Jon H

Oh they are and I recommend a 46 to anyone with a 40 size trainer. But this model is saying 25-40 so I am guessing its about 50 inch not 60+ like the newer trainers and that makes a big difference. One model I used when learning to fly was a telemaster 66 with a span of...yup, 66 inches and it flew very well on an ancient enya 29. I have since flown one on an Irvine 40 and it was awful as it was just too much power, escpecially for my poor student as it kept running away. Granted the prop selection was not ideal but still, it was an issue and it eventually lead to the models end Another plus for a model with a little less power (not underpowered) is that it will teach better technique for things like go arounds. If they can just punch it out of trouble that's not always a great thing. Given that an instructor should be on a buddy box at this point an accident is unlikely. In any event, some more details of this specific model would be helpful

Regarding timing for Laser V twins there is an easy way to do it... each cam has teeth, and troughs between the teeth. You can count these to ensure the correct timing. So, for all V twins apart from the 360v the timing is as follows. VIEW THE ENGINE FROM THE REAR, turn the pinion drive so that the RIGHT HAND CYLINDER is at top dead center and POINTING VERTICALLY. Take one of the single cams (exhaust in this case) and look at it. If you sight down the centre of the cam lobe there should be a trough in the gear wheel. mark this trough on the other side so that when the lobe side is down you can still see it. Once done, and while holding TDC on the pinion, put the cam in so that its pointing at about 10.30 (imagine the hour hand on a clock face) when the right cylinder is vertical. Once in, count ANTICLOCKWISE from the mark you made and it should engage the pinion on the 6th trough. So, the twin cam. same deal but this time sight down centre of the the lobe FURTHEST from the gear wheel and mark it. (earlier twins have a tooth here not a trough so mark this instead). Now insert this into the crankcase as before but with the FURTHEST lobe pointing at about 1.30. This time count CLOCKWISE 7 troughs to where it should engage. if you have an older one with 1/2 tooth different on the timing and a tooth in the middle of the lobe then count CLOCKWISE so that teeth 6 and 7 partially engage with a trough exactly between them. Lastly the remaining exhaust cam. this is easy as it should point just to the left of vertical (you can see the lobe pointing up) and will count 5 troughs CLOCKWISE before engagement. Now the 360v is a little more challenging as the timing is not perfectly even, but using the same principals (and order) count 6, 6 and 4 respectively for the cams but count from the first tooth in the direction you are counting. you don't count from the centre of the lobe in this case UNLESS your twin cam has a tooth in the centre of the lobe furthest from the gear. see?? didn't I tell you it was easy I hope that makes sense!!!

Stalling is related to angle of attack/boundary layer separation and has nothing to do with engine power or speed. this why CAP232's etc tend to be flicky recovering from loops etc as the tips will stall flicking the model over even if the airspeed is high. As for the merits of cheap engines vs better quality ones then of course something higher quality will be better in the long term but ASP 36's are very cheap and you could buy at least 2 for the price of one OS. I agree that you want to try and get an engine to fit a series of models, but in the event that it is not possible to do that as it would compromise one model or another then buying something cheap and cheerful is perfectly fine. I had an asp 36 for over 8 years before it finally died. Also given that this is a trainer it might have an argument with mother earth at some point so a cheaper more disposable engine might be a good idea? If we were talking about a lovely 1/4 scale tiger moth or a really nice model then sure, go for the best you can get (I would use a laser 180 in my tiger moth example), but for a trainer its about doing the job. Some more details about the model might help, if its the size/weight of a tutor 40 then a 46 is a great idea but it sounds smaller than that to me, hence my suggestion

