Go Back  RCU Forums > RC Airplanes > "1/2 A" & "1/8 A" airplanes
Reload this Page >

SC 12 Engine problems

Notices
"1/2 A" & "1/8 A" airplanes These are the small ones...more popular now than ever.

SC 12 Engine problems

Old 02-25-2011, 02:38 AM
  #1  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default SC 12 Engine problems

Not sure if this is the right forum for this post, but I guess a .12 size engine falls in the 1/2 A category...

I have a pair of SC 12's that I bought about ten years ago, and have barely used. I got these out recently to use on an All Star bipe, and I've had all sorts of problems.

One of the engines starts fairly easily but runs unreliably and doesn't generate much power. The other one won't start at all.

I had the prop fly off the one that runs (loose prop nut) and of course the revs went very high, and I think that might have damaged it. I can't be sure, but it seems that since then it is decidedly less powerful now than it was before the incident.

Does anyone have experience of this? Could the over-revving have damaged the engine?

And if anone has any tips starting the second engine I'd like to hear them.


Old 02-25-2011, 06:26 AM
  #2  
alcarafa
 
alcarafa's Avatar
 
Join Date: Dec 2006
Location: MEXICO, MEXICO
Posts: 786
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

You can get some help in the glow engines forum also:
http://www.rcuniverse.com/forum/forumid_114/tt.htm

Hope it helps you.
Old 02-25-2011, 07:05 AM
  #3  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: SC 12 Engine problems

These are very good engines for the price. Max prop is an apc 7x4 (the 6.3x4 and 6.5x5 are better ones) and don't use too much nitro, <10% is enough. On hot summer days I have also added a washer to be able to run 10% without over heating.

For any glow engine to fire you need the following:
- fuel
- working glow plug
- compression

If it doesn't even fire you are missing one or more of the above...
Old 02-25-2011, 08:08 AM
  #4  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

Thanks everyone. Both engines fire. One runs but not particularly well, the other one won't start at all, so I'll concengrate on the one that runs...

I am using 16% nitro and an 8 X 7 prop. If 7 X 4 is the max then presumably the wrong prop could account for the lack of power and reluctance to idle.

Will 16% nitro cause problems? Will it make the engine run too hot?

Mr Cox do you mean you add a second washer under the plug? Is there a plug that works well with these engines?

Thanks again.
Old 02-25-2011, 10:15 AM
  #5  
DeviousDave
Senior Member
 
Join Date: Feb 2007
Location: , MI
Posts: 1,781
Likes: 0
Received 1 Like on 1 Post
Default RE: SC 12 Engine problems

You say both engines fire, but only one will stay running. The one that won't stay running has one of two problems: Fuel delivery or an air leak related to temperature expansion.

Take the carb of the better motor and put it on the one that won't run and come back to us with the results.
Old 02-25-2011, 11:30 AM
  #6  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: SC 12 Engine problems

an 8x7 prop is for engines twice the size or larger, you really should use a smaller prop. To me there is no point in propping it for anything below 15 krpm. On 10% nitro one of my engines was not running well on hot summer days, so I then added an extra gasket (about 0.10mm) under the head and that fixed it. It now does about 15500 rpm on an APC 7x4 (and idles down to 2500rpm). With the apc 6.5x5 it really comes to life and spins that at 17500rpm (18200rpm without the muffler).

You can run it on 16% nitro but you should then shim the head for a lower compression. It is not very picky with the glow plug, any long or medium plug will do. I have run OS#8 in the summer and A3 in the winter. Enya 3 and 4 works too. As the these are dubbel ballbearing and true ABC you can run them on synthetic oils if you want to. I have one engine that has now done two seasons now on purely synthetic oil (as a test) no problems at all and the inside is ridiculously clean, looks unrun.

If the engine fires but does not keep running I would clean the carb and check the low speed needle. These are operational all the way almost up to full throttle. If it is set too lean it can actually even screw up the full throttle setting too, you'll know that when there is no response to the main needle setting.

