Tony Patman Posted March 22, 2007 Share Posted March 22, 2007 This is a bit of an epic, but I couldn't find an engine thread for novices yet, so I thought I'd start one and hopefully get some tips at the same time.Right, so I lovingly crafted a sturdy test stand from scrap wood (design available from me if anyone is interested), screwed the engine in place, balanced the propeller, mounted the tank less than 1/2" below the carb., dribbled some oil into the crankcase, tubed it all up, choked some (5% nitro) fuel into the engine and flipped it a few times to distribute it, set the throttle to 1/4, opened the main needle 5 turns as recommended in the instructions, attached the glow clip and then spent the best part of an hour flipping and fiddling until I was ready to throw the whole lot out of the cellar window into the garden.Then I figured out that the glow clip cell had discharged, so I charged it up and, after about 5 minutes more of flipping, the engine spluttered into smoky life.Great. I managed to get through a tankful of fuel; but the engine would stop as soon as I removed the glow clip. Might it be that the mixture was so rich that it immediately puts the fire out?The model is going to be a pusher, but the plan stipulates that the fuel tank should still be mounted facing forwards; something to do with orientation in flight, perhaps? this will need quite long tubes, so I have cut them accordingly. Could it be that they are just too long for the engine's suck-n-blow to cope with? I've noticed that, a few flips after choking, the fuel drifts back down the tube from the engine and it needs choking again to bring it back (or a swift puff into the pressure tube from the muffler, but this is probably not recommended because it introduces moisture, right?).Anyway, the engine remains very difficult to get going. The best I've managed for the past couple of days is some spluttering, then air bubbles appear in the fuel line and it stops. I don't think the bubbles are coming from the tank, but from the engine end. Also, the glow clip only seems to last for about 10 minutes before it needs charging up again.Is it supposed to be this difficult? Maybe I'd better start saving up for some leccy gear.Tony. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 22, 2007 Share Posted March 22, 2007 A couple of things not right here TonyAir bubbles ! - are you SURE the piping inside the tank is all ok ? - has been known for a pinhole fault to develop internally in the tubing /pipingGlow power will depend on the size (capacity ) of the cell you are using to power it - if it is around 3000 m/a then this should last around an hour !! Typical glow plug consumes around 2.5 - 3 A. How long are the leads from the cell to the clip - and are they sound?Use ONLY an OS F type plug...in my experience they suit just about any 4T and I use nothing else in my SC motors -which incidentally all run excellently.5 turns out on the main needle seems a bit rich - a 90 SC 4T that I have is happiest at about 2 turns out.Check the idle screw and needle /jet are correctly set.There is nothing inherently wrong with these engines -they are fine budget motors :) IF you satisfy the following criteria then it MUST run ok1) CLEAN FRESH Fuel ( 5% is fine )2) Correctly fixed airtight sealed carb, with a clean properly set needle / needles.3) Compression4) Good plug5) FULL INTEGRITY of all fuel tubing and pipes. Certainly sounds like it was far too rich - and YES this excess fuel will put out the glow plug - especially slightly colder plugs. FS plugs are designed to hold the heat in a little longer to last through the extra cycles.Incidentally, some four strokes still like silencer pressure, and if you are using long tubing, then yours may well benefit. HTH Quote Link to comment Share on other sites More sharing options...
Tony Patman Posted March 23, 2007 Author Share Posted March 23, 2007 Timbo, thanks for your helpful response. The fuel is new and the plug is an OS for FSs.I'm not sure about the idle needle because I haven't got as far as fiddling with that yet; but maybe I'll screw it all in and then out a couple of turns to reset it.I'll also try leaning the main needle down to 2 turns as you suggest. I thought 5 was too much, but you know what they say: RTFM.The glow clip is in fact one of the integral jobs with the cell in the handle, so there are no leads.I'll also try substituting some different tubing. Incidentally, the muffler pressure to the tank is already connected.Tony. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 23, 2007 Share Posted March 23, 2007 Seems you had most of it covered then :)Please let us know how you get on.... Quote Link to comment Share on other sites More sharing options...
