Skylark ultralight engine.

Eatherbreather · November 12, 2014

G'day all!

I have what I think is an Aussie made "Skylark" ultralight aircraft engine. It's taken me a full 12 months just to get a name for this otherwise unmarked engine. I'd like to run it for a bit of fun but I'm not sure mine is complete in the ignition department. It also appears to have been subject to some modifications - i.e. the addition of a pull start that is almost certainly a "Victa" part, the flywheel is most certainly marked "Victa"!

The only info I have been able to find is the tiny bit of info at this site where I think what is the same type of engine is pictured;

http://victoriancollections.net.au/items/51085d662162ef0e30b5463f

Has anyone got any info, parts or manuals that I may buy, borrow or copy? Amusing anecdotes or other info for this type also welcome.

Any and all help is greatly appreciated.

Jimbo ~ eatherbreather.

planedriver · November 12, 2014

G'day Jimbo. Got me stumped on that one. Hopefully someone on here might be able to throw some light on it's origin.

Might be worth asking the same question to Briggs and Stratton who I believe own the Victa business these days.

Rgds Planey

PS

It could be the 170cc twin motor that Victa imported from Canada around 1975

Downunder · November 12, 2014

An RCEXL model aircraft ignition system would probably run it nicely.

These are small and light with auto advance. Use a small battery pack (4.8v) and use a hall sensor/magnet pickup.

They generally come with 10mm cm-6 plug caps but others are available.

I did have the manufacturer make a custom ignition to suit a particular plug a few years ago......

Eatherbreather · November 12, 2014

It could be the 170cc twin motor that Victa imported from Canada around 1975?

G'day there!

I measured the capacity of this engine some time back and if my memory is correct it is 330cc total? I thought it might be a Victa twin too but it isn't I'm sure.

The pull start on it and probably the flywheel are modifications made to either make the engine go in lieu of missing original ignition parts or perhaps to "convenience" the operator. I know trying to pull start a Victa mower with no decompressor will just about pull your arm off when it fires and is very hard on the pull start cord - it will break in a very short time. I can't imagine the pull start fitted to this engine would have been any good either at twice the cc's of a mower and still no decompressor, it can't have been "convenient" at all. Also my specimen appears to have had it's engine mounts altered or replaced entirely to acomodate the installed Victa parts. A suspicion I held before I saw and supported by what I can see of the engine shown in the link.

I don't think this is a "Victa", it's just got some Victa parts fitted to it. I am prepared to be corrected however.

Thankyou for your interest.

Eatherbreather · November 12, 2014

G'day there!

Yes I have considered the use of an Rcxel ignition system - I actually have one here for another engine project. I may go this way if I need to but at this stage I'd prefer to have the engine make it's own spark by finding and fitting the bits it was meant to have - this has got to be part of the fun! : )

Presently the engine has a two lead coil, the two spark leads, the Victa flywheel and some sort of electronic looking module thingo - maybe a condenser? - It's about the size of a postage stamp. I haven't pulled anything apart yet but as far as I can tell it doesn't have any points although I imagine it should have/did originally.

Thank you for your interest.

Robert · November 13, 2014

Is it anything to do with the twin cyl lawnmower victas brought out years ago ??????

November 13, 2014

I put up a photo of the brochure here in this thread.

http://www.recreationalflying.com/threads/skylark-2-stroke-motor.11145/#post-111459

in 2010. Looks like you may have one. Have never seen a manual for one even when they first came out. Good find, a piece of history.

obad · November 13, 2014

G'day all!I have what I think is an Aussie made "Skylark" ultralight aircraft engine. It's taken me a full 12 months just to get a name for this otherwise unmarked engine. I'd like to run it for a bit of fun but I'm not sure mine is complete in the ignition department. It also appears to have been subject to some modifications - i.e. the addition of a pull start that is almost certainly a "Victa" part, the flywheel is most certainly marked "Victa"!
The only info I have been able to find is the tiny bit of info at this site where I think what is the same type of engine is pictured;

http://victoriancollections.net.au/items/51085d662162ef0e30b5463f

Has anyone got any info, parts or manuals that I may buy, borrow or copy? Amusing anecdotes or other info for this type also welcome.

