YakMad Posted December 13, 2012 Share Posted December 13, 2012 Rusty, Just a thought did you remove the carb at any stage, maybe to turn it around to suit this installation, as I managed to crimped the 'O' ring inside the manifold on one of my ASP's when I was swapping the carb around and it took an age to sort out, a new 'O' and the engine was back running as normal. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 13, 2012 Share Posted December 13, 2012 Posted by Rusty C on 13/12/2012 07:29:56: ..... Now that I am back at the factory settings I cant see how I can go wrong. Ah....such trust & innocence is very touching...... Well I think we're getting close Rusty.....if it runs with the glow stick attached this would point to a rich mixture & maybe this plus a slightly too cool engine is putting the fire out......get it good & hot before you try for the correct settings.....methanol takes a lot of heat out of its surroundings as it evaporates & if the engine is too cool the glowplug will stop glowing & spoil the party......remember that in a 4 stroke the glow plug has to keep glowing all on its own between firing strokes for much longer than in a 2 stroke..... Also, when you post piccies please can you remember to pop a "new line" between each pic.....otherwise the site seems them as being side by side & mucks up the page formatting...... Final thought.......I think you are very brave putting that nasty smelly oily model aeroplane down on the bed......lesser men have been banished to the shed for a whole winter by SWMBO for such reckless deeds.... Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 13, 2012 Author Share Posted December 13, 2012 YakMad Yes you are spot on bud Thats what happened on the first installation, I noticed fuel bubbling out the seal, Which was replaced and I also put an extra one round the outside much better. Steve I think your on the right track here, How long should I be waiting before removing the glow driver? I was not leaving it on to long as my one is on its way out! so I have just took delivery of a new much big capacity along with my new OS F As for the "factory settings" is this where to start or should I go back to the fuel tube and blowing into it way? as they seem to be a good bit apart ie air flow. Sorry about the pics I was not aware of the ill effects that caused Rusty Oh and yes I was pretty brave for bringing the model into the bed room, But she had pitty on me as the conservatory was freezing !! and thats where the camera lives anyway It wont happen much I bet Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 17, 2012 Author Share Posted December 17, 2012 Well I got some success today the engine seems to run well the air bubbles have gone I am not sure where the problem was cured but who cares. Should I always expect the motor to splutter and die after a long idle say 3 mins or so, I am not really sure what I am to expect of the engine thats all. overall its a million percent better that before, still a little bit lumpy on the transition but I am scared to touch any more as its ok when its been out of idle for a few seconds. rusty Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 17, 2012 Share Posted December 17, 2012 Great news Rusty.....It should bop away at idle pretty much as long as you want it too....no time limit....What sort of rpm is it doing? Can you put a tacho on it? Also what prop.....if it dies after a long idle I would suspect a slightly rich mixture....does it splutter a bit as you open the throttle.... Quote Link to comment Share on other sites More sharing options...
daniel barton Posted December 17, 2012 Share Posted December 17, 2012 my suggestion is to turn the high end needle in 1/4 turn, that ahould sort out the idle for you Quote Link to comment Share on other sites More sharing options...
