Jump to content

SC61A Carb Problem


Roger Dyke
 Share

Recommended Posts

40 minutes ago, Roger Dyke said:

The plug is an ENYA 3. About 2 years old (approx 10 flights) and looks fine to the eye. 

 

I will probably try a new one next time out with the plane.

What fuel do you fly, an old trick used mainly in the winter is around 5% petrol added to the fuel. 

  • Confused 1
Link to comment
Share on other sites

Advert


1 minute ago, John Wagg said:

I have an SC61 but not used for many years. I remember that also not having a good clean low speed idle. I wonder if a different temperature plug would help ? Possibly similar to an "idle bar" ?

 

Blimey Idle bars take me back. I've never needed one or used one. But I used to use Fireball Hot in most engines (NOT RACE) and they were fine. I used Taylor as well. I suspect that these aren't available these days. But yes sometimes playing with plug make can help.

Link to comment
Share on other sites

19 hours ago, Jim Hearnden 1 said:

Blimey Idle bars take me back. I've never needed one or used one. But I used to use Fireball Hot in most engines (NOT RACE) and they were fine. I used Taylor as well. I suspect that these aren't available these days. But yes sometimes playing with plug make can help.

Hi Roger. Jim has a point that might be worth checking ? I think that if plug is the cause (unlikely) it could be diagnosed by leaving power on it for bench  test or fitting a rc switchable power supply to plug in the model to see if any noticable difference to symptoms as fuel level changes. This will effectively advance the ignition timing .Those early Chinese engines did have very large choke bores that didnt help transition from low to WOT.

I would try the on-board glow and if unsuccesful look for a better carb from either a later SC/ASP or an OS .

Some plugs of yester year were ..... of dubious quality . I had a few that had such large bore for the element thst they effectively lowered compression enough to halve the engine power. 

I found this out on a new from box OS 20 FP. Started and ran very sweet with good idle but would only rev to about 4k. I changed fuel - no difference. Removed plug and then noticed this large bore, this was new plug I had fitted as OS came without one fitted. I cant remember the make but it had the large internal bore,possibly intended for use on engines that had to be shimmed for best performance. I dug out a used OS no 8 and viola it run very sweet with good pick up and nearly 10k

An Enya no 3 should be fine .... are they geniune Enya from a good source Roger as there are many fake plugs out there on the marke.

 

I think Jons hypothesis about tank hieght is possibly wrong . I can understand it if tank was completely above the carb center as if a Laser was fitted in that orientation but you say tank center line is inline with the carb center so should be fine as there is no apreciable head of fuel or ecessive lift needed when half full.

Similar set ups ie  head between 7 and 8 o/c was used extensively on many fun fly models like the Panic/ cougar etc etc with no throttling issues. 

I would be looking mainly at carb issues.... after all thats how ASP etc as they were back then earned their nick name as  All Spare Part and SC , Super C well you can work that one out as  t&c possibly wont allow me to write what I think ! But they changed, upped their products  into good engines. Do let us know what you find.

Edited by Engine Doctor
Link to comment
Share on other sites

Hi ED:

 

I don't think it would be possible to fly with an on-board glow battery permanently fitted as there is no extra room for anything.

 

I do have a brand new EYNA 3 purchased from a good source a short while ago which I am about to change. The fuel I have been using is Model Technics Laser 5 which is now running out and doesn't seem to be available for delivery from my usual supplier any more. Instead I am thinking of purchasing 5L of Optimix 5% to give that a try.

 

Tank dimension height is about 2" with the centreline about 1/4" below the carb needle. I have managed to secure a brand new carb (old stock) (not arraived yet), but am aware that it might be just as bad as the one I'm using, but probably worth a go.

 

I'm very happy with it's performance in the air. It's just the unpredictable throttle transition when the tank is starting to get low.

 

If I have to live with it I will, rather than hack the plane about for a "possible" improvement.

Link to comment
Share on other sites

On 13/06/2024 at 20:42, J D 8 said:

  Not done so myself but have known others to slim down the venturi with thin alloy tube, a couple of petals over top edge to keep in place.  This was with old MDS engines [ More Dead Sticks] to keep them going. Smaller venturi greater draw. Would it help here I don't know.

  Still recon the above would help a lot given the over size venturi that SC engines tended to have.

