sc 46 a

[Andrew Gardiner]

hi i need the help of your great minds.

i'm new to this game but i'm having trouble with my sc46 a engine it just cuts out for no reason plenty of fuel clunk is free and plug is fine i'm using model technics supaglow 10 fuel.
been told that it is the fuel as this is a running in fuel and the engine has now run in and wont run as well on it now.

any ideas as to weather this is right or any other possibilitys

thanks guys andy

[Phil Meredith]

hi andrew, fuel i fuel,
10 is just a higher nitro content that say sport 5, engines can cut any number of reasons, you say the plug is ok, have you tried a new plug, they behave differently out of the cylinder where there is zero pressure on them, do you check you needle setting with engine pointing up, hold the a/c verticle, (get help) hold it on full revs see if it falters, allow it to idle for 5 seconds and the open her up again if she messes about your mixture off, could be an air leak on one of the pipes, does it have a remote needle,
phil

[Andrew Gardiner]

hi phil

yeah i check needle setting b4 every flight and it is fine and all pipe work seems fine and no it does not have a remote needle have not tried new plug as the one in there is not that old as engine only just run in but i do have a spare so will try seems strange ran it on another guys fuel mostly syntetic oil and she ran sweet put her back on my fuel and she cut have heard that model technics fuel is crap anyway brought as shop only sells that fuel just seems strange she dont like to idle one time then then another time she'll cut mid flight

andy

[Phil Meredith]

had the same problem with an MDS 48,
i was the dead stick king at the flying club for quite some time, then i noticed fuel coming out of the cowel behind the spinner, turned out one of the carb O rings had split, replaced and no more probs,
most at my club use model technics, either sport 5 or contest 10, always thought it one of the best
phil

[Andrew Gardiner]

this supaglo is a high caster fuel and what i've been told is now the engine is run in it dont like the fuel now ran perfect on it at first now it hates it will try different fuel as need to get some more any way will get same fuel my club use and go from there but if you can think of anything it may be let me know.
there no fuel leaks at all on model just alot of caster down the side after each flight from silencer
andy

[Peter Miller]

If the engine cuts after some time check the clunk tube, it can get nicked when assembling the tank and then as the fuel in the tank goes down it exposes the tube close to the tank bung and allows air through.
I use Duraglow 10 on everything. I also use Taylor standard long reach plugs on everything and they work perfectly. Oh, I also use SC engines almost exclusively unless I can get a bargain on Ebay.

[winchweight]

As was said, if it once ran on it, it'll still run on it. I would start with the plug. Fit an OS No8 and try again. Although the plug isn't old, if you've used it during the run in, it could just be past it's best, what with alternating rich / lean running. Also check all the bolts, including the backplate fateners. The check that the carb retaining screws are tight, and the "O" ring is doing it's job.

[Peter Roberts]

I used to use Duraglo 10 all the time with good results but a bit messy.

I changed a couple of years ago to the ProSynth 2000 because I was impressed by the claims on reduced wear and corrosion and a conversation with them at a Sandown show.

I was astonished when I started using it that the mess was reduced significantly when compared with the Duraglo.

[Andrew Gardiner]

allready use os no8 plugs have changed plug and checked all tubes everything seems fine weather permitting i'll go up and give it ago today see what happens thanks guys i'll keep u posted

[Stovton51]

I had a problem very simmilar to this on my car so i took it to the garage the mechanic tinkered around with it for a while then he said crap in the carb I said "how often do I have to do that" he he

[Peter Miller]

Andrew, Did you check the tube INSIDE the tan for holes?

[Andrew Gardiner]

yes checked in the tank and all tubes fine do every thing i meant to use after run oil etc etc just cant understand why it cuts i'm sure it either fuel or idle setting but my instructor is addiment it's the fuel didnt get chance to fly today as weather is crap

[Roy SHAW]

Hi, Another reason for unexplainable cutting out could be that the copper tube from the exhaust pressurisation line has been nipped when shaping or fitting. This allows SOME air/exhaust pressure into the tank so that it starts and runs well on low throttle setting. Once you get going or have been flying for a little while not enough pressurising gas can get into the tank. A low pressure situation arises in tank, fuel won't go into the engine so it cuts out. It is surprising how small a nip in this line can cause the problem - it must be quite clear and free. Hope you solve the problem. Roy Shaw.

[Stovton51]

The recomended fuel is 5 to 10% nitro and the technics fuel you are using is at the top end of the spec the 10 only refers to the nitro content if any thing this fuel should make for easier starting and more power it may make it a little lumpy on tickover but thats all I personaly run the same engine on technics 5 for the run in and beyond,the engine is as sweet as a nut,what about tank position,try raising the tank to give a better head of fuel,try checking the exhaust nipple see if its clear,open or close low speed idle mixture to aid pick up,when does it cut out,if it's full throttle is the mixture to rich or lean,adjust to suit,if it's low throttle then the low speed mixture needs adjustment,glow plugs - are you using a plug with an idle bar if so change it,if not try one,its a bloomin minefield,good luck mate.

