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Diamond Geezer10/11/2007 09:31:00
334 forum posts
8 photos

Hi Guys

me again does anyone know how to set up the bottom end screw on me carb I think this may be part of the problem the troubl is when I screw it in to weaken the mixture cos its too rich the engine won't start again unless I screw it back out cos no fuel is getting up to the carb

Engine Doctor10/11/2007 11:40:00
2536 forum posts
39 photos

Hi Ya . First check that the fuel nipple on the carb is pointing towards the front mounting screw on that side of the engine. If its not loosen the two screws slightly and it will turn easily. If thats correct then connect a clean piece of fuel tubing to the nipple and gentle suck and listen for the air going through the carb . now screw in the slow running screw , with the carb closed until the air stops . Be gentle or you will damage the jet or the screw . . Now undo the screw until you can just draw air through the jet ,this a starting point. The reason for sucking the air is to avoid spit going into the carb and blocking the jet. Now prime and start the engine allow to warm up and adjust for full throttle running .Close the throttle and allow to idle for a few seconds and open the throttle smartly . If the engine diesand sounds like its sucking air then richen the idle mixture by a 1/4 of a turn and repaet . If your engine splutters and smokes and gradually builds up speed then it is too rich . Close the jet (screw in) a 1/4 turn . When you are getting near to the correct mixtuure then adjust the mixture screw by 1/8th or 1/16th of a turn .

Failing that get a mate at your club to show you . Its easy when you get the knack and learn to listen to the engine.


Diamond Geezer10/11/2007 12:27:00
334 forum posts
8 photos

Thx E.d

I'll give it a go

Diamond Geezer10/11/2007 12:48:00
334 forum posts
8 photos

Hi E.D

Does it matter where the main needle jet is at ie should it be closed 3 turns open

Tentpeg10/11/2007 23:41:00
70 forum posts

Here is the basic set up which seems to work for me with any engine.

It is a copy from one of the magazines and I think Steve Dorling knows what he's talking about.


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  1. Charge the tank to about one third full (only).
  2. Open throttle wide and close the main needle completely.
  3. Open main needle three full turns from closed.
  4. Place finger over intake & rotate propeller 6 times.
  5. Remove finger and close throttle to one third open.
  6. Connect glow battery.
  7. Start engine - either by hand or with a starter.
  8. Gently (important) open throttle to flat out setting.
  9. Remove glow clip (with extreme care).
  10. Hold nose of model up at 60 degrees or so with propeller arc well clear.
  11. Close main needle valve until engine rpm’s peak.
  12. Open main needle one or two clicks from absolute peak rpm.

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  1. Close throttle to one quarter (i.e. fast idle)
  2. Open secondary needle one quarter turn.
  3. WAIT for 5 seconds and observe results.
  4. If idle rpm SLOWS, close secondary needle back to where it was.
  5. CLOSE secondary needle, wait five seconds and observe results.
  6. If idle rpm speeds up then you are heading in the right direction – opening or closing the secondary needle slightly until the idle speed peaks is your goal.
  7. Open throttle wide and check response.
  8. If engine hesitates open secondary needle by just a click or two.
  9. If engine splutters and throws fuel droplets from the intake, close the secondary needle by a click or two.
  10. Open throttle wide and recheck the main needle setting with the nose of the model raised.

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Steve Dorling adds, it is good advice from this point on to set the needles on your model and then reset them at the same time as you reset the needles on the vehicle that brought you to the flying field!


Good luck.



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Diamond Geezer11/11/2007 16:28:00
334 forum posts
8 photos
thx for the hlp tentpeg
Engine Doctor12/11/2007 16:42:00
2536 forum posts
39 photos
Hi ya Dia geezer . The main needle should be opened about 2 1/2 turns for starting then adusted with engine running at full throttle to give maximum revs then opened one click so as not to be too lean. then tune the idle needle as described earlier
Diamond Geezer12/11/2007 18:48:00
334 forum posts
8 photos
thx e.d

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