Tim Cheal Posted January 1, 2010 Share Posted January 1, 2010 I am not sure if anybody out there can help. >> >> It’s a long story, which I shall keep short. I have a brand new SC46 engine which I damaged the carburettor barrel on, and possibly the high and low end mixture screws. I have replaced the carburettor barrel, and am using a new high end mixture screw (actually from an older SC carburettor, but it looks identical) and a new low end screw. Try as I might I cannot get any settings that will allow the engine to run at any setting for any length of time. I have read articles and tried various starting points; the first port of call has been to try to get the high end mixture set. But it does not seem to stay stable enough for any length of time. I have tried the RCM&E advised method of setting the low end screw as advised in a recent magazine (needle in carburettor barrel to obtain a small opening and then blow down the fuel inlet while turning the low end mixture until air starts to flow), but I am not sure that my setting is correct.>> >> Does anybody have the factory settings for these carburettors, so that at least I know I am in the right ball park?>> >> Or any other ideas? My fuel is 5 months old, my glow plug as fitted new when I got the engine 5 months ago, through which I have run about 4 tanks of fuel when it was running OK before I damaged the carburettor.>> >> Thanks in anticipation.>> >> Tim Cheal>> Quote Link to comment Share on other sites More sharing options...
Kelly Posted January 1, 2010 Share Posted January 1, 2010 This thread may help http://www.rcgroups.com/forums/showthread.php?t=205602 Quote Link to comment Share on other sites More sharing options...
Tim Cheal Posted January 1, 2010 Author Share Posted January 1, 2010 Thanks you for the direction. That is what I will try tomorrow! Thanks again Tim Quote Link to comment Share on other sites More sharing options...
David Davis Posted January 2, 2010 Share Posted January 2, 2010 In my experience, if an engine doesn't fire, assuming it's mechanically sound with a good glow plug of the appropriate heat range, and a correct sized propeller, then it's probably flooded. If it is flooded, clear the excess fuel by disconnecting the fuel pipe and removing the glowplug, open the throttle and turn the engine over with the starter motor for ten or fifteen seconds. All of the excess fuel should now be expelled through carb, plug hole and exhaust port. To be absolutely sure you've cleared it, assuming the engine is mounted in a model, pick it up, turn it onto its starboard side and turn the propeller a few times, then tilt the model upwards. Any fuel that was lurking in the silencer will now run out of the tailpipe. I'll concede that this is a bit more difficult if the engine is mounted on a bench. Having reached this stage, blow the excess fuel from the glow plug element and check that it still glows. All good? Refit the glow pug and set the throttle to about 1/8th open. Attach the glow clip and turn the motor over having set the main needle and the slow-running needle as per the post mentioned by Tim. You should see fuel being sucked into the carburettor and the engine should start. You are using transparent fuel tubing aren't you? Having got the engine to start and run at these settings, leave it alone. Let me repeat that just to make things crystal clear. LEAVE IT ALONE! The classic beginner's mistake having got the engine to run at this setting is to whack open the throttle or worse still to open and close the throttle very rapidly and wonder why the engine stops. Leave it alone to build up to a working temperature. Having left it alone for 20-30 seconds, slowly advance the throttle. If the engine stops more or less immediately it's probably too weak so open the main needle by 1/4 turn and try again. Are you able to advance the throttle all the way to wide open? Is the engine running unevenly with lots of smoke? It's too rich, screw in the main needle until you get maximum rpm then unscrew it 1/8 to 1/4 turn as recommened in Tim's thread. Having got it to run at high and medium settings, turn your attention to the low-speed needle applying the same principles as you did with the high speed running. In a nutshell: get it up to temperature, adjust high speed, then adjust low speed. At the end of the process you should be able to whack the throttle open from idle to full power and from idle to stop. If it's any consolation it took me over an hour to get a recently purchased Merco 61 to run for the first time last week and I've been around engines for years. It runs well now that I've found the settings. I use the Firepower FF7 plugs in everything these days, Quote Link to comment Share on other sites More sharing options...
Tony Cooper Posted January 2, 2010 Share Posted January 2, 2010 I have an SC46 with remote needle valve, It runs very erratic if the tank is not pressure fed from the exhaust, the needle is approx 3 turns from closed, htis is where I stsrt from when ever I have to take the needle out (removing the cowl). hope that this is of help. Quote Link to comment Share on other sites More sharing options...
