There is no doubt in my mind that there aretwo classes of engines, on the one hand youhave your top line well proven brands whichmaintain their place in the market for good rea-sons, and for those that want them it is moneywell spent. On the other hand, for the averageconsumer the ideal combination is an econom-ically priced engine that also has a good mea-sure of quality and other ancillary features aswell as the reliability and longevity that youshould be able to expect.

THE ENGINEEnter the SPE 40cc gas engine. The guys at

Precision Aerobatics have been working direct-ly with the manufacturers through the develop-ment of this motor for some time, and havemoulded it to their specifications. The reviewengine turned up in a well packaged box withall the required mounting stand off brackets,backing plate, ignition system and boltsrequired for installation. The most surprisinginclusion was the muffler as this is usually anadditional and sometimes expensive purchase.The crankcase is cast alloy and the cylinder isnicely machined and houses a ringed piston.No surprises there.

The ignition is a self (auto) advanced CDIunit and runs off a 4.8v to 6v power source.The manufacturer recommends the 4.8v andtesting proved there was plenty of spark withthat size pack. The CDI uses a magnetic insertin the shaft with a proximity pickup mountedoff the crankcase. This is easily rotated to adjustignition timing, and then locks into place witha 3mm cap screw.

The carburettor is made by ZAMA, theworld’s largest manufacturer of two strokediaphragm carbs. They have made 90,000,000carbys to date and boast some high perfor-mance and reliability. I suppose they wouldhave it right after making that many units. Thecarby company is Japanese so the quality iscertainly there as well as the know how. Thecarb supplied on the engine does not have achoke, but a quick search on the internetrevealed that they are available as a bolt onunit from ZAMA if required.

INSTALLATIONWell I’m no Airborne ‘Engin-Ear’ so I ain’t

pulling this motor apart, or I might have toenlist Brian’s help to get it back together.Instead, I’ll do what I do best - strap it to thepointy end of a ‘plane and fly it. The luckyplane was my trusty 27% Edge 540 (also fromPrecision Aerobatics) that had logged over 300flights. The installation was very simple andstandard. With the standoff brackets bolteddirectly to the mounting feet on the motor. Ichose to leave the alloy plate off as I didn’t seethe need for it and it seemed to be additionalweight with no pay off in this particular instal-

lation. If weight was not an issue, then usingthe backing plate would possibly making theinstallation of vibration dampers easier, butagain in my view, completely unnecessary here.

With this particular installation I decided togo for a slightly different method for the throttlelinkage, one I have seen used by some giantscale IMAC guys. Rather than a push - pull rod,I used a pull cable that pulls against the springthat closes the butterfly. I am not necessarilyrecommending this set up, as I am yet to be con-vinced of its merits but it certainly worked okayfor me, so I can’t discredit its functionality. Inorder to achieve this I had to make a small armout of carbon fibre to reverse the action of thebutterfly lever. From there the pull cable wentstraight back to the throttle servo and connectedboth ends with ball links. The ignition systemwas much the same as any other to installation,foam was used to isolate the unit from vibrationand all the electrics were kept as far from the Rxelectrics as possible. A heavy duty switch har-ness with charge jack was installed and a1200mAh 4.8v Ni-Cad battery pack was used forpower. As usual, Loctite thread compound wasused on all the bolts and where possible, Nylocknuts with spring washers.

The plumbing set up was much the same asany other gasser, the fuel pickup in the tankwent straight to the carby via a tee branch to astandard fuel dot and a gas proof filter, all runwith 1/8” gas line and a small zip tie wrappedaround every connection to ensure a leakproof joint. I no longer go for the flashy checkstop valved fuelling connectors as a simple teeand fuel dot work just as well and add lesscomplication to the system. The vent line wasrun from the top front on the inside of the tankto the bottom rear on the outside of the tankto prevent spillage and siphoning then exitedout the bottom of the plane. On a new tank setup, I give it a small pressure test to ensure nonasty surprises!