Les Littleton Posted December 17, 2012 Share Posted December 17, 2012 Hi Dean. If you have checked the fuel line and are still seeing bubbles then it could well be an air leak around the 0 ring on the high speed needle . I had a very similar problem and solved it with a little fuel tube to seal the needle where it exits the carb . Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 17, 2012 Author Share Posted December 17, 2012 Steve I dont have a tacho I have just been doing it by ear and feel, I would guess its idle is around 2500 rpm. To which you are going to tell me to get a tacho right? Its turning a 13x6 apc I have others to try if need be though. Yeah it does seem to splutter after a long idle and sometimes dies on real quick application of throttle. Are you saying rich low end or high, Or even both? rusty Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 17, 2012 Share Posted December 17, 2012 By ear & feel is fine Rusty....I don't often use a tacho either.....if it feels right then it probably is but you do get people who try & set the idle incredibly low & then are amazed when it stops!!! 2,500rpm is probably about right....even slightly high. 13x6 APC is what I have on my ASP70....it seems to suit it very well..... How have you set the main needle? 4 strokes have a less well defined "peak" than a 2 stroke so its easy to set them just to the lean or rich side of ideal.....experience is your main guide here so maybe get someone to check the top end tune if you have access to a Guru..... OK...a couple of things to try.....will it idle OK ie for more than 3 minutes with the glow still connected? Second thing is to let it idle & then pinch the fuel line to the carb to cut the fuel supply......if it dies immediately its a touch lean....if it speeds up before cutting out its too rich.....usual caveat about keeping your fingers out of the way!!!! I'm tempted to think its a tiny bit rich myself but it gets very hard to be certain as you get it very close to perfect.....the odd tweak either way & see if it gets worse or better is often a good guide Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted December 18, 2012 Share Posted December 18, 2012 If you are happy with the way it runs at full throttle I would leave the high speed needle well alone, I agree with Steve it does sound a little rich at idle, try adjusting the idle 1/8th of a turn at a time. I must admit I've not used Steve's pinch method, I must try it out. I just go on the basis that if it cuts cleanly on opening the throttle it's lean, if it chokes up it's rich. Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 18, 2012 Author Share Posted December 18, 2012 Hey guys I would like to leave the high alone also as it is good where it is using said pinch test and nose up attitude. Steve I think it is stiil to fast at idle as the airframe is creeping down the strip which is not even close to its normal short cut. Would this suggest a rich low end with the barrel open to far to compensate for the lak of air? thoughts on that would be great. I am still not happy to put her into the air yet I want to make sure I get the best chance of getting her back, I have only simulated dead sticks with my pulse 25 E and it glides forever Something the AT-6 will not I guess. Quote Link to comment Share on other sites More sharing options...
David Davis Posted December 18, 2012 Share Posted December 18, 2012 Fast idle can occur when the servo is not moving the lever on the carburetter as far as it should. Is the throttle barrel fully shut when you have the stick fully back on the transmitter? If so is the throttle trim as far back as it can go? Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 18, 2012 Author Share Posted December 18, 2012 David I have setup it up on the throttle cut button. But with the stick right back the barrel its about 2mm open, but to get it to idle I have to trim up and I think the barrel is now open around 3mm maybe a touch more. This seems too much to me after years of 2 stroke car tuning, But this four stroke game is beating me at the momment rusty Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 19, 2012 Share Posted December 19, 2012 The idle speed of the engine is determined by the opening of the throttle barrel.....where that is doesn't really matter as long as it idles at the right speed. If it won't idle at the right speed then the idle mixture is wrong.....simple as that really. If it is creeping down the strip then it's probably idling too fast......close the throttle barrel a touch further to reduce the speed....if it cuts out then you will need to tweak the mixture a little bit more I'm afraid......the "pinch test" at the lowest idle speed you can manage should give you an indication of which way to go either richer or slower......my 2p is on it being a touch too rich. BTW I should have mentioned that the "pinch test" is best used at idle speed....trying at full throttle won't tell you much.... Always worth remembering to use all the tools at your disposal too......if you can't get the idle speed right down then try it with the glow attached....if this works then its almost certainly too rich.....(the final settings must be established without the glow attached however as this will change the idle characteristics)...........our engines do speak to us but it can take some experience & a bit of trial & error to understand what they are saying...... Do make sure its fully up to temp before fiddling as mentioned earlier......it can take a while in this cold weather.....Oh & have you checked the valve clearances too? Any issues here are more likely to be apparent at lower engine speeds......you should aim for a clearance (engine stone cold) of 0.1mm or 40 thousandths of your finest inch in old money..... Quote Link to comment Share on other sites More sharing options...