Any and all help is greatly appreciated.

Jimbo ~ eatherbreather.

Hi, I purchased a skylark engine of the type you describe around 1982 to fit into a Mitchell wing U-2. It was constructed in Melbourne I believe from mainly Victa parts. It performed okay until after five hours The Crankshaft developed a crack in the weld which bonded the crank pin to the crank web. No damage to the aircraft however I then ordered and fitted at Konig three cylinder engine which gave excellent service.

If I remember correctly this engine was advertised in Airsport magazine so if you could locate some old ones that may be of help.

If my memory springs to light with any more information I will post it.

rankamateur · November 13, 2014

some sort of electronic looking module thingo - maybe a condenser? - It's about the size of a postage stamp.

Is it green, that sounds like an aftermarket ATOM ignition module, in which case it replaces the need for points.

Eatherbreather · November 13, 2014

Is it green, that sounds like an aftermarket ATOM ignition module, in which case it replaces the need for points.

I still need to have a closer look - at a glance it's actually not as I remembered - it's more like a rectangular module thingo about the size of matchbox split vertically along it's length. It may very well do the same job as the "Atom" module you've mentioned which is great because it may mean my engine is more complete than first imagined - it may even be entirely complete : )

Thankyou for your input.

Eatherbreather · November 13, 2014

I put up a photo of the brochure here in this thread.http://www.recreationalflying.com/threads/skylark-2-stroke-motor.11145/#post-111459
in 2010. Looks like you may have one. Have never seen a manual for one even when they first came out. Good find, a piece of history.

You sir are a champ! One pic really says a thousand words -and most of them say something like "OMG I thought the pull start was some homemade cobbled together junk, I can't believe it left the factory like this"! Apart from the angled carby mount shown in your brochure pic my engine is identical! Actually my cylinder heads appear to be very slightly different too - mine having an extra cooling fin on each side.

Also viewers should note that the red paint on my engine was added by the previous owner many years ago when he was a teen because " he thought Holden red would look good". I am reluctant to disagree with him!

Many thanks for your input.

November 13, 2014

It was a good attempt back when there weren't to many options. The U2 was a really nice aircraft. Would have liked to have one, still would.

bexrbetter · November 13, 2014

Is it green, that sounds like an aftermarket ATOM ignition module, in which case it replaces the need for points.

ATOMs came in different colours for different spark advance.

I used to fit them during my first apprenticeship (Yamaha motorcycles, Stihl Chainsaws and a range of mowers).

FWIW, this engine configuration is is known as a "Twingle" as both cylinders fire at the same time as a single cylinder. Also the crankcase reed induction (probably a Yamaha DT125 reed) is well ahead of it's time, possibly even a "First", but very practical for that configuration.

rankamateur · November 13, 2014

My only Atom is Atom green, same colour as my chainsaw post boring attachment, didn't realise they weren't all Atom green. Learned something this morning, thanks Bex, done my duty for today!

Eatherbreather · November 26, 2014

G'day all!

Bit of an update for you here. Minor disassembly of the engine to get a look at the ignition has revealed the coil to be a Victa twin coil and the other part is a Victa module.

I swapped the module with another Victa module of unknown heritage and still had no spark. I tried another type of module called "Nova" (which is presumable similar to the "Atom" but of much more recent manufacture) also of unknown heritage and still no spark. I had the coil tested at a mower shop and they said they had trouble fitting it to their machine but should have gotten something out of it - but again no spark with them either.

I reckon my coil is dead. It certainly seems to confirm what I was told almost 20 years ago and have read again recently on the net about the Victa twin mower - these coils are very probably the worst coil (or part outright?) that Victa ever made. It was largely the reason for the demise of the Twin mower, along with high production costs no doubt. The rear cylinder would quickly end up with a weak spark and soon after, no spark. Victa even fitted a a domed higher compression piston to the rear cylinder to try to help (not sure how it would). Hardly aviation material! Eventually a "revised" coil was produced apparently but I've seen and heard nothing of these.

