Derek Broadhurst Posted February 24 Share Posted February 24 I bought this engine in used condition. I couldn't get it working as per start up instructions in the manual... Think it's worth mentioning I have been in this hobby for over 30 years. The only way it would start was by backing up the main needle from one turn to four turn's out. It ran but rpms were only 5000.,. I sent it to MMM, who knew the engine . He replaced the carb and sent a video of it running great. I I eventually got it on my test bench for a much awaited start up. It was impossible to start in the one turn out on the main needle as before! No air therefore fuel can pass through the needle valve at this setting. Once again it took four turns out for fuel to enter the carb . Engine hits 6000 rpm but it's erratic and cut's out.. I'll be in contact with Morris mini motor as this can't be right. Meanwhile if anyone can help please post. Thanks. Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 25 Share Posted February 25 Hi Derek, and welcome to the forum. I'm not familiar with the carburettor on this engine but it has two adjustments if the manual on the internet is correct for the carb fitted. If you don't lean the high end needle properly i.e. using 4 turns when the starting suggestion is 1 1/4 to 1 1/2, then it will run very rich at high throttle openings causing misfiring and low RPMs. Normal procedure is to set the high end and then adjust the low end needle for idle, which sounds to me to be either blocked or too far in. This may need to be repeated once or twice to balance both settings. Once it's set correctly, the starting behaviour should be fine. Neither of the needle settings will affect air flow through the carb, by the way. You've not said how long ago it was at MMM but another possibility, assuming your carburettor incorporates a diaphragm fuel pump, is age/ethanol induced hardening of the diaphragm or other rubber parts. Quote Link to comment Share on other sites More sharing options...
Brian Cooper Posted February 25 Share Posted February 25 Stale petrol. 1 Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted February 25 Share Posted February 25 6 hours ago, Brian Cooper said: Stale petrol. I used to think that, 'but' I got my Saito FG-30 out after a year with 1/2litre of my old 5% petrol mix and although I had to open the main screw 1/4 of a turn it ran perfectly, I re mixed another litre and flew it another 2 days without touching the carb even though it was a new mix. Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 25 Share Posted February 25 First and foremost it is impossible to tune an engine by counting turns on a needle. It simply cannot be done that way so dont worry about the number of turns and just tune the engine using the standard procedure Martin has outlined until it runs correctly. The engine should also have been delivered back to you from MMM with the needles in their last running position. I would have left them alone and just fired up the engine, there was no need to move them. The type of carb used on that engine will not allow you to blow through it like a glow carb so i wouldnt not be concerned about that. It is also pumped so you may find you get no/low fuel flow while the pump is dry. Seeing no fuel flow you open the needle, the pump primes, and now you are slobbering rich as Martin describes. This should be easily identified by puffs of black smoke from the exhausts. A petrol engine this size will use a microscopic amount of fuel at idle so do not be surprised if the thing seems to be completely closed off. Stale fuel cannot be ruled out (unless you know its fresh), i would also be looking at the ignition side too and make sure all 3 sparks are in their correct places, ignition battery up to spec etc. My gut feeling though is the engine is simply mistuned, and its probable there are some procedural issues on your side leading to this poor state of tune. Petrol engines do not respond the same as glow and handle differently. Using glow procedures and knowledge when dealing with a petrol engine can be problematic. If you are able to shoot a video of the engine running and post it here it will be much easier to diagnose running and procedural issues. 1 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 25 Author Share Posted February 25 Thanks for your response everyone. MMM. REPLACED the carb and ran it in it's setting. 1/1/4 out on the main screw.sent it back to me .No matter where I set the throttle as per manual no fuel would pump into the carb... I have ran petrol engines for many years but this is the first multiple cylinder engine. New fuel is being used. As mentioned anything less than four turns out on the main needle and it cuts out . What is going wrong? I'll try and post a video at some point.. Thanks Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted February 25 Share Posted February 25 Derek, without being condescending have you checked the tank, we had problems with my mates moki 215cc, would only run on partial choke, he swore the plumbing was fine, so we took the engine out and Kingfisher serviced the carb and ran the engine. Back in the model same again, problem was feed line from the tank got kinked as the tank was pushed into location. 1 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 25 Author Share Posted February 25 Many thanks for your help Frank. I have used the same tank to run up all the petrol engines pre installation to a airframe . I did suspect air in the line through vibration but sorted it. I managed to get back to Satio today and made some progress... I returned all the settings as I received it from MMM. Tried to start and nothing happened. Main needle 1 1/2 and slow 8 turns out throttle 1/4 open. Only way it would fire up is main needle 2 turns out and l the low needle backing out to 9.5 turns out. Tick over is now decent and revs are in the 8 k.. I feel I can get more RPMS but it'll wait until tomorrow.. I have posted a video. Many thanks again for everyone's input. I'm always ready to listen to other fliers input.