Bruce Collinson Posted September 4, 2019 Share Posted September 4, 2019 It would be misleading of me to claim expertise but it sounds like there’s a spark but no fuel. My two petrols, a Zenoah and a DLE, pulled fuel from miles back so the finger points at the carb and Chinese knock-off Walbros seem to be temperamental. We have a decent lawnmower man nearby who supplies service kits for Walbros and will fit them too. Just a thought. BTC Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 4, 2019 Author Share Posted September 4, 2019 Thanks cymaz and Bruce. Priming by hand I could see fuel pulsing in the line, so it looks as if there is some draw. I will try injecting some fuel into the intake and see if anything kicks off, I would have done that already but being a rear induction motor it’s a bit awkward. Possible diaphragm issues noted, it is a brand new motor and I haven’t touched anything out of the box, but as so often happens it has been lying around for a year or so before I have tried to use it so there could be an issue there. Hopefully I won’t need a Walbro conversion but you never know. Same old story isn’t it though, you take on something quick and simple for some extra flying and it turns into a major diversion you can do without! Quote Link to comment Share on other sites More sharing options...
Rich too Posted September 4, 2019 Share Posted September 4, 2019 Looks good Colin. My zenoah 23 is a nightmare to start and likes a squirt of fuel into the carb. Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted September 4, 2019 Share Posted September 4, 2019 Yep, give it a squirt. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 4, 2019 Author Share Posted September 4, 2019 Thank Rich and John. Will do! Quote Link to comment Share on other sites More sharing options...
Doug Moss Posted September 5, 2019 Share Posted September 5, 2019 Try disconnecting the tacho? Quote Link to comment Share on other sites More sharing options...
Ian Denny Posted September 5, 2019 Share Posted September 5, 2019 I had exactly the same symptoms with a brand new OS GT33 at the weekend. Checked fuel was being drawn from the fuel tank to the carb. Took the spark plug out and it was wet, but as clean as a new plug. The engine was inverted and fuel even dripped out of the plug hole in the cylinder, so I knew the problem wasn't fuel related. I then disconnected the opto kill switch and manual toggle switches between the ignition unit and LiFE ignition battery, and connected the battery directly to the ignition unit. Fired up after 2 flicks ! Traced the problem to the manual toggle switch for isolating the ignition. One of the pins in the radio plug was not making contact. Replaced the radio plug and everything now works. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 5, 2019 Author Share Posted September 5, 2019 Doug and Moss, thank you both. The tacho suggestion is interesting, sounds like there is some experience of this happening? I will include that as I work through the options. I don’t have a manual switch in the ignition circuit on the plane, I am using one of the auxiliary channels through a toggle switch on the tx and that all appears to be doing what it should. I am working today and won’t get time to have another look until tomorrow. It did occur to me though to see what happens if I connect the ignition directly, to confirm or eliminate where the problem might lie. Incidentally, the RCGF technical literature says that the carburetter is a Walbro, I need to look at it more closely. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 9, 2019 Author Share Posted September 9, 2019 I think the opinions on the diaphragm being dried out might be correct. The new plug arrived from Morris Mini Motors so I fitted it but I don”t think there’s wrong with the old one. I spent a lot of time spinning it with the starter, squirting fuel into the intake and also opened both high and low needles by a turn. Eventually I got it going and worked the needles back to factory settings. There’s a learning curve here for me. Hopefully video will show on the next posting! Edited By Colin Leighfield on 09/09/2019 21:27:53 Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 9, 2019 Author Share Posted September 9, 2019 Edited By Colin Leighfield on 09/09/2019 21:34:54 Quote Link to comment Share on other sites More sharing options...
Stuphedd Posted September 9, 2019 Share Posted September 9, 2019 with all this talk of Stiks and Sticks , where does my Extra Stick fit in ??? it is a bitsa , I saw the wings at Weston , and built the rest eyeing up photos ans scaling then to suit , and its alum stringered as is my wont . cheers cheers Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted September 9, 2019 Author Share Posted September 9, 2019 Mine is actually an Ultra STICK. I got confused and spelled it as STIK when I opened the thread and don’t know how to correct it! Either way, they all seem to work well enough! Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted October 9, 2019 Author Share Posted October 9, 2019 So often when you squeeze a “quick project” in between others it takes on a life of its own and this is certainly the case here. Other things going on and weather issues have put off the opportunity for the first flight, I had got today clear but looking at variable weather and strong gusting winds this morning it was seeming like another no-go. In the end I went anyway thinking this model should cope with a bit of wind and you can’t put things off for ever. I have learned how to get the engine going quickly now and having run a couple of tanks through in the back garden at fast tick-over it feels like it should. I changed the 12”x6” prop for a 13”x6” and off I went. At the airfield it was bright and sunny, the flying conditions weren’t great though because of the gusting wind, described by the two pals who were there. However it was flyable, good enough. I did the range check, perfect. The engine started immediately. Control checks looked ok but when I began to open the throttle there was massive interference induced loss of control, surfaces were moving all over the place and the throttle wouldn’t close. Fortunately the ignition control did still work and I was able to kill the engine. I re-started the engine twice but it was obvious there would be no flying today. There is serious ignition interference with the radio. Now I need to identify the best way to prevent this. Not a problem I have ever had to deal with before and this is my first experience with a petrol engine. Not a good start. Any easy solutions anyone? Quote Link to comment Share on other sites More sharing options...
