewhere. Good hunting. Put an ad in AVIATION Trader Nev

The KFM is a bit of an orphan I'm afraid. Might be best to sell it for what you can and use that cash to refurb the airframe. The jab 1600 then 2200 were the direct replacement for it. There are Kitfoxes around with the 2200 jab and one of the female writers of Kitplanes magazine owns one. I wouldn't think that the paperwork wouldn't be too difficult to change it over.

Ken

This is what they looked like:

http://www.buildagyrocopter.com/kfm-112-engine/

Hey everyone,

 

I'm from England and have just purchased a kitfoxmk2 with a KFM 112M engine in it.

The whole thing needs a complete rebuild but the engine is good and it has a brand new wooden prop which is gorgeous and lives under my bed.

 

I'm kind of assuming that this is a mainly Australian forum so your probably wondering why some random English guy has joined,

Well...

 

The reason is that I may need help or parts for the KFM engine and I know that Jabiru used them in their early aircraft so I reckon there is a fair chance that some of you may have bits, parts, knoweledge, photos, whole engines, etc.

 

Certainly more than I would expect in Blighty.

 

Any Kitfox flyers down under ?

 

Cheers,

Skelly.

Hi, I have an operating KFM in a Supapup and an amount of engine parts, e.g. blocks, cylinder/ head, some electrical. Would be keeping spares for Pup but may have some left ( don't need 12 spare heads). May be able to help with engine books. Loopy

Hi Loopy,

How cool is that..

I have a whole load of boring questions to fire at you regarding this engine.

I think I will send them in a private message as this thread will run the risk of drifting off into engine tech land.

Hope that's ok,

Cheers.

Skelly.

It’s good to post the questions and answers plus images as you sometimes get leads and additional information. That is the spirit and backbone of this great site. All things aviation chatter.

What's the set up with having opposite cylinders in line?. The only opposed motor s like that, which I know of have silly conrods with lots of offset. Nev

What's the set up with having opposite cylinders in line?. The only opposed motor s like that, which I know of have silly conrods with lots of offset. Nev

Are they?

Looks that way to me. If there's offset it's very small compared to other similarly configured motors. Nev

And probably less space for bearings.

Or both sharing a single crankpin which would be absurd. Nev

Or both sharing a single crankpin which would be absurd. Nev

-You mean like a Harley?

It's a V twin.. What horizontally opposed motor has a single pin.? Merlins are the same and a fork and blade rod set enables a non staggered cylinder arrangement (Expensive) A "V" twin can have an excellent even piston speed. Nev

Hi Guys,

Firstly @Thruster88 thanks for the photo, got any more ?

Now..

the KFM112 has offset crank pins and 3 main brgs.

So for example on any pair of opposing cylinders both pistons travel outwards and inwards at the same time due to the crank pins being 180 degrees from each other.

This results in a very well balanced engine.

One side of cylinders is set back by around 30mm from the other side.

Hope this helps.

Skelly.

Memories of a KFM powered Jabiru! In my logbook is my 2nd dual nav exercise in Jabiru 55-678, a KFM up front. They made about 50 HP as I recall. My task was to fly my CFI (and aircraft owner) from Pt. Pirie to Woomera where he had a couple of students, spend a few hours wandering around Woomera and then return mid-afternoon in about 30 degree heat. I vividly recall being at 2,500 ft. over salt pan country, full throttle and descending at 500fpm. The instructors advice was not to worry, we'll find a thermal soon. As a previous gliding CFI he knew what he was doing and sure enough, we soon ascended back to a respectable height. The KFM's sure worked hard in those early Jabirus, but the ones I knew were soon replaced by Jabi 1600's and then 2200's.

Here is a photo of the crankpin arrangement.

Well that worked well..

Lets try again.

Here is a photo of the crankpin arrangement.

You can see that both pistons are at TDC.

Cheers.

Skelly.

It doesn't show if there's any offset in the rods near the small end, The 3 main bearing set up allows less cylinder offset than Jabiru's 5 main bearings arrangement. That's why the Jab as a twin had too much vibration to ever be a proposition. Jabiru put one mainbearing between each throw which is good diesel practice but adds weight and makes the cylinders offset more, and makes the crank essentially longer and less stiff in twist. This would have been more of a problem with the 8 cylinder version which is discontinued.. Most aero FLAT engines don't run full counterweighted crankshafts because of the extra weight. This means the middle main bearing is highly loaded as revs go up. I can't see much wrong with that engine except it's probably too small for the job in some situations. Everyone whinged about it's price.. Having the barrel and head in one piece is fine till you have to work on the valve seats but it can be done as it is with most other aero engines of the aircooled kind. Nev

Hi Nev,

The rods have no offset, they are pretty short too.

The opposing cylinders are staggered by the thickness of a rod plus the bit of crank between them.

Yes, only 3 main brgs and direct drive.

I can imagine its a pain to replace valve seats as they are right at the end of the cylinder, Putting them should be easy but taking them out looks like a challenge.

Luckily its something I don't need to do anytime soon.

I must say I like the way the engine has no oil pick up pipe to vibrate and snap off, its cast into the crankcase instead.

Skelly.

On 8/22/2020 at 5:44 AM, skellywelly said:

Hey everyone, Any Kitfox flyers down under ? Cheers, Skelly.

Don`t know if I`m any help but there`s a KitFox with a KFM engine in it, sitting under a house, not far from here! the guy built it himself and he flew it from our property here at Deeral for several years! he`s now in his 80`s, not in good health and hasn`t flown it for a few years.

If you are on facebook I can put you in touch with him! you`ll find me here, on facebook https://www.facebook.com/franco.arri

According to the rumour mill, Jabiru made their own engine after the Israelis' bought up an entire years worth of KFM's production.

This would suggest that there could be KFM spares to be sourced in Israel?

@farriThanks, I have sent you a message on facebook,

@pylon500Wow, never heard that one, I am in touch with some people at IAME, I will ask and check.

I wonder what it would cost to ship a Kitfox from Oz to Blighty...

If you find anyone at @pylon500, it wont be me as I'm not on facebook