If you have lost the prop and the engine reved up, you might want to check the conrod to make sure that it is not bent.
Old 02-25-2011, 12:07 PM
  #7  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

Thanks for this Mr Cox! I'll see if I can get hold of a 6.5 x 5 next week and try it with that.

I'm pretty sure the low speed needle is not set right too, so I'll read up on how to set that. If as you say it can affect the performance even at full throttle then that could be the source of the problem.

Coupled with the enormous prop it sounds guaranteed to give me marginal power...

Devious Dave - the second engine doesn''t even run for a short burst, so I don't think the carb is the problem, but i'll swap them over and see what happens. The second engine will fire once or twice when i spin the prop. Can't get any more life out of it than that. I've swapped plugs and I'm using the one that works in the 'good' engine, but still no life...



Old 02-25-2011, 12:29 PM
  #8  
ffkiwi
 
Join Date: Jul 2005
Location: Upper HuttWellington, NEW ZEALAND
Posts: 1,601
Likes: 0
Received 1 Like on 1 Post
Default RE: SC 12 Engine problems

cuica-you state your fuel is 16% nitro-this is a % that I associate with R/C car fuel blends-and most RC car fuels have a low oil %-what oil % is your fuel? Some RC car fuels are as low as 12% oil. If you are using RC car fuel in your SC-the low oil content might well be contributing to your problems! You've already put the engine under some stress by overloading it with too big a prop-which on a glow will result on overheating-if at the same time your fuel is low in oil-the overheating will be worse-so its no wonder you're lacking in power. As for the other one-all I can suggest is following the other suggestions you've already been given. And check what the oil content is by %-some of the cunning manufacturers express it as w/v 'weight per volume' rather than than v/v-the true % value.
One point that may or may not be relevant (it will depend on how old your engine is)-SC's come from the same factory as the ASP engines-in fact they ARE the same engine with a different badge. The earlier produced ASPs had a problem in that, for production economics, the factory tried to use the same size carb on a range of different displacements-the result of this was the smaller engines-12, 15, 21 25 had carbs that were too big, and had running, fuel draw and idling problems, while the bigger ones had carbs that were too small and limited the power output. The later ASP series 3 range don't have this problem.
If your SC engines are of the earlier production variety-then this could also be a problem with your engines.

FWIW-an 8x7 is a size I would use on a 21 or 25 engine-and on a fast model at that. Much much too much load for a 12 engine

ChrisM
'ffkiwi'
Old 02-25-2011, 12:52 PM
  #9  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

Hi ffkiwi - Note taken of the too large prop. Will get a better suited one asap!

Yes the fuel I am using is from a car shop. I am in Greece where the model shops are very poor and it is hard to get supplies, much less a knowledgeable opinion. Most places sell a few ARF models and not much else.

I'll see if I can find some better suited fuel too...

My engines are about 10 or 12 years old, so not sure where that would put them with regard the size of the carbs.

What a great forum this is, and how nice to have so many useful suggestions. Thanks all!

Old 02-25-2011, 02:37 PM
  #10  
ffkiwi
 
Join Date: Jul 2005
Location: Upper HuttWellington, NEW ZEALAND
Posts: 1,601
Likes: 0
Received 1 Like on 1 Post
Default RE: SC 12 Engine problems

cuica-look very hard at your fuel bottle-and try and determine what the oil content is-perhaps go back to the shop and see if they can tell you if it isn't clear on your container. If it turns out to be low at 10-16% oil as I suspect it might be, you can add more oil to bring it up to a safe level of 20%-obviously this will lower the nitro % proportionately, because you're increasing the volume, but that won't have a huge impact on the way the engine runs. You'll be far better off with 20% oil and 10 or 12% nitro than with 10 or 12% oil and 16% nitro! The simplest method would simply be to buy a 100ml bottle of medicinal castor oil-which you should normally be able to get at a supermarket or at worst, a pharmacy, reasonably cheaply -and add this to a litre of fuel-that would virtually double your oil content, if the fuel was only around 10% originally (and this is the figure we don't know in this case-what the original oil content was) and your nitro only drops to 14.5% -which you wouldn't even notice the difference.
Bear in mind that if my suspicions are correct about the oil, you may already have caused some engine damage or excess wear through low lubrication AND an oversize prop-you won't be able to recover this, but increasing the oil content should prevent any further disasters.