cymaz Posted October 9, 2019 Share Posted October 9, 2019 Obvious question first.....35mhz or 2.4 ? Try and reduce interference by having some space between the Rx and CDI circuits, not easy to do in some models Keep the CDI Box well away from the Rx. Using some ferrite rings might help on the switch and battery wires Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted October 9, 2019 Share Posted October 9, 2019 What Cymas says, how's the pipe fitted, any metal to metal noise there ? Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted October 9, 2019 Author Share Posted October 9, 2019 Thank you Cymaz and John, much appreciated. The CDI box is buried up front under the fuel tank and is about 9” away from the rx, can’t get it much further than that. The tuned pipe extension is connected to the silencer with a flexible extension, although the tuned pipe itself is attached to two steel brackets under the fuselage with two jubilee clips. The only concern I had was in finding space for the CDI box and squeezing it into the space below the tank. I had hoped to “float” it inside foam but all I could do was apply a thin layer of foam plastic about 3mm thick top and bottom, itnis a tight fit and I wondered if there could be a vibration issue there. Can’t think of anywhere else to put it though. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted October 9, 2019 Author Share Posted October 9, 2019 Sorry Cymaz, I forgot to say it’s on 2.4. Where do I obtain ferrite rings? Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 9, 2019 Share Posted October 9, 2019 First of all Colin, check the HT lead for breaks in the braid or a poor connection to the plug cap and that the plug cap is actually on tight. Could the plug have had a knock? Might be worth just trying a new plug anyway, they have been known to cause interference when they go bad. Can you get another ignition unit to try? None of the petrol engines that I had caused interference unless something was broken, both times it was a loose plug cap. Are you using a separate battery for the ignition? Quote Link to comment Share on other sites More sharing options...
john stones 1 - Moderator Posted October 9, 2019 Share Posted October 9, 2019 Sounds a good distance away, you got any extension leads in there ? worth checking and swapping those. Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted October 9, 2019 Author Share Posted October 9, 2019 Hi Bob. The engine is all new and the braided lead looks perfect, the plug cap also seems to be on ok, it’s a very tight fit. When I was having trouble starting the engine initially I bought and fitted a new plug, so it should be ok but I could always put the original back in for comparison. I don’t have a spare CDI unit, but it came with the engine and is also new. The ignition is powered by a separate 4.8V battery. Cymaz, thanks again. There are extension leads in there. Clearly chaps I need to have a systematic look all the way through, that’s the next step. Quote Link to comment Share on other sites More sharing options...
Bruce Collinson Posted October 10, 2019 Share Posted October 10, 2019 You've given a very accurate description of what happened to one of mine; servos going absolutely haywire. The cap isn't on all the way. My second, a DLE 20, needed careful application of a plastic speedclamp to get the cap to snap onto the plug. Yes sounds brutal, I don't have especially strong hands, worked for me. You mentioned earlier that the cap was a bu**er to get off. Res ipsa loquitur. I assume what happens is that the spark will happily jump the gap with enough welly left to spark the plug but creates all sorts of interference, sending you looking up all the blind alleys for faulty components and duff radio installation. One of several reasons why my experiments with petrolly engines were abbreviated; noise, temperamental jets on knocked-off Chinese Walbros being the principal ones. DLE out (sold), Saito 125 in. Of course the others may be right but in a little used engine, my fix is no-cost. best of luck, report back. BTC Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted October 10, 2019 Share Posted October 10, 2019 BTC , spot on Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted October 10, 2019 Author Share Posted October 10, 2019 Hi Bruce. There is a fair chance you are right I think, when I get home later I will have another look. When I had the original starting trouble and changed the plug on the off-chance I couldn’t believe how hard it was to get the plug cap off. Afterwards I also couldn’t believe how hard it was to get it back on and I can well believe that it isn’t all the way down even now. I will resist the temptation to bash it with the sledge-hammer and consider a more subtle technique such as the one you chose. I will report back. Quote Link to comment Share on other sites More sharing options...
Bob Cotsford Posted October 10, 2019 Share Posted October 10, 2019 The 1/4" twist lock plug cap on my Evolution was deceptive, sometimes I thought that I'd twisted it far enough to lock but once the engine fired the cap rotated back again. It should have a definite detent in the locked position and getting it twisted past the detent took more force than you'd think on such a little plug. Edited By Bob Cotsford on 10/10/2019 21:48:57 Quote Link to comment Share on other sites More sharing options...
Colin Leighfield Posted October 10, 2019 Author Share Posted October 10, 2019 Hi again Bob. This one is a straight push fit but so stiff you get no sense of location or positive detent. I’m getting to have a go at it tomorrow. Quote Link to comment Share on other sites More sharing options...
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