Asp 91 2 Stroke Manual
Wow many thanks for all the responses, I am a definite fan of this forum,I will try and go through all the mentioned issues, thanks for the links as well, the on board glow makes sense and I like the way it actually Senses the temp rather than just where the throttle stick is, I will get that, as well as a new slightly hotter plug I think. It's a new engine tho fully ran in, and yes it's from just engines. Many thanks for all the help and look forward to saying its back up and running well.ModeratorI'm not sure a glow switch is needed Tom.ASPs are good reliable engines.I have lots (including a 91) & they all perform very well. As the other guys have said it seems like a lean run was probably the source of your problem.when tuning the engine maybe try & do it with a 1/3 full tank.this should ensure that the motor is always slightly on the rich side. A rich engine is likely to cough & splutter but unlikely to cut out.a lean one will often cut dead!! Thanks Steve, I think your right, going through all the details I think it may of been too lean, it is running a just engines silencer as well I think that may of changed the needed mixture more than I think. Will get the next model sorted and report back.Posted by Steve Hargreaves - Moderator on 12:32:06:I'm not sure a glow switch is needed Tom.ASPs are good reliable engines.I have lots (including a 91) & they all perform very well.
As the other guys have said it seems like a lean run was probably the source of your problem.when tuning the engine maybe try & do it with a 1/3 full tank.this should ensure that the motor is always slightly on the rich side. A rich engine is likely to cough & splutter but unlikely to cut out.a lean one will often cut dead!!Steve just out of curiosity, what would you recommend my mixture needle be set at once Its back up and running? Prop was a 13-8 I think.ModeratorThe best needle setting is the one that makes your engine run properly.All engines are different so settings will vary. Fuel, plugs & engine installations all have an effect on the needle setting but for what it's worth I think my 91 runs on about 1 1/4 open or thereabouts.It really is worth taking some time to set the mixture properly, both high & low end. A good tip is to ensure the engine is fully warmed up before you try & set the needle(s).this can take some time especially in colder weather. Make sure the engine is good & hot before you start to tune 2-3 mins on about half throttle should do it. Once set then you can pretty much forget about it unless you change the fuel/plug/installation.
I rarely touch the needles on my engine. If set correctly there's just no need. If you get stuck ask the club expert.clue:- he's the one who turns up, starts his engines & flies.avoid the ones who keep fiddling with their engines.A 13x8 sounds good.a 14x6 works well too on a larger heavier model.Had a similar problem with a 2st ran fine on the ground then at take off went lean and cut. Found the problem to be a leaking o ring seal and loose clamp on the carb/crankcase seating.Sorry to hear you have engine troubles. Check all the pipe work from clunk to carb, pin holes ect.
Leaking o rings were a problem on a couple of my ASP engines. If you are worried about losing the needle settings. May be of helpI was asked to help a club mate with a similar problem on an ASP 61 2 stroke a while back.
All the signs of lean running and a very touchy needle setting which is unusual for these motors. My friend assured me that he'd double checked all the usual suspects and could find nothing amiss - in his workshop we stripped out the tank and my attention centred on the fuel line, it took a very circuitous route to the carb (at least a foot of tubing IIRC) and on removing it, we found that the tube's wall thickness was excessive leaving only a tiny bore.It was an awkward installation so we only managed to reduce the fuel tubing length by about a third, but did replace it with some decent sized stuff from my own stock.
Totally different situation after the change with the motor running well and holding tune.Don 't know what the model was (oldish Gangster type aerobat) but as it was bought from a club auction I wonder if the original owner got rid of it just because of the motor problems? Posted by Steve Hargreaves - Moderator on 21:04:59:The best needle setting is the one that makes your engine run properly.All engines are different so settings will vary. Fuel, plugs & engine installations all have an effect on the needle settingThis comment is spot on. Counting turns is generally meaningless and engines must be tuned individually.Also note that typically engines go rich in flight not lean and an engine that dies in flight because it has 'gone lean' has more than likely overheated so requires more cooling not more fuel. Posted by Steve Hargreaves - Moderator on 21:04:59:Also note that typically engines go rich in flight not lean and an engine that dies in flight because it has 'gone lean' has more than likely overheated so requires more cooling not more fuel.Would you care to expand on this please Jon, as the received wisdom that most of us labour under surrounds motors unloading in flight and running lean.When the engine unloads they actually go rich. Think about if you had an engine tuned for max power on a 12x6 prop, and you stopped it, swapped it for a lighter load 11x6 and ran it again.