👍🛩️ VID_20240225_165131780.mp4 VID_20240225_165131780.mp4 1 Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 25 Share Posted February 25 (edited) Yikes that idle is rough as a badgers backside. Its only running on 1-2 cylinders at idle with the 3rd (likely no2 cylinder) only popping in and out from time to time. While this is partly due to the less than stellar induction and conrod geometry induced timing problems it should not be that lumpy. I recently rebuilt a saito 170r3 glow and it was pretty smooth running in its stock form and better still after i modded the intake. Even with a slight rich misfire on no2 cylinder the engine ran very smoothly so i would suggest this is running very rich still. You mention you keep adjusting the various needles but what procedure are you using to do it? The numbers of turns mean nothing (other than perhaps to signify a problem if they substantially differ from the saito specs) and the engine cannot be tuned this way. It can only be tuned while running and it should take only 2-3 minutes to set both needles if standard procedures are used. Edited February 25 by Jon - Laser Engines Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 25 Author Share Posted February 25 Hi Jon I can't compete with your knowledge of these engines. As mentioned it's a MMM engine with the mods that they specify for the motor. Any changes in the settings are done with the engine running, and it seemed better on the RPM. I'll be spending more time with it tomorrow. I'll also ring Morris for a chat. Hopefully I'll be on the money after that. Cheers Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 26 Share Posted February 26 If its been MMM modified it will may have the intake 'upgrade'. I say it like that as i took a look at this upgrade part with the 170 i worked on and the design concept is fundamentally flawed. It is still an improvement on the saito effort, but the holes into the crankcase are utterly pointless. The claim is they improve bottom end lubrication, but this isnt true as there is nothing forcing fuel forward into the case. Shoving fuel into the crankcase is daft concept anyway as fuel in the crankcase will not aid lubrication. Pure oil getting past the rings will lubricate better than oil diluted with a boatload of methanol, to say nothing of the corrosion issues. There will also be loss of differential pressure during the induction stroke due to increased volume in the induction system and this will reduce fuel draw. There are other issues too. Multiple direction changes for the incoming charge, used oil being recycled into the induction charge, no venting of residue from the crankcase... I was not at all impressed so made a much simpler job which worked very nicely. Although, bit of a lightbulb moment. If it has the MMM intake upgrade you need to make sure the crankcase vent is blocked. Failure to do so will result in a massive intake leak and all sorts of tuning and fuel flow problems. This might explain some of your problems if it has the mod and your breather is open. You will need to ask MMM about the spec of the engine to work out what it is you actually have. If it is in stock saito form the breather needs to be open. 1 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 26 Author Share Posted February 26 Hi Jon thanks for the information. Crank breather is plugged up. I'll be on it later today and give MMM a bell. I have to get this right. Quote Link to comment Share on other sites More sharing options...
Paul De Tourtoulon Posted February 26 Share Posted February 26 2 hours ago, Jon - Laser Engines said: as fuel in the crankcase will not aid lubrication. Pure oil getting past the rings will lubricate better than oil diluted with a boatload of methanol, to say nothing of the corrosion issues. Interesting, after 50+years, of rc planes I hadn't even thought about that. Quote Link to comment Share on other sites More sharing options...
Engine Doctor Posted February 26 Share Posted February 26 The Moki 50cc 4 stroke i had used a walbro carb . As you know they need a pulsed air pressure to operate the pump. I assume the Saito uses a similar type of carb ? If I remember correctly it still had a crankcase vent nipple to expell excess oil but this was reduced in size so that there was still enough pulse from crankcase pressure to operate the pump. I dont know how the Saito c/case generates much of a pulse as the pistons movement probably canceles out the pulse. I have found that fully blocking the carb with a finger while turning the engine with a fully open throttle until fuel reaches the carb then a couple more turns to prime engine makes for easy starting Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 26 Author Share Posted February 26 Hi Engine Doc. Thanks for your help, Yes the Satio carb has a pump incorporated all be it a weak one. I used some back pressure in the tank to push fuel to the carb(access is restricted)but only after opening the needle another turn otherwise it felt like I had a closed needle. I have spoken to Morris today and feel I'm closer to having the issues of rpms sorted. Cheers Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 28 Author Share Posted February 28 Hi after a few efforts to sort the problem out though we got somewhere after blowing out the carb. Needle valve was set back to recommend setting 1.5 out . And air could be heard to go into the carb . Unfortunately I couldn't get the 6500 rpms out of this engine .. Morris mini motors has asked me to send it back, hopefully I'll have good news soon. Quote Link to comment Share on other sites More sharing options...