[Andrew Gardiner]

hi i have changed my fuel to prosynth 2000 5% and she has run fine never missing a beat for the last two days so it seems problem solved she just didnt like that fuel
thanks all for help
andy

[Tony Campbell]

Whoever told you that Duraglo 10 is just for running in, doesn't have a clue what they are talking about!! It never surprises me that there are people around, who, will make up utter rubbish to make themselves sound knowledgable.

For your information, Duraglo 10, is made up of:
Castor 6%, synthetic 9%

It is considered to be a modern 4 stroke fuel and recommended by Just Engines and RCV, to name just two.

Model Technics fuel is also one of the best fuel manufacturers on this planet.

I suspect that your Duraglo was contaminated in some way.

I would strongly recommend finding more informative club members to listen to, as it seems to me that you are at the learning stage and may end up being influenced by these idiotic story makers. Learning is always more fun when you are being taught by people who have real knowledge to pass on.

[Peter Miller]

Fuels can deteriorate. If left open they can absorb moisture and the Nitromethane and methanol can evaporate.
The worst example I saw was a model which refused to run on the field, it would start but was really sick, no power, rough and would stop after a few moments.
The owner checked everything then someone gave him af fresh tankful of fuel, problem solved.
I have only seen this once in many years though but diesle fuel could lose its ether very quickly.

[Phil Meredith]

i have been in the motor trade all my life, and have to say that geronimo and pete are giving realy sound advice, i always tell people, keep your engine runing on what it is used to, i know people that have chopped and changed there fuel like there socks, just because someone recomends something different, and have spent more time tuning and re-tuning there engines, i have used model technics contest 10 with all my engines from the word go, start with one fuel and stick with it,

[Andrew Gardiner]

hi all it was my local model shop that told me duraglo 10 was a running in fuel i just went in and asked for a running in fuel and thats what they gave me it was my club members who told me the fuel wasnt the best i could be using and i read that model technics wasnt that good and i will stick to prosynth now as it easier to get hold of round here

[Peter Miller]

Very few modern engines need much "running in" A tankful on a rich setting on the ground and then run it a bit rich in the air for a few flights. Flying figure eights which loads and unloads the engine are good.

ABC engines need to be run with short bursts at high speed. IF you run them slow and rich they don't expand as designed and so don't bed down properly.

Again this doesn't take long.

Basically, read the manufacturers instructions.

In the old days (Late 40s early 50s )some engines needed hours on the bench to free up, especially diesels.

Another thing which is important, never run an engine at the very peak speed, it is on the edge of running lean. Always bring it up to peak rpm and then back off the needle so you hear a slight rpm drop. The engine will still give plenty power but will last longer and if it does lean out it won't cook.

Finally, once it is set correctly DON'T twiddle with the needles. A properly set engine will run on the same setting for flying session after flying session. You might need a click on the main needle with major changes in weather.

[Tentpeg]

Couldn't agree more. We used to have a lot of needle twiddlers at our club, but they now refer to a reprint from a Steve Dorling article, pinned on the clubhouse wall. I reproduce here for your interest. Just follow this and you won't go far wrong...
ENGINE SET UP PROCEDURE by Steve Dorling.

1. Charge the tank to about one third full (only).
2. Open throttle wide and close the main needle completely.
3. Open main needle three full turns from closed.
4. Place finger over intake & rotate propeller 6 times.
5. Remove finger and close throttle to one third open.
6. Connect glow battery.
7. Start engine - either by hand or with a starter.
8. Gently (important) open throttle to flat out setting.
9. Remove glow clip (with extreme care).
10. Hold nose of model up at 60 degrees or so with propeller arc well clear.
11. Close main needle valve until engine rpm’s peak.
12. Open main needle one or two clicks from absolute peak rpm.
13. DO NOT TOUCH THE MAIN NEEDLE AFTER THIS POINT.


Part two: - IDLE NEEDLE ADJUSTMENT.

1. Close throttle to one quarter (i.e. fast idle)
2. Open secondary needle one quarter turn.
3. WAIT for 5 seconds and observe results.
4. If idle rpm SLOWS, close secondary needle back to where it was.
5. CLOSE secondary needle, wait five seconds and observe results.
6. If idle rpm speeds up then you are heading in the right direction – opening or closing the secondary needle slightly until the idle speed peaks is your goal.
7. Open throttle wide and check response.
8. If engine hesitates open secondary needle by just a click or two.
9. If engine splutters and throws fuel droplets from the intake, close the secondary needle by a click or two.
10. Open throttle wide and recheck the main needle setting with the nose of the model raised.



Steve Dorling adds, it is good advice from this point on to set the needles on your model and then reset them at the same time as you reset the needles on the vehicle that brought you to the flying field!
IN OTHER WORDS, LEAVE THEM ALONE & DON’T FIDDLE!