Tim Cheal Posted January 2, 2010 Author Share Posted January 2, 2010 Thanks Guys. The engine is in a Seagull Booomerang, with pressurised tank and clear tubing. Your advice is greatly appreciated. The snow in Manchester has precluded me running it today, so I will try tomorrow. Thanks again for all your advice, I will let you know how I get on. Regards Tim. Quote Link to comment Share on other sites More sharing options...
Myron Beaumont Posted January 2, 2010 Share Posted January 2, 2010 Tim When you say "won't run for any length of time" unquote -Just how long & how consistently ?. It might not be the engine at all . An outside influence I think ? Loads of possibilities as explained . Quote Link to comment Share on other sites More sharing options...
Tim Cheal Posted January 3, 2010 Author Share Posted January 3, 2010 I have just got in from tinkering for an hour or so. Its -1deg C, so not sure if that has any effect. If I give a sitrep then ask some questions. Thanks to all your help I am much farther forward. The engine is starting much easier, and I can now 'rev it up and down over a small range fairly quickly without it stuttering. However, if I set it to full throttle (or nearly full throttle) after about 10 seconds the engine simply dies. I would guess that it goes lean before it simply runs down. (I say that because of the pitch of the revs (very high) and the fact that to start it next time I need to get fuel in the carb by putting my finger over the carb inlet... does that make sense?) I have no control over this with the main needle. Could I ask a couple of questions. I notice that the fuel pipe from the exhaust to the tank gets full of 'gung'. Is that normal? Should I have a filter in the line? It is - 1 deg C. I managed to get the engine 'hot' (at least too hot too touch) but will the temperature prevent top end running? Should I buy a new glow plug and fuel just in case? Any recommendations on either count? Regards TimEdited By Tim Cheal on 03/01/2010 17:23:59 Quote Link to comment Share on other sites More sharing options...
Tony Cooper Posted January 3, 2010 Share Posted January 3, 2010 How old is the fuel? it tends to be hydroscopic, but I do not know how old it can be ,I do know that even with the plastic container sealed it goes absolutely useless after 15 years or so Quote Link to comment Share on other sites More sharing options...
Tim Cheal Posted January 3, 2010 Author Share Posted January 3, 2010 The fuel is 5 months old (or at least I bought it 5 months ago!). Regards Tim Quote Link to comment Share on other sites More sharing options...
David Gilder Posted January 3, 2010 Share Posted January 3, 2010 Tim, Not wishing to "teach grandma to suck eggs" but I had a similar problem with an OS 40LA that cut out when advanced to high throttle but ran fine at low end throttle.. This may have no bearing on your engine but I traced my fault to the fuel line having a pinprick hole near to the needle valve. Not a problem with slow fuel flow but it opened up when throttle advanced and fuel flow increased, meaning it sucked air into the fuel line and effectively starved the carb of fuel. Easily remidied with a new fuel line and 2 mins of time.... Probably not your engines problem but always worth a new set of fuel lines to be sure!! Where in Manchester are you? I'm in Glossop!! Dave. Quote Link to comment Share on other sites More sharing options...
Tim Cheal Posted January 4, 2010 Author Share Posted January 4, 2010 Thanks David, Definately worth a change fo fuel lines to see. I am in Wilmslow, and have joined the flying club at Total Fitness on the A34 bypass. Thanks for the help. Regards Tim Quote Link to comment Share on other sites More sharing options...
Tim Cheal Posted April 11, 2010 Author Share Posted April 11, 2010 If anybody is interested I tried everything. The guys at the club could not get a consistent setting either so I eventually took the engine back to the shop, who sent it to SC. SC could not get it to run properly either, they have replaced the engine and the new one runs as sweet as anything!! Regards Tim Quote Link to comment Share on other sites More sharing options...
Stephen Grigg Posted April 11, 2010 Share Posted April 11, 2010 Thats a pleasing end to your problem Tim,but probably the fact the experts couldnt figure it out you know it wasnt you,well done mate Quote Link to comment Share on other sites More sharing options...
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