Lee Smalley Posted December 19, 2012 Share Posted December 19, 2012 the throttle on a four stroke will generally be more open than that on a two stroke at idle, unless its an airbleed version Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 19, 2012 Author Share Posted December 19, 2012 Steve The idle speed just now is all that can be achieved without it spluttering to a halt, So I would think your right about it being rich. However last attempts to lean at this point resulted in no idle until the throttle was advanced further which I couldnt get my head round. when I was pinching it at WOT It was rising in rpm slightly before stopping, this I the desired effect yes? and same at low end I guess? In earlier attempts I think my problem was that I to focused on the throttle open position at idle and was adjusting the low needle to get it to run which did not work well I did check the tappets before and after its first bench run and they where well slack when I got it so tightened them up, But as I did not have any feeler gauges I use a piece of paper which I thought would be near as damn it. Any thoughts here? I am holiday as of tomorrow so I will try again weather permiting Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 20, 2012 Share Posted December 20, 2012 H'mmm....I don't think the paper-as-feeler-gauge is a good idea....paper is very compressable & certainly won't help you set the tappets correctly.....a set of feeler gauges from the car acessory shop would be pretty cheap & worth getting I think. Tappet clearances are very important for good running.....too tight & they can close up when the engine gets hot which will stop the valve closing fully and prevent it sealing......too slack & the valve opens later & closes earlier....again...not good. These sorts of problems do tend to magnify at low engine speeds.... If it splutters to a halt rather than stops dead then this is usually a sign that its slightly rich......does keeping the glow attached help here at all? How far the throttle barrel is open at idle really doesn't matter.....you can't see it in the air after all.........as long as it idles cleanly & picks up nicely then its fine......the idle needle controls the mixture NOT the idle speed.....using it to control the idle speed means the fuel mixture you are supplying is incorrect....its quite common to have to close the throttle barrel slightly to reduce the idle speed as you get the idle mixture dialed in..... Just a couple of quick thoughts too....can you actually close the throttle barrel fully? I ask because its possible to screw the idle needle so far in it actually stops the barrel from fully closing....if this is the case you have a very lean mixture!!!.... Also how old is the engine? Its not uncommon for a new engine to take an hour or two's running in before it will idle correctly. Final thoughts Rusty....I think you are pretty close to getting it set up now.......I'd revisit the valve clearances if only to eliminate them as a possible problem area & then it might be as well getting a Guru from your club to see what he thinks.....the best guy to ask is someone who turns up & flys (unless he's a lekky flier obviously.....).....the guy constantly fiddling with his engine is best avoided..... Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 20, 2012 Author Share Posted December 20, 2012 Steve When I was setting the tappets up I was doing it in such a way that the paper could be pulled out easily so I dont think they would be far enough out to cause any bother, But I will buy some gauges soon when I next get to halfords or the likes. The engine runs fine on the glow, when its removed it dies but not instantly it more a slow death. you can almost here the blood in its throat gurgling then thats it. This Is why I was worried about the orientation of the motor sounded like it was pooling up. As for the engine age I had it running for a long time on the bench 5 8oz tanks at idle which felt like an eternity. I dont think its a mile away now but its real frustrating as the final touches seem to be really sensitive. If it does not happen soon I will need to think about either getting a different 4 stroke or putting in a 2 stroke as I want to have it air worthy for boxing day! rusty Quote Link to comment Share on other sites More sharing options...
