OS 52\sc 2 stroke low RPM settings & high RPM settings how many turns ? for both ..cuts out going to full throttle ...

[RAF]

Hi All , Tuff one this ... before we start a little history ,,second hand engine seen it flying, about 3 years old , Currently set up in a Cessna, Tank and fuel lines new, Tank correct level ..Engine is on its side ,I  do believe this makes no difference to running conditions ...Currently low RPM is set to 3 turns out anti clock wise from its stop point ...& High RPM is set to 2 & half turns out from its stop point . i don't have manual ,and  I have moved low RPM settings by half a turn either way , The problem is it wont go to full throttle and dies ,if i open low rpm screw to much it runs but dies when you take glow plug off , and still no full throttle in that setting ...are the settings correct??... I'm using a 1.2v rechargeable batt @ 2.2mah which glows the plug nicely ...I have 6 of them which gives me 6 hours could anyone help with the above issue please as i am struggling ....using 10% nitro ,,,I wanted the old school castor oil but no stock for now ,  so using red synesthetic stuff not fond .. This is not a 4 stroke ...This model is the 2-stroke type with curb at the back of engine ...From what i have read about these engine is that they are problematic but reliable  ......thanks ....

 

 

Kind Regards,

Raffaele ..

Edited November 6, 2022 by RAF

[RAF]

i can break this down in segments if required thank you 

 

 

Kind Regards, 

 

Raffaele

[Denis Watkins]

A glow plug which has lost its catalytic properties will produce a run like this.

1st change the glow plug, then try again.

if the tuning is out

try this

In a quiet place, you can set the low needle with a piece of fuel tube on the carb, long enough to blow down.

Set the barrel on low idle, by hand, about 20-25% open.

Blow down the tube and you may or may not hear the air hissing.

Open the slow jet, turning counter clockwise, to hear a hiss

While blowing, turn the low needle clockwise slowly, - slowly -

Until the hissing just stops

Then open very slowly until the hiss just starts again

 

You are now very close to the correct low end tune

Edited November 6, 2022 by Denis Watkins

[RAF]

thanks Denis ,,, can i do this with curb in situ ?? or pull curb off ??

[RAF]

i have several types of plugs tried them all ,,number 8 seems to work best for now ,,

[Denis Watkins]

Yes RAF, Carb on and motor intact

[Don Fry]

RAF, straight advice, you need hand on help from someone who runs motors. This can be remote advised, but a caution.

The questions asked suggest these things are not familiar to you.

Its going to require you to adjust it when it’s running.

Get that wrong, if you are on your own, it can render you unable to drive to the hospital. Not a toy, a finger remover.

Do you want to proceed on that basis.

[BackinBlack]

You mention having 6 batteries that will give an hour each. Are you disconnecting the glow plug once the engine is started?

[RAF]

51 minutes ago, Don Fry said:

RAF, straight advice, you need hand on help from someone who runs motors. This can be remote advised, but a caution.

The questions asked suggest these things are not familiar to you.

Its going to require you to adjust it when it’s running.

Get that wrong, if you are on your own, it can render you unable to drive to the hospital. Not a toy, a finger remover.

Do you want to proceed on that basis.

thank you for your advice ..have help on hand if it go's south , will try blowing down inlet port of curb and set it by listening for small hiss sound ,,bit tricky as motor is on its side and screw is difficult to reach ,unless bench test again .....ill keep you posted ..still not sure what factory settings are yet .. on low rpm mixture and high rpm mixture..Have had motors in the past etc ...going back to it, had enough of battery flight times ..

 

 

Raff

[RAF]

33 minutes ago, BackinBlack said:

You mention having 6 batteries that will give an hour each. Are you disconnecting the glow plug once the engine is started?

yes indeed ...they are all back ups for when out on the field ...i find they dont last long 20 starts from one fully charged ...how long do yours last ?

[Jon H]

2.5 turns on the main should be more than enough fuel. 

 

My gut feeling is fuel starvation due to a blockage/bubbles but to be sure we need to break down the issue a little more. 

 

You say it wont go to full throttle. ok but how? Will it make it to full power if you coax it open slowly but dies if you slam the throttle open? or will it not open up at all?

 

Next, how does it die? Coughing and spluttering or power fade/instant death. This is important as coughing and spluttering suggests a rich cut, power fade a lean cut. This helps figure out where you are with your tuning and where to go next

 

Everything the other guys have said is fair enough as well and worth following through on. 

 

With slow run tuning make life easy and phone a friend. Stand the model on its wing tip and get them to hang on to it. You can then adjust away with relative ease. you still need to be careful but its much safer and quicker than any other method. 

 

It might also be handy up upload a video of the problem. The sound and behaviour of the engine is very informative when it comes to diagnosis. Just keep the camera out of the prop wash to prevent excess wind noise. 

[RAF]

Hi Jon,

 

 

ok your first point : yes if you coax it up slowly it just makes it then dies  no spluttering ,just fades out .

 

point 2: fades out , no spluttering . 

 

Today i have seemed to have got a better low rpm setting using three and a quarter turns ,  high rpm setting is now at 3 and a half turns,seemed alot ,but now theres better run times and responce ,, ..Still not happy to fly with this yet ....

I found theres not much technical data out there regards to OS 52SC Two Stroke...Plenty of fours ...lol

 

 

King Regards,

Raff.

[Frank Skilbeck]

Do you mean SC52, I can't find an OS52 two stroke anywhere, SC were designed and made by completely separate company to OS, SC and ASP are identical apart from the name so you can search for information for both an ASP or SC52.

 

I have run several of these, but not the 52, they all ran well, the symptoms you describe could indicate

 

1) partial blockage in the carb, can you check that there is no debris in the carb jet. It only needs to be very small and it will partially block the needle.

2) front bearing passing air, this allows air to be pulled in through the front bearing, effectively leaning the mixture.

 

BTW the ones I have run have always been on synthetic oil and had no running problems.

[Jon H]

Yep i agree with frank. 

 

It sounds like you are suffering from a lean mixture at full power and you need to work out why this is before getting to excited about the slow run needle as you cannot set the slow run without the main needle already being right. 

 

ASP/SC engines also suffer from air leaks round their main needles and this could potentially be an issue. Again for clarity it would be best to post a video of the engine running as is much easier to identify the problem

 

I had a pair of ASP 52 2 strokes in a twin and they ran very well. I was using straight fuel with synth/castor mix at the time...cant remember why. Anyway they flew my ripmax harmony very well indeed.  

[Engine Doctor]

If you are still experiencing difficulties with running check the plumbing agian especially any brass tubes in the tank . Nitro in the fuel dissolves the copper content in the brass over time leaving perforated zinc behind. If you model has stood around for a while then the rotten pipe problem is very likely.

Then check the carb for debris  . One part often forgotten is the chamber that the fuel nipple screws into . I've found debris there  in a few carbs over the years when the owners have almost given up on the engine.

While your stripping the tank to check the pipes take the oppertunity to replace the clunk with a sintered metal clunk.  These only cost £2 or £3 and will tottaly stop any debris getting into the carb/ engine. It's also worth fitting one in the fuel bottle in your flight box then fuel is double filtered by the time it gets to the engine. Let us know how you get on.