Anyhoo, it looks like I'm going to be fitting my Rxcel ignition after all. I need to know the ignition timing for this engine. If I get stuck I'll go with the Victa 160cc timing which is given as 3mm before TDC (easily converted into degrees). The Skylark engine has exactly the same bore and stroke as the Victa 160cc. It wouldn't surprise me if it uses the same pistons too. It does however have a significantly higher compression ratio I think. I think this affects combustion rates and in all probability therefore the ignition timing too. Any ideas anyone?

I have found "28" stamped into each crankcase half if this helps anyone.

http://pickersyard.weebly.com/ I found some "Atom" modules at this site. Mine are on their way.

I was gonna upload some more pics but the server says no for some reason : (

Downunder · November 26, 2014

Rcexl systems run 26 to 28 degrees btdc. This is what you use to set inital (static) timing on the hall sensor.

The automatic advance will retard the spark until about 3000 rpm from memory.

This should get your engine working at least. All the RC engines with rcexl pretty much run these figures.

I developed a kit (first one) for owners of these systems to set and test these ignition systems themselves. Previously owners had to return their engines to the dealer. The chinese engine manufacturers were banging these systems on their engines without setting them up properly causing alot of warranty returns and a few crashes all because the timing was out.

oh yeah, remember that it is the point at which the magnet LEAVES the hall sensor which is the exact firing point.

Methusala · November 26, 2014

I had one of these back in 1981. Sourced from a bloke called, I think, Ron Lang from Dandenong. It was fitted with a cog tooth belt re drive and used Victa ignition and a Tillotson 'pumper' carb. It functioned for about 5 hrs until it broke the crank. I was lucky to land the Pteradactyl in a cow paddock - sure scared the cows! When questioned about the cause of the crank failure, Lang answered that he "probably omitted to instal a spacer washer on the crankshaft. It was a brave attempt back in those days but in reality it should have remained on the ground if not as a boat anchor. Regards, Don. PS. It also was fitted with Victa de-compression valves to help starting.

facthunter · November 27, 2014

From memory the Victa twin was all alloy and a bit of a failure. Sunbeam took over Victa (Mowers). They do fire together so you can employ a coil that is not earthed and fire two plugs together that way through the body of the motor via each plug. Use nearly 30 degrees advance at full advance. You can utilise the original Victa crank with a centre section pressed into the flywheels which should be ONE PIECE made like a disc with two pins set at 180 degrees from opposite sides, hardened to take the big end rollers. looks like the cylinders are cast iron with that motor (as the Victa was). The original Victa rods are fine. Nev

November 27, 2014

I had one of these back in 1981. Sourced from a bloke called, I think, Ron Lang from Dandenong. It was fitted with a cog tooth belt re drive and used Victa ignition and a Tillotson 'pumper' carb. It functioned for about 5 hrs until it broke the crank. I was lucky to land the Pteradactyl in a cow paddock - sure scared the cows! When questioned about the cause of the crank failure, Lang answered that he "probably omitted to instal a spacer washer on the crankshaft. It was a brave attempt back in those days but in reality it should have remained on the ground if not as a boat anchor. Regards, Don. PS. It also was fitted with Victa de-compression valves to help starting.

The name Ron Lang rings a bell. I remember it from the MAFA 'Contact' mailing list

Eatherbreather · November 30, 2014

Thanks for your continued interest guys!

I have gone the Rxcel ignition route. I worked out that "Victa" timing (for their 160cc single mower) is 23 deg btdc so I have set mine there. Downunder do you suppose this is correct or should I opt for the 30 deg that everyone seems to use when converting model glow engines to petrol?

The machining involved was pretty straight forward, the result being what I liken to being a "record player" arrangement - that is the magnet is mounted in the face of a rotating disc passing under a fixed Hall sensor pickup that is itself mounted at 90 deg to the shaft. Timing is adjusted by loosening the starter cup and the two grub screws that secure the magnet housing disc to the shaft then rotating the disc to the desired position.

