Roger Dyke Posted June 19 Author Share Posted June 19 Update: I have removed the engine from the plane and set it up on a bench stand. I have also received through the post, a brand new carb which is an ASP but is identcal (how lucky was that...). On the stand is a 6oz fuel tank with it's centre approx 1/4" below the carb spraybar. I initially set the carb up close to it's settings before installation. I've also installed a new ENYA 3 glow plug. The results are as follows:- The engine started first flick which was promising and ran it on about 3/4 throttle for about a minute to get warm. The high needle was about 1/4 turn adrift from optimum which was fine. The low needle was quite rich and spluttery so after leaning the low needle it settled down. With lots of time and patience I persevered for a good transition. Tickover is good at about 2600rpm for several minutes. The transition is still hesitant but not coughy and spluttery. If I move the throttle control from tickover to max over about 3 - 4 seconds, it picks up smoothly and fine, but if I was to just snatch it forward in about 2 seconds min to max then it's like it takes a big gulp of air and would die. I have done the "pinch test" and all sorts but now seems to be as good as I can get it. The new carb seems to be working far better than the previous carb (maybe because of the new "O" rings etc.. I was wondering, would the prop size be affecting things. I am using an APC 13x6 to keep the revs down to about 10k (because of noise). Just a thought. Quote Link to comment Share on other sites More sharing options...
Caveman Posted June 19 Share Posted June 19 Hi Roger, is your engine the same as this, with the large ‘circular’ carb? It’s an SC61, quite old bought from club mate for £10. It’s a really good engine. I have it fitted to a Panic bipe, using a 13x6 prop. It picks up really well with no hesitation and pulls strongly. The fuel is (very old) Southern Modelcraft 5% and the plug is an OS no.8 I’ll try to add a video so you hear it in action. GDB Quote Link to comment Share on other sites More sharing options...
Caveman Posted June 19 Share Posted June 19 Ha! Thwarted, the file size is too big and I’m not able to condense it at the moment. If it’s still relevant I can post it in a couple of day’s time. GDB Quote Link to comment Share on other sites More sharing options...
Roger Dyke Posted June 19 Author Share Posted June 19 Caveman: Almost the same but not quite. The cylinder case is not quite the same shape and the pinch bolt for the carb is on the front on mine whereas yours is at the rear (see photo). It pulls really well and is really powerful. It's peak RPM is 10,200 rpm on an APC 13x6 prop. and idles nicely now at about 2600 rpm. From a long tickover it is very slightly hesitant in the throttle transition (but no coughing and spluttering) if you are too abrupt, but the transition through the rest of the range now is really good. Quote Link to comment Share on other sites More sharing options...
Jon H Posted June 19 Share Posted June 19 Dont worry about the tank centreline as its completely meaningless as a measure as tanks vary in shape. As long as the top of the tank is in line with the carb centerline all will be well. The pinch test is also rubbish and of little value. The only way to set slow run setting is by leaning 1/8 turn at a time and testing the throttle pickup. Keep leaning until it wont pick up any more, then adjust back to perfect (or as close as possible). Total time required to start the engine and tune both needles from scratch, around 3 minutes. 10k on an engine that size isnt bad. You might get away with more blade though with perhaps a 14x6 at, i would hope, 9500? That would drop the noise. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted June 19 Share Posted June 19 Put an APC on, that'll reduce noise as well. Quote Link to comment Share on other sites More sharing options...
Simon Lumsdon 1 Posted June 19 Share Posted June 19 Have had similar experiences with poor throttle up on this engine, keep fettling the low speed idle and it should improve Quote Link to comment Share on other sites More sharing options...
Nigel R Posted June 19 Share Posted June 19 If you are brave you could try reshaping the low speed needle itself. Making the taper a touch blunter would result in a slightly richer mid range. Quote Link to comment Share on other sites More sharing options...