Tony Patman Posted March 23, 2007 Author Share Posted March 23, 2007 Will do. I'm going to have another crack this weekend. Quote Link to comment Share on other sites More sharing options...
penty Posted March 24, 2007 Share Posted March 24, 2007 wow, 5 turns seems a lot to me too.I've always started with about one and three quarters to two turns and taken it from there.(40-60 size 2 strokes, OS, Irvine and SC) Quote Link to comment Share on other sites More sharing options...
Tony Patman Posted March 28, 2007 Author Share Posted March 28, 2007 Well, now it seems that two turns at most is quite rich enough. It's still a bugger to get going, though.Tony. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 28, 2007 Share Posted March 28, 2007 It should not be difficult to start. perhaps it likes to be a bit wet before firing ? Is it a new engine - and have you checked the valve clearances are correct ? I always find that as long as I have a nice healthy glow on the plug, and fuel in the carby, my SCs fire up and run a treat. Quote Link to comment Share on other sites More sharing options...
Malcolm Fisher Posted March 28, 2007 Share Posted March 28, 2007 If your feed pipe is emptying back into the tank, the tank could be set too low.To get fuel back up the feed pipe, try putting a finger over the end of the muffler and turning the engine over. This should provide sufficient pressure to refill the feed pipe to the carb.Be careful not to overdo this if you are using an el;ectric starter - you could break the crank pin or bend the conrod if a hydraulic lock is generated. Quote Link to comment Share on other sites More sharing options...
Tony Patman Posted March 29, 2007 Author Share Posted March 29, 2007 Timbo - yes, it is new. No, I haven't checked the valve clearances because I don't have any feeler gauges and I would have hoped that they would have factory-set correctly. I think it is a bit sensitive to "wet", in both directions. I am sure that it gets flooded after a few flips: I have noticed that, if it starts, it generally does so quite soon after a "prime from dry". If it isn't going to start, I could stand there for half an hour flipping and it wouldn't go.Malcolm - I thought that too, about the tank, but it really is only about 3mm below the carb. Thanks for the tip about priming by blocking the muffler. No, I don't have an electric starter; but I was starting to consider getting one!This forum is proving so useful! Thanks, chaps. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 29, 2007 Share Posted March 29, 2007 Hi Tony, sounds like you are not having much fun with your SC, silly question but when you say the tank is 3mm below the carb, which bit of the tank are we talking about? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 30, 2007 Share Posted March 30, 2007 good point -I hope he refers to the centreline! Quote Link to comment Share on other sites More sharing options...
Tony Patman Posted March 30, 2007 Author Share Posted March 30, 2007 Hee hee, yes, fair question. I do mean the centreline, judged as the place where the main fuel line emerges. It's one of those Slec cuboid tanks. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 30, 2007 Share Posted March 30, 2007 OK Tony...I fear we are back to just double checking ALL the basics as mentioned earlier. I know u havent got a feeler guage, but just pop the rocker cover off, and see how the gaps look ( cold engine ). If they are way out, you should be able to notice...or indeed if they are not opening fully either. It is a slight possibility that the lock nuts have loosened.How is your "flipping" technique - it can make a difference :)Have you tried NOT using exhaust pressure...some like it that way. Quote Link to comment Share on other sites More sharing options...
Tony Patman Posted March 30, 2007 Author Share Posted March 30, 2007 Some more "wisdom" gleaned: don't try to run your engine in your cellar unless you have an industrial-scale extraction system. Despite my efforts to create a local extraction hood around the muffler using flexible tubing, plastic flowerpots and an old inner tube I found in a skip, I still half-gassed myself and had to go to lie down until all the carbon monoxide had seeped out of my body. Next time I'll go outside and annoy the neighbours with the noise instead... Quote Link to comment Share on other sites More sharing options...
