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Throttle Servo Linkage - Is this correct ?

Throttle Servo Linkage - Is this correct ?

Old 05-12-2012, 05:56 AM
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Arrow Throttle Servo Linkage - Is this correct ?

Hi Guys,

Please can you take a look at this video and tell me if the throttle linkage is set correctly to allow sufficient air into the carb ?

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.


I have not tested it yet since I installed the Servox throttle servo but want some advice before I try it. I have left about 2mm open on the carb when the servo is centred on.

Thanks
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Old 05-12-2012, 01:09 PM
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2mm!? Thats WAY too much!

When the servo is idle (when you're not pulling og pushing the throttle) the servo should push the carb all the way in, and then you set the engine idle with the idle screw.
Usually about .7mm gap.

And when on full throttle the carb should be fully opened.
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Old 05-13-2012, 03:26 AM
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Thanks but when I set the carb fully closed and adjust the idle screw, this is not normally enough to start the engine. I normally have to give about half throttle for the engine to start...what could be wrong here ?

Too much air and not enough fuel ? I have the top screw on the carb 3 turns out from closed position.
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Old 05-13-2012, 03:49 AM
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If you have to give it that much throttle, its likely you have the low end needle way off. Either too lean and not enough fuel for the amount of air going in at idle or too rich and not enough air to get it cranked. If you have fuel spewing out the pipe, close the needle some.
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Old 05-13-2012, 05:02 AM
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Yeah, fuel was blowing out of the pipe...I thought this was high speed needle was 3 turns out.

If I totally close the low-end needle and then set the servo linkage so that the carb is closed, how much should I open the low-end ?

The engine is a Force .28...the instructions are fairly basic and do not go into this level of tuning !
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Old 05-13-2012, 08:28 AM
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I would set everything back to factory settings and start again from there. It should start and idle with those settings. Also as mentioned before, it should be pushing the carb closed all the way at nuetral. Your high speed needle only sets your mid-wide open fuel flow. If u have you idle gap and low speed set even just close it should start and idle through the whole tank.
You do not want to close the lsn all the way. You can damage your carb.

The manual for the 28 says the following for "new engines":

HSN - 3 to 3.5 turns from closed- I wouldgo with 3if its been over a gallon.

LSN - flush with carb barrel

The throttle gap should be between .7 and 1mm when the carb is being pushed closed.
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Old 05-13-2012, 02:46 PM
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Sory for thread jacking but i have a similar question. On my buggy when its idleing i get small drops of fuel out of the exhaust tip, is it running too rich? Or by spewing do you mean alot of fuel?
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Old 05-13-2012, 07:57 PM
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By spewing I mean something similar to when a baby learns to make spit bubbles and goes nuts with it, spraying everywhere. A couple of drops is normal, there will always be excess oil coming out the exhaust. To get the best lsn setting, It's said to start at factory setting, then lean by small increments until there isn't a noticeable gain anymore.
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Old 05-13-2012, 08:03 PM
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Originally Posted by deltrum View Post
Yeah, fuel was blowing out of the pipe...I thought this was high speed needle was 3 turns out.

If I totally close the low-end needle and then set the servo linkage so that the carb is closed, how much should I open the low-end ?

The engine is a Force .28...the instructions are fairly basic and do not go into this level of tuning !
The linkage seems to be set up fine on the video. I would do as Kain suggested, start from factory settings on carb.
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Old 05-13-2012, 11:25 PM
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Thanks guys
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