Link to comment
Share on other sites

If it is ok when the tank is mostly full, the simplest solution is to remove the anxiety by having shorter flights .... 🙂

 

You can get programmable on board glows that take current from your rx battery if space is very tight. I added one to my Valiant, which made flying it far more pleasant. The real answer would have been to lower the tank but I couldn't bear to hack about in a new airframe. My OBG is powered by a small 800mah LiFe which is about 2"x1"x0.5", the unit itself is about 1.5"x0.75"x0.5" (from memory). I've set mine up to be off if the throttle is above 30%.

Link to comment
Share on other sites

Model Technics Laser 5 fuel is now made by Optifuel (but still branded as Model Technics). It’s available from many model shops, their is a map showing stockists on the Optifuel website.

If delivery is required, Model Shop Leeds had it, either singles or in boxes of four.

Whoever can supply Optimix should be able to supply Laser 5 as well.

Be careful not to buy the low oil version by mistake.

The oil used is different now, and it’s red rather than purple, but if anything seems better than the old stuff.

Sadly the price has just increased, though it does come as 5 litres, so more than a gallon.

 

Brian.

Link to comment
Share on other sites

4 hours ago, RottenRow said:

Sadly the price has just increased

 

indeed. I plan to try the southern modelcraft equivalent as i suspect it will be a very cost effective substitute. 

Link to comment
Share on other sites

Have fuels moved on at all in recent times. What would be a good reliable glow fuel for general sport flying at the local club? I have been using MT Laser 5 until now but was thinking of trying Optimix 5%.

Link to comment
Share on other sites

On 14/06/2024 at 16:03, Jim Hearnden 1 said:

Blimey Idle bars take me back. I've never needed one or used one. But I used to use Fireball Hot in most engines (NOT RACE) and they were fine. I used Taylor as well. I suspect that these aren't available these days. But yes sometimes playing with plug make can help.

 

Ive got bout a dozen Taylor plugs in my flight box bought them on ebay recently unbused and still in original packets.. theres also one or two plus in my collection that also have idle bars,, I also use OS No.8 & OS F four stroke plugs

Edited by GaryW
Link to comment
Share on other sites

1 hour ago, Roger Dyke said:

Have fuels moved on at all in recent times. What would be a good reliable glow fuel for general sport flying at the local club? I have been using MT Laser 5 until now but was thinking of trying Optimix 5%.

That's a can if worms... people seem to have strong opinions on glow fuel.... you're going tk be told "brand A is rubbish, only use brand B", and "brand B is rubbish, only use brand A".  I presume enough people are happy with brand A AND brand B to keep them in business..

 

  • Like 1
Link to comment
Share on other sites

7 minutes ago, GrumpyGnome said:

That's a can if worms... people seem to have strong opinions on glow fuel.... you're going tk be told "brand A is rubbish, only use brand B", and "brand B is rubbish, only use brand A".  I presume enough people are happy with brand A AND brand B to keep them in business..

 

 

My go to fuels are Model Technics Contest 10 more so as I normally run it in my helis or Southern Model Craft 10% Synthetic for all my engines 2 stroke & 4 Stroke,,, & SMF Sport Mix Diesel for my glider.... I did try Rapicon in a heli once...... Hell it turned my heli into a flying smoke machine the fuel was so smokey and nearly choked the whole flightline.... lol

Edited by GaryW
Link to comment
Share on other sites

2 hours ago, Roger Dyke said:

Have fuels moved on at all in recent times. What would be a good reliable glow fuel for general sport flying at the local club? I have been using MT Laser 5 until now but was thinking of trying Optimix 5%.

 

They have moved on but not from the laser 5 fuel you have. 5% nitro with 15% synthetic oil is all you need for any 2 or 4 stroke fixed wing engine. Cars, boats, helicopters, there are different requirements so slight changes are needed to the fuel. 

 

The optimix 5 uses more oil than the laser 5 and would be a backwards step. 

Link to comment
Share on other sites

34 minutes ago, Roger Dyke said:

Oops... Forget the above question. It is obvious it was the 15% oil. sorry about that.

Definitely dont use the low oil version of Laser mix . It was intended only for the latest Laser engines  . The 15% oil is good for most if not all our engines 

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...