Tony Patman Posted March 30, 2007 Author Share Posted March 30, 2007 I'll have a look at the valves over the weekend. I have been scared to remove the rocker cover in case I disturb perfectly good settings without the skill to reset them!My flipping technique is to move the prop. anticlockwise until I can feel the compression, then flick it over the compression with enough impetus to spin to the next one. I have read about another supposedly more reliable technique which involves "bouncing" off the compression, but I haven't managed to work out how to do this.I will try without the exhaust pressure. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 30, 2007 Share Posted March 30, 2007 Tony, when "flipping" the engine does the compression feel fairly strong, and if you move it slowly through compression (Glow disconnetced) does it still feel compressed? I know I am not making myself very clear here LOL. What I am getting at is I bought a brand new OS engine many years ago and it had a pinhole in the head, I know, it was an OS, well it still CAN happen LOL. Anyway it was a pig to spot because it would run kinda..... eventually I actually spotted a tiny bubble of oil/fuel between the fins during a running moment, it was replaced free of charge and no problems after that. Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 30, 2007 Share Posted March 30, 2007 PS Shouldn't laugh about your carbon monoxide moment because it could have ended more seriously, but the vision of all these makeshift noise deadening and gas extraction devices, aka plastic flowerpots and old innertubes was destined to failure really and did make me chuckle :) You aren't restricting the exhaust in any way are you? Quote Link to comment Share on other sites More sharing options...
Tony Patman Posted March 30, 2007 Author Share Posted March 30, 2007 Danny, I believe I know what you mean about compression. Well, to my inexperienced fingers it feels rather weak, but it is definitely there. Are you thinking that there might be a cylinder head leak or something? I'm sure that the plug is in tightly and with the little copper washer. Now that you raise the issue, though, there is a slight bit of bubbling from where the muffler is attached! Very slight, though.Re. CO: no, I know it could be serious, that's why I'm not doing it down there again. No, the exhaust is not blocked in any way. Maybe I'll take a pic of the extraction system and post it on here, just to give everyone a laugh. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 30, 2007 Share Posted March 30, 2007 The compression on 4 strokes never feels as much as you may be used to from 2 strokes. I never se the "bounce" starting technique - fast firm flick in the way you describe does it for me....except of course that I generally use a starter - and only revert to a hand start if it cuts on me at the strip :) Quote Link to comment Share on other sites More sharing options...
Danny Fenton Posted March 30, 2007 Share Posted March 30, 2007 You are probably right Timbo I am not familiar with four strokes at all LOL and I guess the compression would be lower with all those valves involved and and associated leaks than the two strokes I am more familiar with. Timbo even when using glow you still like to have your leccy motors don't you? ;) even if just for starting LOL Yes Tony a leak or a slight inclusion in the casting is exactly what I am thinking, not going to be easy to eliminate or prove. Anybody else got any thoughts??I am definitely interested in seeing the CO evacuation system installed in Chez Patman LOLOL Quote Link to comment Share on other sites More sharing options...
Aslan Posted March 30, 2007 Share Posted March 30, 2007 Tony,This might sound completely ridiculous,and I hope you won't be offended,but,do you have a pressure feed to the tank from the muffler? Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 30, 2007 Share Posted March 30, 2007 Asian..read the earlier postings in this thread :) Quote Link to comment Share on other sites More sharing options...
Aslan Posted March 30, 2007 Share Posted March 30, 2007 Hey.....I only asked.....Some times people only get a chance to briefly go through things and get a rough idea of whats goin' on, smart lad....O.K.I did apologise if it was already done....Jeez. Quote Link to comment Share on other sites More sharing options...
Tim Mackey Posted March 30, 2007 Share Posted March 30, 2007 Please dont get so ruffled asian...i only suggested you read the earlier sections in order to bring yourself up to speed with the thread. Quote Link to comment Share on other sites More sharing options...
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