I can't comment much further on your engine age with respect to the carb sizes-at the age you've given-they could fall into either the early production or the later improved models. Certainly around 2002 I was buying the later series 3 ASPs from Just Engines in the UK, and the carb problems had been well and truly sorted out by then! One indication might be to check the spigot diameter-that is the outside diameter of the carb neck that plugs into the crankcase-measuring off a relatively recent ASP 15 (which shares the same crankcase as the 12)I have here- this is one of the 'series3' range models-not the very latest ASP 15, I measure 9mm OD. If yours measures more than this diameter, it would indicate that you have one of the early ones-and potentially the additional issues I referred to in my first response to this thread. The carb bore is a snid over 5.5mm on my carb (measured by stuffing the nearest size of drill that fits-a recheck with vernier calipers gives it at 5.6mm. Again- if your carb ID measures much bigger than this you might experience fuel draw and poor throttling problems.

ffkiwi
Old 02-25-2011, 11:18 PM
  #11  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

Thanks again ffkiwi. The bottle says nothing about the oil content, but to be on the safe side I'll add castor oil. At worst I'll have wasted a bottle of fuel, but since I bought it at an RC car shop it sounds pretty likely it is 10% oil as you and others have suggested.

The carb seems to have a bore of 5.5mm by the drill bit test, so that's something!
Old 02-26-2011, 04:41 PM
  #12  
fit90
 
Join Date: Jan 2010
Location: naples, FL
Posts: 141
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

ffkiwi,

It is good to see you posting.  I have seen some terrible images on the news in the U.S. from the earthquake.  I hope that you and all your friends and family are safe.

Bob
Old 02-26-2011, 05:46 PM
  #13  
DeviousDave
Senior Member
 
Join Date: Feb 2007
Location: , MI
Posts: 1,781
Likes: 0
Received 1 Like on 1 Post
Default RE: SC 12 Engine problems


ORIGINAL: cuica

Thanks for this Mr Cox! I'll see if I can get hold of a 6.5 x 5 next week and try it with that.

I'm pretty sure the low speed needle is not set right too, so I'll read up on how to set that. If as you say it can affect the performance even at full throttle then that could be the source of the problem.

Coupled with the enormous prop it sounds guaranteed to give me marginal power...

Devious Dave - the second engine doesn''t even run for a short burst, so I don't think the carb is the problem, but i'll swap them over and see what happens. The second engine will fire once or twice when i spin the prop. Can't get any more life out of it than that. I've swapped plugs and I'm using the one that works in the 'good' engine, but still no life...




If you have a good glowplug and it won't even fire on the prime, then it is a compression problem. Does the motor feel like it has any 'pop' when you flip it over? How are you priming it? Does the plug glow bright orange?
Old 02-27-2011, 12:47 AM
  #14  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

Both motors feel like they have about the same compression. The non starter feels fine from this point of view, but perhaps a little tighter inside the liner than the runner, which turns over quite freely.

I've tried priming it various ways, holding a finger over the air intake and flipping the prop a couple of times, to pouring raw fuel straight into the carb.

The one that runs seems very sensitive to flooding, and generally wants very little priming.

I'll get hold of a correct sized prop and have another go!
Old 02-27-2011, 03:19 AM
  #15  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: SC 12 Engine problems

Yes, they are easily flooded when priming though the carb, for the first runs you can instead prime the side of the piston the classic way (without a muffler mounted). If it does get flooded then hold the engine rotated at 90° with the exhaust pointing down to get the fuel out.