Jon H Posted February 29 Share Posted February 29 (edited) How many RPM did you get? and on which prop? I know i have made mention of this a number of times during this thread but you cannot tune/setup/operate engines by fixed numbers. This many turns on a needle, so many rpm, this cylinder head temperature etc. Engines a more nuanced and at our end of the scale they vary massively day to day. As an example, if i say to a customer that one of the Laser engines should do X RPM of Y propeller, i know that anything +- 200rpm on that figure is perfectly normal. Unfortunately, trying to explain to customer A that his engine is fine at 8400rpm despite customer B reporting on a forum that his example of the same engine does 8800rpm on the same prop is very difficult and customer A feels he has a dud engine. But is it the same prop? Different brands will run at different speeds despite the same DxP. In fact i have two seemingly identical APC 16x8's here and they run 500rpm apart when tested back to back on the same engine. It seems APC changed the design somewhere along the line as customers have reported similar issues to me and even sent me their props to test. Also where does customer B fly? Is he in a hotter climate, colder, higher altitude etc. There's a customer in Austria who is half way up a mountain and his engines rev like crazy as the air in thinner. Power is down for the same reason, despite the higher rpm. Day to day variation can easily be 200rpm even here in the UK so the engine might have been fine. Clearly if you were 1000rpm down something is not right. Without observing your procedures for running the engine and having all the data its hard to say what the problem is. However i fear that inadequate adherence to tuning procedures, unfamiliarity with the engine, unnecessary fiddling and dismantling of the carb (in my view as blowing air through a pumped carb can ruin it), and an over reliance on numbers is likely to be the root cause of your problems. If Morris finds a dead otter in the carb or other problem then fine, i will gladly eat my words but i do not think he will find much. If there is a dead otter in the carb why is it there? Where did it come from? Always wash out your fuel system and check for otters (or more likely, grass and fluff). Edited February 29 by Jon - Laser Engines 1 Quote Link to comment Share on other sites More sharing options...
Frank Skilbeck Posted February 29 Share Posted February 29 1 hour ago, Jon - Laser Engines said: If Morris finds a dead otter in the carb or other problem then fine, i will gladly eat my words but i do not think he will find much. If there is a dead otter in the carb why is it there? Where did it come from? Always wash out your fuel system and check for otters (or more likely, grass and fluff). Reminds me, years ago we sold a test water treatment dual unit to a French oil company, they reported on test that one of the units performed much better than the other, I was sent to investigate, short story when they were rigging it up they left an open 4" hose on the ground, it had got a few handfuls of gravel in it, when they started it up the piping configuration sent all the gravel to one unit and blocked it's inlet................ Took about 30 mins to find out and "repair" still had a very nice lunch. 1 1 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 29 Author Share Posted February 29 Hi Jon.. after reading the in depth post I get where your coming from on the needle setting. I will give you some info hopefully setting the background 1/ I'm in the Lancashire area. Not the Andes LoL 2/ prop is a 18/8 wooden Airostar. 3/ top rpms are 5000 and erratic Needles set at factory values after I used the air line.. I felt the engine was ticking over better but it's woefully down on high end no matter what I do... The engine was sat for Four months after it came back from MMM with the NEW carb he did run it up and posted it back. Could the fuel have congealed in the pump or something in that time? I know I'm just trying to understand what happened. I have been in this hobby for 30 odd years tuned many a engine but this has got the better of me. I had a chat with Morris and he's asked for the engine so he can look at it.. so I'll post what he finds. Many thanks guys for your input... Quote Link to comment Share on other sites More sharing options...
Brian Cooper Posted February 29 Share Posted February 29 Just a thought - and trying to eliminate the obvious - is the ignition battery in good condition? If it is in poor health, it can seriously affect the performances of an engine, especially the top end RPM. Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 29 Author Share Posted February 29 Hi Brian many thanks for your help. Yes I have a healthy 2s lipo. Your right a below par battery especially on a multi cylinder will cause problems... I hope to have some good news shortly. 1 Quote Link to comment Share on other sites More sharing options...
Denis Watkins Posted February 29 Share Posted February 29 (edited) Oh Derek, please check that the 18x8 is not a Typo mistake, as it seems so being way overpropped. Edited February 29 by Denis Watkins 1 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 29 Author Share Posted February 29 Hi Dennis it's correct for the engine both in the manual and MMM recommendations... Quote Link to comment Share on other sites More sharing options...
Martin Harris - Moderator Posted February 29 Share Posted February 29 Denis might have a point... 1 Quote Link to comment Share on other sites More sharing options...
Derek Broadhurst Posted February 29 Author Share Posted February 29 I had a 17/6 on initially I forgot to mention that,also MMM asked me to try a 18/ 8.. the rpms are massively out and erratic no matter what was on it . Let's see what happens when MMM gets to work on it... Cheers. Quote Link to comment Share on other sites More sharing options...
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