After over 20 years in this hobby and having flown most types of fixed wing model I am a firm believer that the approach recommended in that article is totally wrong for numerous reasons like additional expense wasted and a model that is (potentially) more difficult to fly. how many times have you heard a flyer complain his model 'wont slow down' for landing?? often this is caused by over powering as well as factors like the wrong propeller choice (too much pitch). It is often claimed a model will fly better with more power, this is not always the case. It should also be noted that most kit manufactures over spec their engine recommendations so that the model is guaranteed to fly. As I commented on another post, if (for example) a 60inch spitfire quotes 70-90 4 stroke then 70 will be plenty for scale flying, 80 gives a reserve if you get into bother, and 90+ is for toy aeroplane performance. Yes you can use the throttle, but how many people actually do? So, in answer to your question I would buy a cheap Chinese 36 two stroke (ASP SC etc) and use it for the trainer, then buy another engine later. I suggest the 36 as its easily a match for an old 40 and yet is not much larger/heavier than an old 25 so you should not suffer other problems with c/g or fit in the bearers etc. Finally the idea of 'dead weight' in lead never made sense to me. If you need a power of 10 (units not important) to fly the model, and your engine plus lead gives that and it flys well, adding an engine of power 15 with no lead makes no difference to the way the model flies unless you go faster that you did before. so the bigger and heavier engine is no improvement, you still have weight that is 'dead' and an engine is a lot dearer than lead Edited By Jon Harper on 06/05/2014 14:45:22

The method I use on the ASP engines is to pre lubricate the engine through the crankcase breather, plug hole and the rockers. I then get it started and run it rich and slow for a few minutes to warm it up. After that bring it to a reasonably fast half throttle setting for a few minutes. After about 4 mins total run time I open up to full power and very quickly (no more than 6 or so seconds) tune the engine for about 90% of fully lean and then throttle back. Then every 30 seconds or so give it a 5 second blast at full power. The reason for this much faster run is to make sure the engine is a full operating temperature. if it is not then the various parts will not have reached correct expansion and so will not run in correctly. Also steel/iron (in the liner and ring) need some heat to run in/work harden etc etc. I will always use a small prop for this (11x6 on a 52 for example) and when running flat out make sure there is still some oil coming from the exhaust and the engine does not sound distressed. So far I have run in 3 engines the way the instructions say and 3 'my way' and the latter 3 were much much better with good springy compression. These have also maintained their compression where as the others have lost it over a few months for it never to return. It should be noted that Laser now do not even have a run in period. they just tell you to start the engine, warm it up, tune it for max power and fly. The only proviso is that full power is not used for more than 15 seconds at a time for the first hour in the air.

Interesting indeed, although it sounds as though he had a much more serious leak. One criticism I do have of ASP is the running in instructions are no good at all. I do not have time to write my preferred method now but if anyone is interested I can post it later

The engine sounds pretty sweet in the video but it was not at idle for long so its hard to tell. have a go at it, just remember how many turns you went in a given direction so you know how to get back to where you were

Engine selection is always a tricky one. It has to be said that most models are overpowered, especially scale models. Most kit manufactures suggest a range of engines to cover all bases. If its (for example) a top flite spitfire and they suggest 70-90 4 stroke then most likely the 70 would be scale performance, an 80 would be good for a little comfort and a 90 would be 'its a toy aeroplane look at it go zoooom' Then you get some crazy folks putting 120's in them....I used a 120 in an 80 inch hurricane and it was fine! Long story short, if you have a specific model in mind look at the kit, ask a few questions, and make a choice. But remember that the static thrust of a large engine can make landing harder, and the adage of 'it needs nose weight, a bigger engine is better than lead' is not usually true. the model will weigh the same no matter what engine/lead you choose, and if you need a power of 10 (units not important) for satisfactory performance and your light engine plus lead gives you a power of 10 and good balance, but you put in a bigger, more expensive engine with a power of 15 and no lead, but you use only 10 for the performance you want, you are wasting money on a big engine you don't need. not to mention added fuel costs and a big ugly thing hanging out of the cowl! Also quoted HP figures mean nothing. you don't run most engines (4 strokes especially) at those peak revs. Also a 4 stroke with a big prop might have lower HP but will pull much better because of its torque and larger prop. they also give better power (as in actual pull) in the first 1/3-1/2 of the throttle than a two stroke

