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DLE 20/petrol engines - remove throttle return spring?

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Rich too19/04/2014 17:20:25
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3057 forum posts
1070 photos

I removed the spring on my Zenoah 23 and never had a reliable idle. So, I am now installing a DLE 20 and the instructions say to disconnect the spring tension, which I am reluctant to do.

What do you do?

I tried a Google search and opinion seems very divided.

Why do they bother putting them on, if they then advise disconnecting so that there is no tension? dont know

Rich

 

 

Edited By Rich2 on 19/04/2014 17:21:15

iqon19/04/2014 18:25:27
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1470 forum posts
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My spring is off and works, if you leave it on you are fighting the servowink

don't take it off completely, just unclip it..

Rich too19/04/2014 20:45:11
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3057 forum posts
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Thanks, but why is it on there?

Any other opinions?

Cheers

Rich

iqon19/04/2014 20:50:27
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1470 forum posts
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guessing the carbs are used on other things like lawnmowers, blowers etc....dont know

john stones 119/04/2014 21:01:45
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10839 forum posts
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Yep Walboro carbs on most petrol equipment

no servo's on them wink

Rich too19/04/2014 21:26:54
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3057 forum posts
1070 photos

Mmmmm, thanks guys.

I have read a few threads on other forums and opinion is very divided, however it is agreed that the load on the servo is negligible.

On that basis, and the fact that idle will be more consistent, and the engine will idle in the event of linkage failure - I am going to try with the spring....

Cheers

Rich

Former Member19/04/2014 22:04:02
3578 forum posts

[This posting has been removed]

Ultymate19/04/2014 22:21:24
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1700 forum posts
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You can disconnect the spring but as Tom has said above do not remove it as it will cause the butterfly to vibrate laterally inside the throat of the carb and cause premature wear and poor idle due to air leaks around the butterfly at idle. The load on a servo is negligible, in fact wherever possible I leave the spring connected and just use a thin boden cable to the servo to pull the throttle open and rely totally on the spring to close the throttle, doing so limits the amount of vibration being passed directly to your throttle servo

Ronaldo19/04/2014 22:34:02
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243 forum posts
17 photos

Ok Rich. Agreed there's not a lot of resistance on the spring that a decent metal geared servo can't handle, but I prefer to unclip it, ... cos' ''Resistance is Futile'' ( whoops sorry, couldn't 'resist' adding a bit of Borg lingo wink )

If you do decide you don't want it on, just unclip it from the arm and leave the spring on the throttle arm's shaft. this will take up any play, preventing wear on the shaft caused by vibration when the engine is running, leading to sloppy throttle response and fuel leaking from the throttle arm shaft. I've always found that most throttle arms have a bit of play and can slide in and out freely when the spring is removed completely

I do this with all my petrol engines and have no problems with the idle setting.

Ronaldo

Ronaldo19/04/2014 22:41:20
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243 forum posts
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..... embarrassed and as I forgot to mention as Tom and Ultymate said above , prevents wear on the butterfly.

Thanks guys,

Ronaldo

woody19/04/2014 22:58:56
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114 forum posts
38 photos

I disconnect the spring on all my petrols, but I also use a good quality digital servo, it's surprising how much of a difference a good servo on the throttle makes,

i disconnect the spring as if the servo is fighting it it will draw a lot more current out of the flight battery's, and I've seen servos burnt out because of it

woody

Ultymate20/04/2014 08:30:54
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1700 forum posts
62 photos

Any good servo should cope easily with the load imposed by a throttle spring. If not they have no chance of coping with the loads imposed by flight surfaces in the air and the amp draw is minimal and will be of no consequence if the models properly equipped with adequate batteries.

Adrian Smith 120/04/2014 10:30:17
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2317 forum posts
1102 photos

As an observation my MVVS 50, which has a Walbro carby by the way, the manual expressly says not to do away with the spring otherwise wear will occur as other posters have mentioned and described. As Ultymate says the best option is to put a decent servo and linkage on and take the time to fine tune the throw via the TX, which I find is time well spent for a reliable engine run.

Rich too20/04/2014 11:33:41
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3057 forum posts
1070 photos

Thanks guys. I tend to agree with Ultymate, having read a few threads. The problem with servos appears to stem from the fact that given no resistance, people tend to go for a cheap servo on the throttle (i'm guilty of that in the past), so i'll put a decent servo on there and leave the spring. I have already experienced poor idle on a Zenoah and want to avoid that.

I'll monitor battery usage....

Rich

Mac Duberia25/10/2014 16:12:26
66 forum posts

Hi all,

Just a quick question on a dle35 ra, would I have an issue running the engine if I turned the carb 180 degrees, this is purely because the throttle control rod can have a straight run from the servo arm.

Any thoughts?

Mac

Engine Doctor27/10/2014 11:11:21
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2384 forum posts
29 photos

Do leave the spring on and connected . As already said should the linkage fail then it a fail safe to idle or engine stop . If its removed or disconnected then the butterfly can vibrate causing the spindle to wear in turn causing air air leaks and poor idle . Never had any problems with servos handling the spring pressure either ,just use a decent servo and not mini servo as the vibes will kill the gears in no time . The old 148 or similar are fine for this and hold well without scoffing all the battery power.

Re turning the carb 180 deg . Usually not a problem but do make sure any holes in the insulator or gasket line up you will also have to turn the insulator block as well . Some engines use drillings to allow crankcase pressure to work the diaphragm pump while others have a short length of tubing from a crankcase nipple to the carb . I regularly change mine round without any problems .

Mac Duberia27/10/2014 14:04:36
66 forum posts

Thanks for the reply but can you clarify what the insulator block is...- is it the black block that is between the engine and the carb? so when I undid the two hex screws the whole carb and the black block came off as one and I turned it 180 and screwed it back on.

Engine Doctor27/10/2014 15:01:53
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2384 forum posts
29 photos

That's correct the black plastic spacer is the insulator block .If it stuck to the carb that's fine and all the air passages should line up fine.

Mac Duberia27/10/2014 15:38:32
66 forum posts

Ok thanks for your time and giving me the confidence.

Mac

Andrew Cousins16/11/2016 12:02:49
163 forum posts
20 photos

Guys just been reading through this thread. I am thinking of converting to petrol. One thing I am always concerned with is battery current consumption. I always go to great lengths to ensure free movement of surfaces to reduce drain on the battery.

Now disconnecting the return spring on the throttle makes sense to me. I understand the safety side of it, engine returning to idle if linkage fails but what about large glow engines they don't have return springs. So I have a question.

DO we have any evidence that disconnecting the return spring but leaving it fitted to stop the butterfly valve shaft wear have any performance issues.

Thanks

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