DLE 20 Low end running issues

[Browny]

Hi all,

I've a DLE 20 in a Seagull Yak 54, from new it ran very well without any major issues other than being a bit of a pain to start and being loud.

I sorted the noise issues with a zenoah exhaust, but as of recently.

I've started experiencing problems as of late, a hunting issue at the low end followed by a problem where it wouldn't start at all unless on full throttle and was being whizzed over with a geared starter. I had noticed for a while, whilst filling on a T piece there was fuel leaking out of the carb somewhere. The vent line seems fine, fuel runs out of it when full.

I did remove the carb and do the usual checks on the butterfly and sanded all the gasket areas, reed cage and the sealing face of the carb body flat with 800grit on a flat surface

I put it all back together and it was fine, I took it for a flight, it fired rather easy. 15mins later and i came in for a landing (1/3rd of a tank left) making the turn for finals i throttle back below half throttle. And it started sounding as though it was bogging down. I tried to coax it back, but resulted in a deadstick and dropping into the rough un damaged.

For the life of me, changing plugs and fiddling with the idle screws i couldn't get it to idle or run under half stick.

I took the carb off again, stripped it all down and flushed it through with brake cleaner. Even the hole for the metering needle was flushed through.

I relapped the reed cage as i wasn't too happy with the seal around one edge. Cleaned it all out and re assembled and reset the needles as per the instructions. I then took the hall sensor away and checked for dirt and grease. There seamed to be some oil residue under the mounting plate, which i cleaned off, i've checked the spark and there seems to be a good spark.

Now the plane will run at idle, but the revs have started hunting up and down again. You can steady it down by richening the bottom end out, but it doesnt transition very well (which says to me its drawing air somewhere) If you lean it out, it picks up revs on idle. But it still persists in this rather annoying hunting situation.

I have noticed air bubbles in the fuel lines whilst running, which to me suggests it maybe the leaning it out. But still seems rather odd that one minute im overly rich and now it seems to draw air.

I've also removed the spring from the plate and the idle screw is out of the way.

Has anyone, any suggestions...as Im running out of ideas?

Cheers

Dan

[Engine Doctor]

Hi Daniel . Removing the spring was not a good idea. This allows the shaft to chatter and wear allowing air to be sucked past the butterfly. so get that replaced . It wont harm a servo pulling against it . The running rich suggest the diaphragm or needle vavle just below it letting by . Buy a complete carb overhaul kit this should sort problems . The air bubbles being drawn are bad for engines of any kind and need to be stopped Fitting a "T" piece in the fuel line is a bad idea also these can leak and allow air in as well as allow the engine to be flooded while filling the tank as suggested in your text . Fit a seperate fill and drain pipe to tank as well as a seperate breather pipe to the top of the tank . This should have a crimped end to stop fuel pouring out when tipped or being carried to the pits etc . The fuel line from the tank should be un broken apart from the pipe through the tank wall/bung to the clunk. Are you using a felt or sintered metal clunk ? these stop bubles from being drawn int the fuel pipe. these a re few bits to be trying

[Simon Chambers]

Are you using the stock spark plug or a NGK?

Si.

[Engine Doctor]

I forgot to mention the plug . As Simon says above scrap the stock plug and fit an NGK as a matter of course.

[Steve Dorling]

Petrol engine basics (two-strokes)

1 - New plug before anything else is moved, adjusted, fiddled with or altered..

2 - New plug cap

3 - Start the engine and look for leaks, air or fuel - bubbles or wetness etc - if all ok then FULL throttle and wait!

4 - Engine runs fine at full throttle, great - if not set the high end needle first and then LEAVE IT ALONE from that moment on - it only effects full throttle!

5 - Set idle needle - adjust 1/4 turn either side and WAIT - if the engine slows then you've gone the wrong way - the correct idle needle setting is when the engine is running fastest (i.e.optimum fuel-air - QED)!

Do any of this in a different order and you're chasing your tail

Hope that helps

[Browny]

Hi all, thanks for the suggestions.

Putting in a new NGK plug was the first thing I did im afraid.

