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Is it possible to rotate the throttle arm on the SC52 four stroke?

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JohnnyB10/08/2020 20:03:44
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262 forum posts
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Hi everyone,

Recently I’ve been doing quite a lot of head scratching trying to figure out if it’s possible to rotate the throttle control arm of my SC52FS motor through 180* so that I can connect the control to the servo from the bottom position instead of the present top position.

I’ve removed the screw in the hub of the barrel which attaches the arm, and also the screw behind the throttle arm, but to no avail regarding being able to rotate the position of the control arm!

Hoping someone can help.

With Kindest Regards,

John.

Martin Harris10/08/2020 20:29:21
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9501 forum posts
256 photos

There should be a grub screw on the outside of the arm's boss. Release it a half turn or so and you can reposition the arm.  It might have seized - push the arm round to break the corrosion...

Edited By Martin Harris on 10/08/2020 20:31:02

Peter Christy10/08/2020 22:28:22
1873 forum posts

I've done it on an ASP30FS, and I would imagine the SC is similar. Forget what I had to do now, but I know it wasn't difficult.

--

Pete

Jon - Laser Engines11/08/2020 08:54:45
5621 forum posts
271 photos

you just need to undo the black nut (see photo) that holds the arm. Be careful when you tighten it though as you might crack the barrel if you go mad.

When you say 'screw in the hub of the barrel' what exactly do you mean? if its in the end (red arrow in photo) that is the slow running needle and you will need to retune it when you get it all back together

asp-airplane-fs52ar-engine-carburetor-assembly-four-stroke-accessories.jpg

Engine Doctor11/08/2020 11:26:50
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2588 forum posts
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If you carb is the same as John shows above then do as he says.

If your carb is like this ;SC ,ASP etc changed their stuff occasionally

capture sc 52 carb.jpg

Then there will be a small grub screw in the alloy ring behind the arm (1.5 mm allen key I believe) . Loosen this and rotate the arm to desired position and re tighten. Warning : Use a good quality allen key/driver or you risk the possibility of rounding the corners as these arenot the best quality grub screws .

Its possible that the arm has been assembled with thread lock or similar to loosen it just remove the barrell and heat the whole item and any adhesive will loosen .

Edited By Engine Doctor on 11/08/2020 11:28:26

Martin Harris11/08/2020 12:14:20
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9501 forum posts
256 photos

For the avoidance of any doubt:

img_0390.jpg

...the black grub screw is visible in the middle of this photo.

Edited By Martin Harris on 11/08/2020 12:15:09

Jon - Laser Engines12/08/2020 08:27:14
5621 forum posts
271 photos

i think the 30-65 had the carb i listed and the 70 onwards had the type with the grub screw. The grub screw type is a better design as its so easy to break the other one and you loose the slow run setting when you adjust the throttle arm. I think i broke 2 on an ASP61 as they clearly went a bit mad when they hardened it and they broke like a carrot.

Martin Harris12/08/2020 11:05:14
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Maybe the OP will update us with his progress but the ASP version certainly uses the arrangement I pictured in addition to your version as an alternative fitting which I suspect was fitted to earlier versions.

Whatever, I suspect he'll be needing some advice on setting the slow running screw when he sorts the throttle arm:

"I’ve removed the screw in the hub of the barrel which attaches the arm"

 

Edited By Martin Harris on 12/08/2020 11:08:17

Jon - Laser Engines12/08/2020 14:03:46
5621 forum posts
271 photos
Posted by Martin Harris on 12/08/2020 11:05:14:

Whatever, I suspect he'll be needing some advice on setting the slow running screw when he sorts the throttle arm:

Edited By Martin Harris on 12/08/2020 11:08:17

That's easy, start engine and twiddle it until it runs good

If it wont start, twiddle it until it does!

Martin Harris12/08/2020 16:15:45
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...and if he's anything like a lot too many model flyers, once it's been set up right, twiddle it until it doesn't run properly any more!