It may also want to run backwards when primed too much, you can then start it by bouncing backwards on the compression. It is important to have enough power to the glowplug, dark red is not enough if you overprime the the engine, it should be bright yellow.
Old 02-27-2011, 04:58 AM
  #16  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

So should I use a hot plug? The one I am using is medium, can't remember the brand...
Old 02-27-2011, 06:02 AM
  #17  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: SC 12 Engine problems

Medium or hot plug doesn't really matter that much, that is for final fine tuning of idle and throttle response.
Oil content in the fuel is far more important. I have used 17% fully synthetic in one as a test and it works fine, I'm more used to 20% all castor.
Old 02-27-2011, 10:49 PM
  #18  
DeviousDave
Senior Member
 
Join Date: Feb 2007
Location: , MI
Posts: 1,781
Likes: 0
Received 1 Like on 1 Post
Default RE: SC 12 Engine problems


ORIGINAL: cuica

Both motors feel like they have about the same compression. The non starter feels fine from this point of view, but perhaps a little tighter inside the liner than the runner, which turns over quite freely.

I've tried priming it various ways, holding a finger over the air intake and flipping the prop a couple of times, to pouring raw fuel straight into the carb.

The one that runs seems very sensitive to flooding, and generally wants very little priming.

I'll get hold of a correct sized prop and have another go!

Hmm.. One engine is more sensitive to overprime than the other.... I'd still give swapping the carbs a shot after trying the following:

Start it with the needle fully closed. Just do short runs on the prime by giving it fuel thru the exhaust port. When you get the amount of fuel in the exhaust port figured out for a good running burst (do this with the muffler off) continue to do runs on the prime but open the carb needle 1/4 turn each attempt until it runs.

Old 02-28-2011, 01:12 AM
  #19  
ffkiwi
 
Join Date: Jul 2005
Location: Upper HuttWellington, NEW ZEALAND
Posts: 1,601
Likes: 0
Received 1 Like on 1 Post
Default RE: SC 12 Engine problems

Bob-I'm actually in Wellington (the capital) these days-I moved up here from Christchurch Jan last year-just haven't got around to editing my profile to update the location yet. Most of my friends and family have come through alive and uninjured-but not necessarily undamaged. The assessment is that things are about 5 times worse than Sept 4 last year.Things are really bad down there-the current 'official' death toll is around 150 (148 last time I checked) but unofficial (thru the mil net) says somewhere between 180 and 190-with 200+ listed as missing. Many of the missing are already in the morgue, but not officially ID'd yet-so its hard to say what the final total will be-not necessarily the sum of the two figures-but the death toll overall will probably go over 300. It is real 9/11 stuff-just fragments of bodies in many cases-there are Israeli and Thai forensic teams (both countries with extensive experience in forensic identification in recent times) working hard to assist our police and emergency authorities in casualty identification.
Our former Prime minister, Helen Clark-now with the UNHCR, visited over the weekend and said the damage was as bad as anything she'd seen last year in Haiti. Current estimates for damage are 16 billion and rising, and between 25% and 1/3 of the buildings in the CBD are so badly damaged they will have to be demolished. 52,000 people work there-and the majority of their jobs are currently under threat-most of the small shops, cafes, boutiques, books stores and other small businesses will likely go under as a result of the quake flow on effects on business.

I personally think it will take the best part of a decade for Christchurch to recover from this one-doubly hard to accept when the city was still struggling with the aftermath of the Sept 4 quake last year, and the Boxing Day aftershock as well-but those whilst causing extensive damage, did not result in the catastrophic damage and death that last Tuesday's quake has inflicted.