stuey Posted December 20, 2012 Share Posted December 20, 2012 I'm not sure 5 tanks on idle is running it in properly. It is normally done on full throttle with a very rich mixture to control the speed, and leaned out gradually. This might mean your engine is still very tight which makes sorting out the idle harder imo. I thought the pinch test was for setting the idle. I use my tacho to set the top end needle, slowly leaned out until max revs then richened to drop at least a few hundred rpm. I think it might be worth trying the running in again, I have the instructions from just engines if that helps. Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 20, 2012 Author Share Posted December 20, 2012 Stuey The run in process with the full throttle and crazy rich setting I dont agree with, 2 and half turns is way plenty at a throttle position to suit a nice lowish rpm, couple of tanks at that then a half lean to start varying the rpm from idle to half. I belive that you want to heat it as quick as you can and a slobbering rich mix will not allow this. I know that car engines are of a different make up but, when I run them in I use wrist bands to cover the head, set the throttle to idle and use the low end to meter fuel, rich on start up then I lean and richen to maintain around 100 degrees on the head button, this way it reduces the bore tightness. Your could be right that it has just not done enough yet though, I may let it run at a fast idle for while more yet before turning screw again. Quote Link to comment Share on other sites More sharing options...
Steve Hargreaves - Moderator Posted December 21, 2012 Share Posted December 21, 2012 A couple of thoughts......As I understand it the SC instructions say to start the engine with the needle 5 turns open.....IMHO thats wayyyy too much......2.5 to 3 turns is plenty. However I'm inclined to agree with Stuey here in that I think you need to give the engine a bit more running in......the best method with these engines are short, rich runs initially with a cooling off period in between. Gradually weaken the mixture & lengthen the running time as the engine beds in. Its also a good idea to vary the throttle setting during this time from idle up to & including full throttle for short periods. Car engines are different in a number of ways....1) they are usually ABC engines rather than ringed (which the SC 4 strokes are). ABC engines need to get up to temperature quickly to ensure the correct fit between liner & piston. Running them too cold (ie slow & rich) can result in damage although its not something I've ever heard of. 2) car engines are usually lightly loaded by spinning a flywheel rather than a propellor (heavy load) 3) car engines spin much much faster.....peak rpm witll probably be in excess on 30 or possibly 40,000 rpm at full throttle.....I doubt your SC will see much over 10,000 rpm...probably less....a car engine with the throttle open just over idle speed will probably be turning over at 5-6,000 rpm......thats over half throttle for your SC70!!!! I think its probably worth running the engine in a bit more Rusty......a couple of tanks on a slightly rich setting varying the speed from idle to flat out will be time well spent..... Quote Link to comment Share on other sites More sharing options...
Rusty C Posted December 21, 2012 Author Share Posted December 21, 2012 Well guys I ended up taking the motor out of the AT-6 and back onto the test bed, After about 30 mins with a good warm up the motor is running to its best it will now idle till the cows come home! and even with an long idle snapping the throttle open the transition is great. I am really happy its running great as I was beginning to think I was losing it, I am no guru but I am not totally idiot as I have had engines in my blood since I can remember wether it was bikes,cars or rc cars. Anyway now that I can confirm that is a good un will tipping it slightly upside down effect it much, If so how? and why? rusty Quote Link to comment Share on other sites More sharing options...
Ian Jones Posted December 21, 2012 Share Posted December 21, 2012 If turning it upside down significantly alters the relationship of the tank to the carb position (i.e. makes the tank lower or more importantly higher) then yes it would be affected. If the mid line of the tank is inline with the carb then it shouldn't make any noticeable difference. Quote Link to comment Share on other sites More sharing options...
Cookson Posted December 21, 2012 Share Posted December 21, 2012 Rusty, see my post page 2, mine doesn't like being inverted. But having followed this thread with interest I have every confidence that I will be able to make it work and, I think, so will you. Some very good tips have come to light from some knowledgable people Quote Link to comment Share on other sites More sharing options...
Cookson Posted December 21, 2012 Share Posted December 21, 2012 Posted by Ian Jones on 21/12/2012 16:21:36: If turning it upside down significantly alters the relationship of the tank to the carb position (i.e. makes the tank lower or more importantly higher) then yes it would be affected. If the mid line of the tank is inline with the carb then it shouldn't make any noticeable difference. I have noted that on my Tucano the tank bung/centre line is about 1" higher than the carb !! Quote Link to comment Share on other sites More sharing options...
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