The fitting of the ignition gear after the machining is a breeze. So simple, neat and tidy. I reckon it has a far more sophisticated, RELIABLE, lightweight and better shielded ignition now than it ever did. I have no plans to fly this engine in anything but if I was to do so I'd take this new Chinese ignition over the old stuff any day, even though the manufacturer specifically said not to. I expect this admonition is more for their benefit than mine

Any thoughts on the correct spark plug to use? I've put a couple of plugs in it (NGK BP6ES) that were working perfectly when removed from my Mini Moke whilst chasing an ignition problem there. These plugs have exactly the correct length of thread on them but as for the correct heat range for this engine I have no idea.

Attached are some pics for your amusement that show the new ignition being fitted. I apologise for all the cr*p in and around the engine. Only now have I noticed how cluttered it makes the pics.

Made the tool with dial gauge to establish T.D.C. and 3mm B.T.D.C. as per "Victa" mower timing. The portion of the tool threaded into the head is made from the bottom of an old dead "Victa" decompressor! I kept that part for years. I knew it would be useful one day! The other bits of metal picked up at the tip shop. I only had to add my dial gauge, two grub screws and some time on my lathe. Other pics show flywheel and other now obsolete parts removed including a small wooden wedge, very possibly fashioned from a clothes peg, that was used to jam the coil in place on it's "E" core (this engine came from a plane that crashed apparently remember). "Here's one I prepared earlier" - a small glow flat twin that I made some years ago, total capacity of 0.65cc. Also visible is an empty brown bottle that until recently contained an apple based "thinking juice". I'm not sure it works very well, but I'm going to keep trying it until it does

facthunter · November 30, 2014

Single carb (the only set-up realistically possible) on this type of engine, Can have a difficulty getting the mixtures even. I presume you are using reed valves? Nev

Downunder · November 30, 2014

Personally, I think 30 is too advanced. Heading into methanol engine timing. 26 to 28 will see your engine run on the RCEXL. Go from there.

Converted methanol engines are generally small and higher revving (10 000+) so 30 is perhaps OK there. Done a few Super Tigres. G51 petrol, G90 petrol, 2300 (on meth). These days the Chinese make small petrols cheaply so it's easier to buy.....

Not sure I would ever run a RCEXL in a manned vehicle. Had a couple fail. At the very least I would use duel ignition, duel plugs including duel sensors.

3W or DA would probably be better quality.......but still very EXPERIMENTAL.

Don't worry about the plugs. Just get it running and "read" them later.

I like the "half-moon" sensor holder....

Have you looked at the reeds? Wouldn't surprise me if they were cracked.....Carby kitted?

Being "Eatherbreather" I take it you’re a diesel fan too?

facthunter · November 30, 2014

Larger combustion chamber may make model engines timing not as relevant. Make it adjustable with the engine running It's often not that difficult to do, and you will soon find the best setting. Higher revs needs the more advance. Nev

Eatherbreather · December 1, 2014

Single carb (the only set-up realistically possible) on this type of engine, Can have a difficulty getting the mixtures even. I presume you are using reed valves? Nev

Yes this engine has reed valves. I figured it may be hard to get to get an even amount of fuel/air to each cylinder. There's not much I can do for that except to run it and see what happens. The flat twin glow engine I built has this same problem. I wonder if the problem might be resolved by the use of twin carbys on a piston ported twin cylinder engine?

Downunder · December 1, 2014

Yes this engine has reed valves. I figured it may be hard to get to get an even amount of fuel/air to each cylinder. There's not much I can do for that except to run it and see what happens. The flat twin glow engine I built has this same problem. I wonder if the problem might be resolved by the use of twin carbys on a piston ported twin cylinder engine?

Twin carbs would still flow to the same case giving it's own balance/syncro issues. Single carb and reeds seems to be the "modern" way....

Having said that, I've often thought about making a piston ported Zenoah flat twin. I've got a few stuffed, 2mm stroked cranks and 36mm barrels.....30CC singles..

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