The high end needle isn't the problem, its the bottom end, the only way I can get around this problem is to lean the mixture right out at idle. But then it hesitates and just about cuts out unless you pull the throttle back to idle. You can richen the mix up until its producing smoke at idle, the engine transitions rather well when you give it instant full throttle without any four stroking The odd thing i've found recently, is that if i leave the model sat for a day or two...then come back to it.

I can start it up and tune it fine, and runs as you'd expect it to. As soon as you stop the engine and restart it 20 seconds after it starts this hunting problem again. And then you cant rectify it at all after that.

As for the clunk, it's a plain metal clunk, which has never caused any trouble since the engine/tank was new, i've since isolated the tank from the fuselage, the bubbles have gone now. But the engine still has this persistant problem.

The engine has had about 1 1/2 gallons of fuel through it now, so its still relatively fresh. You can still see the honing in the bore.

I have had this problem for a while now, but not as severe as it is now. I even had it with the carb spring attached. I de activated it in the hope that it may have been the servo causing issues as i've got the TX set at full movement both ways at 125 i think it is. And believed it may have been hunting for this reason.

But the engine will still hunt if you bring the engine upto a fast idle.

Another thing to note, i tried misting brake cleaner around the carb gaskets. The engine didn't pick up in revs. It sort of just slowed and stopped instantly, im presuming the evapouration/cooling effect may have chilled the fuel?

As for a carb rebuild kit, does anyone know where i can obtain a kit in the UK?

The things for me to try at the moment is a new spark plug cap and a carb rebuild kit.

If someone could guide me where to get these from in the UK, it would be appreciated.

Cheers

Dan

[Browny]

Im suspecting fuel maybe a problem now. My last gallon of fuel was Shell Fuelsave Petrol. The old man was telling me they'd took both diesel and petrol fuel save off of there forecourts and replaced it with the old petrol forumla.

Read an article on a scooter forum earlier, which is the closest type of engine to a model engine. Stating that there having issues with fuel save fuel.

Although im not certain this is the cause of my erratic idle problems, i may have to dump the fuel and give it a go on fresh juice.

[Steve Hargreaves - Moderator]

Hi Daniel.....I can't help with the motor running problems I'm afraid but I AM interested to know how you find the Yak with a DLE 20 up front.....?

I quite fancy one myself & am musing over which engine to fit up front.....

[Browny]

Hi Steve, initially it felt quite good to fly although anything about half throttle doesnt seem to yeild any extra power and the throttle doesn't seem linear, In that it is very keen and aggressive at below half throttle. The exhaust system is purely cheap, the Zenoah ZG20 exhaust fits directly on and makes a considerable improvement to noise output.

It seamt to run quite well at first, as others have mentioned there a pain in the bum to prime by hand. But i usually just choke it and use the starter gun for ease.

Powerwise, its ideal for scale flying. It is capable of prop hangs and very steady pull outs.

Although I think if I could go back before i bought it, id have done more research and have chosen differently.

As its not that old and its been quite an adventure so far I have gotten away lightely with unexpected deadsticks recently on finals. I somewhat feel frustrated and somewhat a little let down, as the components could have been somewhat better. And i've had quite a collection of teething problems over the period ive been flying it.

Its been sat unflown for about a month now, which is a shame as when its running...its quite enjoyable and forgiving to fly.

[karl grey]

Hi Daniel, i'm the same as Steve as in not much help with the engine problems but i've not long had the seagull yak myself with a moki 135 fitted. Only had a hand full off flights with it but absolutely love it. Flew it saturday after crashing my sportster but wasn't daunted a bit while on the sticks.

Did have a few teething probs with the moki but replaced the bearings and it now runs like a dream with plenty of power on the vertical bits

[Steve Hargreaves - Moderator]

Thanks Daniel....interesting.....from what you say then the 20cc petrol pulls it along OK but doesn't set the world alight in the up, diddly, up, up bits......maybe a 26cc petrol is the way forward.

There seem to be so many engine choices for the Yak.....I've heard of ST23's DLE20's, 1.20 & 1.80 4 stroke glows........what to do, what to do...

[Mike Bell]

Dan, I have had experience of inconsistent low end running with a DA50 and it turned out to be fluff accumulation in the filter inside the carb. Worth taking the cover plate off the carb and having a look. There should be a domed wire mesh filter that you can take out and clean.

