Don't you have the instructions..? They're pretty comprehensive on tuning
the SX although we all have our different methods... ;-)
Assuming you don't have the instructions;
Needle with knurled knob next to the fuel inlet is the main needle; Factory
setting is two turns open from fully closed.
Opposite needle that's exactly the same type but set into the carb' a little
more is the mid-range needle; Factory setting is one turn open from fully
Slotheaded***in between the two is the idle needle; Factory setting is
two turns open from fully closed.
IMO; Best to leave the mid-range fully closed just to start with but
otherwise the factory setttings are a reasonable place to start from with a
I set the idle needle with the 'pinch test'; ie. start up, pinch off the
fuel line close to the carb' and if it quits immediately it's too lean,
(indicated by a complete lack of any smoke too), if it speeds up
considerably and runs a few seconds it's too rich, if it speeds up a little
then quits quite quickly that's about right... (Bruce Bennet reckons the SX
likes a 'crackly lean' idle but I find it won't drop 'off the pipe' for an
auto if it's that lean.) When altering the idle needle the instructions
advise moving it at least 90 Deg. in the required direction then back to the
desired position to avoid the throttle barrel movement becoming stiff...
They don't use the pinch test but it seems to work for me... ;-) Use 1/8th
turn movements to start with and drop those down to just a few degrees
when 'zeroing in' on the correct position...
With the mid-range needle shut right off, the engine should still pick-up OK
but if the smoke dies off then open it again up 'cos you don't want to run
it lean from new...!
NB: If you're using a pipe then you have to suffer the engine running really
farting rich just before it 'climbs on to the pipe' or it will go really
lean once 'on the pipe' and burn up..! No such problem with a 'muffler'
and higher Nitro...
Next I'd set the top-end with high power climb outs, dunno whether you're up
to that yet..? If not you want to get some assistance to get it correct;
Tying down to a training stand or using 'headloaders' doesn't, IMO, give
very accurate settings...
If you're using reasonable exhaust pressure then you'll find the main needle
is fairly rich at two turns out so it'll probably be smoking heavily and
kicking the tail; Just lean off the top-end needle a few clicks at a time
until the motor _just_ holds a smooth two-stroke, you don't want it any much
leaner than that for quite a few tanks, if ever...
Then it's back to the mid-range needle at the hover; Again you want a smooth
two stroke just lean from the point it's kicking the tail from 4-stroking
There is hefty interaction from the main needle to the mid-range needle down
to 1/3rd throttle opening but not vice-versa at the top so the top end
needle wants to be correct first...
The idle needle shouldn't ever affect hovering power unless the SX is
stuffed into a 30. ;-) The other two needles effect is cut off quite
sharply at 1/3rd throttle so they don't affect the idle at all & vice versa
Main thing to avoid is the smoke trail dying off and the engine 'sagging'
under load due to overheating either too lean or over loaded ie. over
Suggested settings are a little difficult without pipe length & type, fuel &
plug info' plus RPM you want to run too...
Nick M.V.Salmon... Southwest UK...
>I am trying to set up a OS1sxh with a 60B carb in a Vario Sky Fox - The
>factory settings will alow me to start the motor and it will idle, but
>any attempt to increase revs results in a cut - The motor starts to
>pick up but then cuts dead. I'm not sure if it is rich or lean cut, and
>I'm not sure which of the 3 needles to start adjusting...
>Any one got some settings I could try?
>Take out !!nononospam!! to reply