Petrol Pete12/08/2020 16:27:47
16 forum posts

hi, I have swopped the carbs round on os's before by just taking the two screws that attach carb body to backplate, turn it 180 degrees and refit screws job done

Jon - Laser Engines12/08/2020 16:42:28
5621 forum posts
271 photos
Posted by Martin Harris on 12/08/2020 16:15:45:

...and if he's anything like a lot too many model flyers, once it's been set up right, twiddle it until it doesn't run properly any more!

Ha! too true

PP, he wants to move the throttle arm not rotate the carb to the other side.

JohnnyB17/08/2020 09:54:06
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262 forum posts
38 photos

Hi everyone,

Thank you everyone for all of your comments regarding my query. I really appreciate you all reading my problem and taking the time and effort to respond, especially with photos too in some cases.

Jon - Laser Engines was spot on with the photo and the explanation. That photo together with the relevant ‘arrows’ was just great and the mention about the ‘slow running needle’ extremely helpful. Thank you so much Jon.

Engine Doctor - Thank you also for your photo reference but as you can gather it’s a slightly different carburetor that you’ve shown. Really appreciate your comments though.

Martin Harris - Again the wrong carburetor shown in the photo, but the comment regarding that ‘slow running needle’ was very apt as before writing my question I had inadvertently removed that screw due to its ‘apparent’ relevance to that throttle arm, being in the actual hub of the throttle barrel.

So, once again,Thank you all for your contributions not forgetting Peter Christy and Petrol Pete.
My engine is now running very well and with that throttle arm successfully rotated, more easily connected to the throttle servo.

I feel that I must apologize though for the slow response to your collective helpful comments. I do so most sincerely, but I’ve been quite ill during the intervening period, but I’m back on the road to a full recovery now.

Once again Thank you all for your help, and Happy Flying.

Kind regards,

John.

Martin Harris17/08/2020 12:10:56
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9501 forum posts
256 photos

Reminds me of when a clubmate asked for help as his engine wouldn't give even the slightest pop - I found the low end screw was wound right in and mentioned it to him.

"Yes" he replied, "I noticed that was loose and tightened it up..."

Glad to hear you've recovered from your illness.

Jon - Laser Engines17/08/2020 12:36:36
5621 forum posts
271 photos
Posted by Martin Harris on 17/08/2020 12:10:56:

Reminds me of when a clubmate asked for help as his engine wouldn't give even the slightest pop - I found the low end screw was wound right in and mentioned it to him.

"Yes" he replied, "I noticed that was loose and tightened it up..."

Glad to hear you've recovered from your illness.

I have had a few engines come back that 'wont idle' as the throttle stop screw on the super tigre carb had been tightened up and was jamming the throttle half open

JB, no problem. I had an ASP52 once and it ran nicely. The 61 was good too in my aerotech wayfarer bipe.

Which model are you flying with the engine?

JohnnyB18/08/2020 14:54:21
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262 forum posts
38 photos

Hi Jon, I'm installing the afore mentioned SC52FS in a Seagull Arising Star trainer.

I have several other models that are electric but being a bit of an 'oldie' I'm very nostalgic and I just love hearing an i/c motor in the air. I also have a Chris Foss Uno - Wot with an Enya SS30 2 stroke up front.

I'm getting a bit worried though as the future of i/c motors seems to be getting less and less, certainly regarding new motors.

Being connected with the industry, I really love Laser engines, how do you see the future panning out Jon?

Jon - Laser Engines18/08/2020 16:01:01
5621 forum posts
271 photos
Posted by JohnnyB on 18/08/2020 14:54:21:

Being connected with the industry, I really love Laser engines, how do you see the future panning out Jon?

ummm...my views on that are going to be detailed in an upcoming RCME issue so i best keep my trap shut until after its out! wink 2

JohnnyB19/08/2020 23:19:57
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262 forum posts
38 photos

Thanks Jon. I’ll be reading it then whenever it next drops through my letter box. 😜

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