[Browny]

If you build momentum on the level then pull vertical, it will go with some pace. But pulling out of a prop hang its a little gutless. Maybe if i dropped to a 16 x 6 or 16 x 8 it may pull out better.

Hi mike, the carb is spotless...i've had it apart twice now and there was very little in there at first.

I've tried blasting all the ports through with brake cleaner, the only other thing i can do at the moment is try a different brand of fuel. Given that my last batch of nitro went off rather quickly and i suffered idling problems. Im starting to think it could be the extra ethanol that Shell claims is in there fuel, that may cause the problems? To me its as though the carb starts to boil the fuel after the first run.

It will run fine until you cut the engine. Restart it 10 seconds later and thats it...it gets the strop on.

Shifts have been slowing me down a little atm, that and i've been concentrating on building my fueling station for the turbine.

So the petrol has got put to one side until i find the enthusiams to try different fuel

[Rich too]

Hi Dan,

I have only just started using my first petrol, a Zenoah 23. Just a couple of thoughts.

1. Clunk - I went with a petrol filter clunk in the tank as some people had experienced problems not using one - better to be safe than sorry.

2. T piece - again, I researched this as I wanted a separate line for filling up. I read that some people had fuel problems using a T piece, so I decided not to use one.

3. Starting - my Zenoah did not want to know the first time I tried hand starting. Then I re-read the instructions (or at least somewhere!) and the recommended spot/position for the prop is pointing to about 10 o'clock at tdc (so well past the vertical) - what a difference that made, it now starts by hand easily.

It may be worth you going back to basics and at least eliminating these things. I have also just bought a DLE20 (based on lots of good reviews) so I hope it is as realiable as the Zenoah!! Good luck - Rich

Edited By Dickster on 16/06/2013 19:22:23

Edited By Dickster on 16/06/2013 19:25:12

Edited By Dickster on 16/06/2013 19:25:58

[Browny]

I'll bare these in mind Dickster, the engine used to run rather well from new, then started having these problems recently as the weather warmed up.

I've been and added 2 litres of Asda's fuel to the Shell Fuelsave id got left. I've not had chance to use it as of yet due to shift change and readying my turbine.

Many thanks for the input, i'll report back with my findings.

[Shaunie]

Have you tried fitting an air duct inside the cowling so that the carb gets fresh air rather than the secondhand stuff from the cooling fins?

Are you sure the exit ducts are large enough for the inlet area? I had cooling problems with my Edge 540 when I put an RCV91 in it. The remedy was to block off one of the air intakes so that all the cooling air went over the cylinder. Just sounds to me that, as you suspect, the carb is getting too warm.

Shaunie.

[Shaunie]

BTW I have to disagree with Steve D a bit on setting the idle mixture, most small petrol two-strokes need the mixture a little bit on the rich side, set them for max revs and they can run down and die at idle and have poor pick up.

My general rule from years of two-stroke motorcycles, hedge-trimmers, chainsaws etc. is listen to the behaviour when the throttle is closed sharply to idle. If it runs down to idle slowly and tends to die, it's too weak. If it drops a bit low and then picks up it's too rich. When it's right it will drop to idle and stay there.

Shaunie.

[Rich too]

Good point, try running it without the cowl for a while. I ran my Zenoah without the cowl to start with (mind you most of it hangs out anyway!) - Rich

[Paul Williams]

have you any means of testing the running temp? A cheap laser temp gauge is helpful. could be the fuel is evaporating in the manifold due to excess heat. This could be caused by a number of factors

I would try a new carb first. I disagree the top end screw should be left when set the setting up of these carbs is a balance between the two screws I have a data sheet from walbro with instructions how to set (PM me with your email address,) I would have to ask what has changed since it run ok, ambiant temp, cooling ducts have you removed any manifold gaskets.

[Rich too]

try it without the cowl before fitting a new carb! Rich ps there should be no bubbles in the fuel lines, get rid of the t piece!

[Browny]

I've ran it without a T piece, ive also ran it with the tank out of the fuz free of vibration.

I have had the cowl off with all of the recent problem solving. After all of my flights before the problems started you could hold the head without burning yourself, so i dont think its excessive heat.