I don't lap any of my valves, I have never had the need on my Lasers. I did give my enya 120 a little go but all I did was spin the valve with an electric drill and very gently pull it into the head. It got the carbon off a treat. But as a general rule I have never needed too. As for the slow run tuning it is usually at least 1 full turn rich on all asp engines when new, I suspect that is so that people don't run very lean straight away. The method I use for slow run setting is to set the top end for max revs, throttle back and if rich (as we suspect) lean it off by 1/4 turn. Then stuff the throttle open, don't be a girl about it, jam it right open and see how it picks up. if it coughs and splutters its way up with smoke and hesitation throttle back, lean again and repeat. keep going until the engine bogs down or stops when you stuff it open (you should see a significant improvement before then). When you get to this point start to richen the slow run 1/8 turn at a time until you find the good setting. retune the top end again, recheck the bottom, fly. I would estimate that 90% of dead sticks are caused by poor tuning. It should be noted that a cdi ignition (as in a petrol) will keep the engine running even with bad tuning, this is why petrol engines seem more reliable. Most people do not take the time to set up their engines fully and as a result they are unreliable as a glowplug will go out if the tuning is wrong. I have not had a glow engine stop in flight for at least 4 years. it could be longer, I just cant remember!

12x6 would be my choice for this engine. 11x8 might load it too much and give you a high landing speed.

oh yea, beware using any harsh abrasive on the valves. ASP valves are not very hard and anything serious will eat them up. That's what happened to my friends 70 and my 400 radial. The bronze valve seats wore a groove in the head of the valve. Any attempt to grind it just did more damage to the valve.

I would not consider it duff, as I said its a cheap engine an they are built to a price. it all comes down to the QC and quality of materials. You don't get what you don't pay for unfortunately.   Anyway, I learned to fly on a puppeteer! great model, although I bet its well over gunned with a 70. the one I flew (my dads) had an old OS 48 surpass and eventually a 52 surpass. More than enough power. I currently have the legionnaire and its great fun on an ancient saito 45. Regarding your fast idle, make sure the slow run needle is correctly set (if the idle is fast but smooth, and stops if you throttle back further, its lean, fast but lumpy and spluttering then its rich) and see if that helps any. It should idle at about 2200-2500 tops. I use mostly laser engines and any idle above 2000rpm is not tolerated with 1500-1700 being the norm. if your prop is wooden you could swap it for a nylon one as the weight will help the idle, you could also use a heavy brass prop nut to give a flywheel effect. Also given the excess of power you most likely have take a look on hobby king for the turnigy TYPE A wooden 15x5 and give that a go. My Laser 70 takes it to over 9200rpm and I have loaned it to a friend for a 6th scale 1/5 strutter. With the large diameter it works well even though its a light prop. It must be the type A series as they run much faster than other props. I am using the 13x5 type A on my saito 45 and still get over 8000. When I put it on my laser 70 it did 13000!!! i was a little shocked but boy did it sound epic! Edited By Jon Harper on 30/04/2014 16:05:01

I agree with E.D to a limited degree as it depends on how much of a leak you are talking about. if its a slight hiss when turned slowly then don't worry, if however its fizzing all its compression away, even when flicked fairly smartly, then clearly its no good and JEn should sort it out. A friend has an SC 70 that was leaking so badly you could not tell the difference between the valve springs being compressed and the compression stroke. needless to say it did not run very well. if you want a quality motor then Laser are in a class of their own with (in my opinion) Enya next up. OS have been doing some strange things in recent years and I feel quality has suffered a little but the V series seem good value but not as good mechanically as the old surpass series. The Alpha's are very expensive (for the most part). Saito also make great engines but do prefer high nitro fuel which is pretty costly.

With all Chinese engines of this type the valves/rings will leak. I have had 2 61's a 52, a 70 and the big 400 radial and all of them leak like sieves. They still run ok but after they all wore out or I sold them I replaced them with other things. The engines are built to a price and this is one of the consequences. That said, I recently ran in some ASP's 4 strokes for club mates (I ignored the instructions as they do not run in correctly if followed) and they have come in much better than any I have used before.

I really think a 90 is over kill. As an example I flew the hobby king Ki61 (70 inch span and about 11lbs in weight) on a laser 100 and it was perfectly powered. If this Zero has a flying weight of 6 or 7lbs then a 90 is excessive. The laser 80 would be great though if its 8lbs or more

At 5.5lbs a 90 four stroke will tear it apart, unless that's its current weight and not a flying weight? if the flying weight is 5.5 or 6lbs then a 70 will be fine. If its heavier then a larger motor may be required. Personally I think a Laser would be the way to go. A little more money than something from china but it will last forever.