I always run a motor up prior to fitting thecowl to allow tuning and timing adjustmentsand in fact often leave the cowl off for the firstfew flights so I can readily see if there are anyproblems developing. Sometimes this can helpcatch leads or cables rubbing on things thatthey shouldn’t or things going astray that youwouldn’t see with the cowl on. The propeller Iwent for on the initial test runs and flight was aJXF 21x 8 wooden prop (also imported exclu-sively by Precision Aerobatics). The hub con-nection for the prop was a little different than

what I’ve seen previously, with a centre boltproviding the primary connection and two ofthe six circumferential bolts intended to gothrough the prop to provide protection againstrotation. I elected to use four of the six bolts forthis purpose, but care was required to preventover tightening and damaging the internalthread. The propeller was drilled to suit theabove configuration, balanced both ways, andfitted along with the spinner. Lastly the featherweight muffler was fitted using the two boltssupplied.

STARTINGA standard mineral based two stroke

oil/petrol mix was used at a ratio of 32:1. Amineral oil doesn’t burn off as much as syn-thetic and while being less efficient, does helpto carry out excess metal that comes off duringthe break in period. At this point I must say I

missed having a choke. Nothing drags fuel intoa carby quite as effectively as blocking off theair intake. That being said, it was no real prob-lem for me to put my finger over the hole andturn it a few times (with the ignition off!!) towet it up a little. From there it was only a mat-ter turning the ignition on, half a dozen flipsand she was away. The sound was quiterespectable, not that chain saw noise that sometend to turn on, and with only a small adjust-ment to the timing a smooth idle was achieved.I was quite impressed with the low amount ofvibration and this was typical at all RPM. Onthe initial run, a top RPM of 6210 was achievedwith this prop.

FLYINGI ran several tanks through with the engine

on the rich side before leaning it out a little andsending her skyward. With all systems proven,and the review preamble complete, the Edgewas taxied out to the flight line and the throttlepushed forward. The engine performed surpris-ingly well in the air, lugging this 84 incherthrough a vertical, and over the top quite well.Hover was achieved at about half throttle or soand pushing the stick forward would pull it outeven if a little sedately. If anyone was consid-ering this as a combo option, and kept every-thing as light as possible (i.e. Li-Po pack, miniservo on the throttle, simple plumbing etc),they would have even better results. The goodthing I found with this combination is that Icould throw the plane into any manoeuvre withhigh rates and full power and not break it. Thiswould make it ideal for anyone who was look-ing for a good first gasser - giant scale combi-nation. My Edge weighs at a little less than14lbs and the motors all up weight is similar toan O.S.160 two stroke to give you more of anidea. As for me, I will be keeping this motor inthe edge 540 as the pros out weigh the cons. Ibelieve that Precision Aerobatics will be offer-ing this plane with the 40cc as a combinationfor a little over $1200 which is an awesomedeal for any one needing the plane and powerplant combination.

CONCLUSIONAround six years ago, I purchased a cheap

Ryobi weed eater with a 23cc two stroke for$150 and have used it around my lawns nearlyevery weekend since. In that time I have had tore tune it twice and change the sparkplug once.Every time I go to use it, it starts, and doesn’tquit till I turn it off. My point? Even some of themore economically priced engines can prove tobe sturdy and reliable and in this case you havethe other benefit of the fact that spare parts willbe accessible through PA. While this particularengine is not an expensive big brand motor,there is no reason why it wouldn’t serve you forsome years to come given the right attentionand care, and when you consider it is pricedconsiderably less than some comparableengines, it is definitely worth a look. The vibra-tion levels were very low and throttle advancenice and smooth. All in all I was more than justa little impressed by the beastie and I’m sureyou will be to. This engine (and plane) is avail-able from Precision Aerobatics, Sydney,www.precisionaerobatics.com

Oh yes, its 26cc baby brother is due forrelease about the time this goes to print.