A quick run down on the order of problems. It was fine for the first 10 flights, i then noticed that the engine was starting to rev up and down quite very quickly.

This never effected flight performance/reliabilty, i've ensured the engine was running slightly rich at all times as not to do damage. It wasn't causing any issues so i continued to fly it. It had a period where it settled down and ran normally. When i'd finished with the first 3-4 litres i opted to try some Shell Fuelsave (on the way to the field) Mixed up at 35:1

I probably had another good 8 flights after this, the next time i went to the field, i set up and started experiencing where the engine wouldn't start unless it was at full throttle. I tried a new NGK plug, starting at stock settings and trying to retune it again. No yield so it went back in the car.

Took it home did the carb lapping mods ensured all the filters were clean etc. Built it all up and fired it in the garden.

It sat there running rather well, no surging up and down on the revs. I thought brilliant, off to the field at the weekend. Started it up and it ran fine on the floor and for 15mins in the air, most of this was at half throttle and full throttle doing aerobatics.

I then made an approach for a landing, lowering the throttle to a fast idle whilst on the turn for finals. At which point the engine started bogging down, before id got to upping the throttle it deadsticked and turned into a really crappy glider forcing me to dump it in the rough.

I'm having a pretty bad run of luck with models at the moment, i've had a speedo's and servo's go pop in different airframes.

I've lost a 80" P51-D, The Yak is out of business because of this damn engine, That could be down to fuel, but i've not had chance to try the topped up fuel yet.

I hit a blender manouver pretty hard with my 3DHS Extra SHP. Ripping the battery out of its straps (yes more than one and a full bar of velcro holding it down the length of the lipo, launching it through the canopy and leaving the airframe in a very graceful inverted flatspin with no control

I've got a boomerang jet im having problems due to worn out locking mechanisms in the boom sections (luckily alshobbies have some intro parts on clearence at the moment)

I think im going to have to have a break for a few weeks and come back to it.

Cheers for the input guys, im definately going to hang around on this forum. Its been one of the most helpful ones yet.

[Mark a]

Your plan for having a break from it will do no harm. I did the same a while ago after in had destroyed my Wot 4 and Acro wot in the space of a fournight. Came back refreshed and ready to have another go and haven't looked back since and remember its only a hobbie so don't get stressed about it.

Edited By Mark a on 23/06/2013 09:33:44

[Browny]

Agree'd mark, although i dont think its purely just the hobby thats a problem. But collective stress isn't helping me at the moment. I've been having problems with Ghosted vision since last september, the work environment has been rather demanding. And ive been experiencing swollen lymph nodes in my honest opinion, and wisdom teeth. Which i think is the main cause.

This causes me severe pain behind the ears whilst wearing glasses. Which then gives me back and shoulder pains. The doctors havent been able to do much to aid me, physio has helped and the problem with my eyes aren't something that can be easily sorted. The past month i've felt the best health wise i have in a whilst. But in that time i've had a number of problems with models.

Wrecking my Miss America 80" knocked my confidence quite a bit, as it got a fair rock on trying to turn away from the trees (given its size i didnt realise how close i was) hitting it rather hard tearing the wing out of the fuzz and pretty much everything inside the fuzz with it.

I've just bought a Boomerang Intro 2nd hand, the engines sweet as a nut. Just the airframe seems to be showing signs of wear. Especially the clamping locking mech in the booms.

Im sure i'll get back ontop of things before long, but for the mean time. Im going back to fishing for a few weekends to "relax" lol

[Browny]

I'm still no closer to working this one out guys, its got to be either the ignition or carb now. I've tried filling my tank with fresh fuel to no yield. So I wouldn't say it was the fuel contributing.

Symptoms are still that the engine starts to bog down when you reduce the throttle, you can then lean the bottom end out and the engine starts to run at idle. But its hunting up and down the revs, you can lean it out a little more and it settles a bit more. But when opening the throttle, it gasps.

Richening the mix up until it transitions at its best, brings me back to the situation where at idle it will either stop rather quickly.

Or will start slowing down until it splutters to a stop.

Can anyone recommend a UK distributor for spark plug caps? And maybe any other parts im going to need (carb etc etc)

Cheers

Browny