ChrisM
'ffkiwi'
Old 02-28-2011, 01:53 AM
  #20  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

ffkiwi this sounds awful and my thoughts are with those affected.
Old 02-28-2011, 10:39 PM
  #21  
ffkiwi
 
Join Date: Jul 2005
Location: Upper HuttWellington, NEW ZEALAND
Posts: 1,601
Likes: 0
Received 1 Like on 1 Post
Default RE: SC 12 Engine problems

ORIGINAL: fit90

ffkiwi,

It is good to see you posting. I have seen some terrible images on the news in the U.S. from the earthquake. I hope that you and all your friends and family are safe.

Bob
I hope you will excuse the off topic picture-but here is an amazing picture I was sent today of the exact instant the quake struck Christchurch-12.51pm local time (NZDT), Tues 22nd Feb. The picture was taken from one of the SE hill suburbs-probably Cashmere, looking N over the city centre, by an unknown tourist. I think it will become one of the classic images of the Christchurch quake. You can just see the CBD high rise buildings through the dust cloud triggered by the shockwave. Interesting to see that it appears to have a largely vertical rather than sideways component to it.

'ffkiwi'
Attached Thumbnails Click image for larger version

Name:	Vt58787.jpg
Views:	58
Size:	56.1 KB
ID:	1571649  
Old 03-01-2011, 08:41 AM
  #22  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

Amazing!
Old 03-12-2011, 10:42 AM
  #23  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

I've finally managed to try the engine out with a smaller prop, and the difference is incredible!!! The revs are very high - I don't have a meter but at full throttle I would describe the pitch as 'screaming'.

The engine is on an Ace all star bipe and the power is enough to *almost* make the plane hover vertically, so must be more than enough to get it flying.

Idling is great - really slow, just a tickover. Opening the throttle fully from idle causes no problems provided the mixture is set just slightly rich.

The only problem I have is that sometimes the engine can be very hard to start when it is hot. I have a feeling that this is to do with it being flooded but I'm not really sure. I'll start it, have it running fine, then shut it off. Try to start it again and sometimes it wil burst into life, other times it just won't respond, and the only cure seems to be to leave it to sit for a while and them try it again.

I'm using a 7x3 prop and the 16% nitro fuel with 10% castor oil added.
Old 03-12-2011, 12:56 PM
  #24  
Mr Cox
 
Mr Cox's Avatar
 
Join Date: Jul 2007
Location: Karlstad, SWEDEN
Posts: 3,791
Likes: 0
Received 2 Likes on 2 Posts
Default RE: SC 12 Engine problems

Regarding the restart, it is very common that restarts are a little harder then cold starts. It might be set a little lean on the low end so that it relies on a proper prime to start, nothing to worry about if it runs fine otherwise. Once cooled down you'll also have a better seal between the piston and cylinder which helps the restart. Compared to some old school engines (e.g. Enya 09) my ASP is very easy to start when hot.

As you use it more you will also learn just the right amount of prime. It should feel a little sloppy when turned over (without power to the glow plug) and then it will fire right up when the glow-power is attached.
Old 03-13-2011, 01:54 AM
  #25  
cuica
Junior Member
Thread Starter
 
Join Date: Feb 2011
Location: Nafplio, GREECE
Posts: 19
Likes: 0
Received 0 Likes on 0 Posts
Default RE: SC 12 Engine problems

I flew the biplane with the SC12 for the first time today. The engine was reluctant at first but when I got it going had bags of power and idled fine as before.

The flight was nerve-wracking (haven't flown any models for quite a few years) but I managed to keep it in the air for a brief flight.

Power was more than adequate, and it would maintain altitude at about 1/2 throttle. It's a fast and twitchy model (coupled ailerons on upper and lower wings...), also a little overweight which doesn't help, and I need something slower to get used to flying RC again.

But it flew, and suffered only very minor damage to one aileron on landing, so I'm happy.

I have a .25 sized high wing cabin model on the go - will relearn on that before flying the all star again I think!

Thanks for everyone's help and advice with this one!!

Thread Tools
Search this Thread

Contact Us - Archive - Advertising - Cookie Policy - Privacy Statement - Terms of Service -

Copyright © 2024 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.