Roger Dyke Posted June 19 Author Share Posted June 19 Jon: Yes I have been nurturing the low mixture needle in a bit at a time exactly as you said and think I have now got it to it's optimum point. I think I am now reasonable happy with it. 14x6 eh! I might give that some thought. John: I already have an APC prop fitted. Simon: Yes, I think I am now in the right ball park. Nigel: If I was a younger man with better eyesight, I might have considered doing that. At my age though I think I'll pass on that one. Thanks for the suggestion. 1 Quote Link to comment Share on other sites More sharing options...
Caveman Posted June 19 Share Posted June 19 Hi Roger, I think that your engine is even older than mine as it has the crank bearing, if that the correct term, bolted to the engine case at the front, whereas mine is a complete casting. The carb on mine doesn’t have the black shroud on the throttle lever side. I don’t know if that’s intentional or it’s dropped off or rotted away! In any event it seems to work OK so I’ll leave it well alone. GDB Quote Link to comment Share on other sites More sharing options...
jeff2wings Posted June 19 Share Posted June 19 3 hours ago, Nigel R said: If you are brave you could try reshaping the low speed needle itself. Making the taper a touch blunter would result in a slightly richer mid range. I wouldn't do that if I were you, it's supposed to be parallel like on ST carbs What you have there is an original series 1 sc and caveman a series 2 the series 3 have square heads and rear mounted n/v ,and yes the series 1 were definitely known for being a bit tricky, had many asp/sc 2s and 4s and the later ones definitely a hole lot better, just persevere with it Quote Link to comment Share on other sites More sharing options...
Roger Dyke Posted June 20 Author Share Posted June 20 (edited) Nigel: I think that I'll leave the low mixture needle the way it is for now. My thanks to you all for all that the useful information. I purchased the engine new in about 1995 and it has given me good service. I can't remember it being difficult to control back then. In about 2002 I gave up model flying to attain my Private Pilots Licence. I continued flying the bigger planes until the end of 2018 when I reverted back to model flying. That's when I resurrected my old models which had been hanging up for years. I suppose over all that time the "O" rings etc., in the carbs had been hardening, pipes clogging and all sorts. Anyway, they all had a full re-furb with new pipes, tanks and electrics etc., but not "O" rings. I appreciate that the MK1 version is probably the worst of the 3 but was always a great performer. I have just installed a brand new carb on the engine (yesterday) and it has transformed it beyond words as to what it's been like since coming back into the hobby. I think that I am okay now. It's not perfect (it never was) but is as good as it's ever going to be and I think that I am now reasonably happy with it. Edited June 20 by Roger Dyke 3 Quote Link to comment Share on other sites More sharing options...
GaryW Posted June 20 Share Posted June 20 (edited) 9 hours ago, jeff2wings said: series 3 have square heads and rear mounted n/v , I had to move the main needle on my series 3 SC 52 to direct into the carb due to it being mounted on a panic using an original panic type engine mount Edited June 20 by GaryW Quote Link to comment Share on other sites More sharing options...
Roger Dyke Posted June 20 Author Share Posted June 20 Gary: You've answered a question there. I was wondering that if I chose to install another engine, what the chances would be of moving the rear needle valve to the front carb position. Thanks for that. 1 Quote Link to comment Share on other sites More sharing options...
GaryW Posted June 20 Share Posted June 20 (edited) 1 hour ago, Roger Dyke said: Gary: You've answered a question there. I was wondering that if I chose to install another engine, what the chances would be of moving the rear needle valve to the front carb position. Thanks for that. Normally on rear needle SC Engines theres a blanking plug on the side of the carb where needle valve would otherwise be,, all you need do is remove the blanking plug from the carb... Remove rear mount from the crankcase & unscrew the nedle valve body from the rear mounting bracket and screw the needle valve body straight into the carb Edited June 20 by GaryW Quote Link to comment Share on other sites More sharing options...
Roger Dyke Posted June 20 Author Share Posted June 20 Gary: Thanks for the conversion info. I'll bear that in mind if I start looking for another engine. Quote Link to comment Share on other sites More sharing options...
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