Asp 91 2 Stroke Manual Download
It would almost certainly need leaning out. The same is true in the air.It was very clear when i was testing our 180 petrol prototype as the engine ran fine on the ground, straight and level and in a climb. But when in a dive at about 60% power it would start off ok and then start a rich burble as the speed rose and the engine unloaded. I leaned off the needle a tiny bit and tried again, problem solvedI'm not conviced Jon. My piped engines definitely show signs of leaning out in the air. My take on this is that at higher revs the carb will pass more air, ok this will in turn draw more fuel because of the increased pressure drop across the spraybar but as air has a lower viscosity than fuel won't airflow increase to a greater degree than the flow of fuel resulting in a leaner mix?Bob - or does the 'suck' I.E. The pressure drop in a venturi, increase as the square of the airflow speed through it, drawing relatively more fuel?
I've always suspected that the idea of speed leaning out an engine is a throwback to control-line days. My experience with RC is that motors in general neither lean nor richen with changes in speed (of the aircraft that is). But I have had exceptions.Graemeand in turn how does the fuel flow rate vary as a result of the increased pressure drop? I think I'll leave this one well alone, it's getting too theoretical for me I'll just stick to running a shade rich on the ground on the basis that I don't get many deadsticks or smoke trails working that way.The one exception being pumped motors, where I set them to peak revs on the ground.Tuned pipes are a different kettle of fish entirely as they dont just rely on the normal suction from the crankcase or cylinder. CL engines are also another story as they often used pressurised bladders instead of normal tanks. There are also some pretty serious centrifugal forces to deal with too.In general though, a standard non pumped or piped engine will go rich as it unloads unless the rpm change is massive.As i said before, most people mistake an overheated engine for a lean engine. If it ran fine for a few minutes and then gradually slowed down it is too hot and you need a better cowl design.
91.2 Patra
In general, a lean engine will protest more or less immediately but as always there are exceptions.Personally, when it comes to tuning i set all my engines to max rpm and leave them there. I dont do nose up tests as they are a waste of time and only lead to excessively rich mixture.
I have had only about 5 deadsticks in 6 years. Two were caused by dirt in the needle, one was my mistake as i set my idle trim incorrectly, one was a servo fault and one was fuel starvation. Cant say too much fairer than that!Edited By Jon Harper - Laser Engines on 12:58:14Thanks Jon, you've given me something else to think about. It does seem logical. An engine with loading decreased (@ same throttle position) will run faster therefore draw in more fuel and run richer. Something I had not considered before.
Personally, I believe prop unloading only happens in straight & level flight or a dive, not when climbing in any way. And usually at WOT.A 2 stroke (esp inverted) is more prone to flame-out due to the plug being doused by incoming cold fuel/air. A hot 4 stroke plug cures that with the only side effect being possible pre-ignition/detonation. Inverted mounts also need a leaner low end.I wonder what the OP makes of all this.Inverted two strokes can be a pain, but if they are tuned correctly at both top and bottom end they do improve a lot, and as you say you can use FS plugs or model technics do a longer plug for inverted engines that works quite well.As for the going rich business, there is a limit to this. If you really unload it, buy many thousand rpm it will go lean, but that's full throttle power dive stuff when using a small prop which is not the best idea under any circumstances!Just to lob in one other consideration, when you dive a model (ignoring the initial acceleration) doesn't the fuel head increase the fuel pressure, leading to richening, which may add to any venturi airflow derived effect?
Although Jon decries the traditional nose-up test, there's no doubt in my mind that a marginally lean engine will go leaner nose up.Glow engine carbs are simple devices and I know from experience that simply increasing the fuel pressure can lead to significant power increases with commensurate fuel consumption on some engines (if not all?)Personally, I do believe in doing a nose-up but I don't expect it to run lean as I hope to have tuned my engines correctly before doing so.