David Coney Posted October 8, 2023 Share Posted October 8, 2023 A nephew of mine has given me a model aircraft complete with model diesel engine, but I can’t get it to run continuously, it only seems to run on what I prime it with through the ports. Is there anybody out there who might be familiar with this specific type of engine who could give some advice ? I know the engine has run in the recent past satisfactorily. When it came to me this time it was locked solid so I had to dismantle and ease everything off. So maybe when I put it back together I’ve made some error. The make is DC Ltd., (Davies-Charlton, the piston diameter is approx. 1 cm and the cylinder is an anodised red colour. In the cylinder liner there are ports at two levels, three ports at each level, displaced from one another - how critical is the positioning of the liner, in a radial direction ? The needle valve assembly/carburettor has two holes in it, should these be in a vertical position or horizontal ? Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 8, 2023 Share Posted October 8, 2023 If you can get it to start and run you already have half the battle won. Most likely it is a fuel feed issue caused by either the needle being blocked, set too lean, or the tank fuel level being too low. Aim to have the fuel level and needle valve level either the same or the fuel a smidge lower. If its too high the engine will flood. Many diesels need a good crank of compression once they have fired up and you only have a second or two to do it, so this may be a problem as well. Quote Link to comment Share on other sites More sharing options...
J D 8 Posted October 8, 2023 Share Posted October 8, 2023 Needle valve with two holes should be set horizontal. 1 Quote Link to comment Share on other sites More sharing options...
David Coney Posted October 9, 2023 Share Posted October 9, 2023 Thanks for your answers guys and the position the cylinder liner should be in , radially ? As a new ‘poster’ I realise now I should have started a new topic, sorry about that Quote Link to comment Share on other sites More sharing options...
J D 8 Posted October 9, 2023 Share Posted October 9, 2023 Hi David, It's best to carry on in same post as Merlin info ends up all in the same place and can be found if "merlin" put in the search bar on start page. I have a Merlin which has not been in a aircraft for years but gets run on the bench now and then just because. The liner has 3 inlet and 3 exhaust ports, there are only two ports in the casing so mine is set with fully open exhaust port on the right o/s and divided one on the left. Do not know for sure if this is right but mine is happy like that. John. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted October 9, 2023 Share Posted October 9, 2023 Hi David. Positioning the cylinder on DC engines once run in can cause issues if the case and liner are not marked prior to stripping down. Just try fitting the head on finger tight and gently turn engine over. If any tight spot can be felt turn cylinder slightly until its smooth and bouncy then tighten head properly. The engine you have is a Sabre ( red cyl head) of 1.5cc capacity. Was the gasket around the backplate ok ? And the fibre washer on the cylinder liner should fit on the top of fllange there shouod also be a paper gasket that fits over the cylinder and seals the cylnder to crankcase . Open NV 2 1/2 turns as a starting point. Good luck and enjoy. Quote Link to comment Share on other sites More sharing options...
Fuzzy-Felt Bloke Posted October 16, 2023 Author Share Posted October 16, 2023 Bit of an update. Engine has now been soaking for a week in fresh diesel fuel. Tried an 11" propeller on it and irs not moving at all. I will leave it for another week to see what happens. I would like to save the rest of the engine, is there a way to dismantle with piston seized in liner. The fines should unscrew, as its just a push fit on? Any advice? Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted October 16, 2023 Share Posted October 16, 2023 I assume you mean the finned cylinder head/cylinder liner sleeve then in theory, as far as I recall yes, but refer to my first post as there’s a strong possibility that it might try to twist the piston and con rod due to age related seizure between the head and the liner. Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 17, 2023 Share Posted October 17, 2023 12 hours ago, Fuzzy-Felt Bloke said: I would like to save the rest of the engine Dont admit defeat too early. My Dad's AM10 was swimming for goodness knows how long before it came free. If you want you could sent it to me and i can chuck it in the ultrasonic cleaner here at work. The fluid we use teaches castor a lesson with no problems. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted October 17, 2023 Share Posted October 17, 2023 Hi fuzzfelt- bloke. As Jon says dont give up. Try this.Take out from fuel ,drain and dry off then heat with a hot air gun gently building the heat until its too hot to touch .do this outdoors just incase any oil ignites. Its never done it with me but just in case. Leave the prop on while doing this to provide a lever to turn engine over when heated; provided its not a vintage nylon type as that is likely to melt . Concentrate most of the heat on the cylinderhead. Is shoukd be smoking a bit when hot enough . Whit a pair of stout gloves gently try turning the prop back and forth and apply some oil into the exhaust and air intake and keep rocking until it will turn over . Ive just freed up two MVVS diesels for a club member after they sat in a loft for over 20 years. It took about two hours each to free them but both are now running fine. Heat always wins if its gummed. Of course in the unlikely event that its mechanically siezed while running then heat is unlikely to help free it . Dont try undoing fins until it turns over . As Martin says you could eadily twist and snap the conrod. 3 Quote Link to comment Share on other sites More sharing options...
GaryW Posted October 17, 2023 Share Posted October 17, 2023 (edited) Heres one of the MVVS Diesels @Engine Doctor is talking about that he freed up and revived for me for my 7.5 pg gliders and i will concur that they run great again after 20+ years and it was good to see the diesel powered glider in the air again on sunday after not being flown for so long Edited October 17, 2023 by GaryWebb Quote Link to comment Share on other sites More sharing options...
Fuzzy-Felt Bloke Posted October 28, 2023 Author Share Posted October 28, 2023 Hi guys. I've managed to free up the engine and take it apart. Just needs a clean up, reassemble and test run. 2 Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 28, 2023 Share Posted October 28, 2023 nice one. I need to strip my DC sabre to sort out a sticking contrapiston. Its fine to get the thing going but it starts to get overcompressed as it warms up and it wont back off. I will sort it one day! Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted October 29, 2023 Share Posted October 29, 2023 Come on Jon 5 min job. Quote Link to comment Share on other sites More sharing options...
Jon H Posted October 29, 2023 Share Posted October 29, 2023 4 hours ago, Engine Doctor said: Come on Jon 5 min job. sadly there are plenty of longer jobs ahead of it! Quote Link to comment Share on other sites More sharing options...
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