I would recommend looking on YouTube for tuning videos on the OS 105.
There are a lot of them.
Also, OS Engines has all their manual online:
But, if you have a gov on the heli, make sure you have the correct gear ratio entered into the gov and that the gov is detecting the magnets.
If the gov is working working as expected, then you can focus on the needles
I don't use the OS engines.
I use YS 120SR-X (Trex 700N with 3-bladed head) and 60SR (Trex 600N DFC).
Fundamentally, they use similar "3 needle" carburetors.
There is an idle needle, a hover (mid-range) needle and a high speed needle.
Start with the OS factory recommended needle settings on all three needles.
The way to do that is to turn the hover and the high speed needles CW until they are seated (fully closed / lean). Then turn the needles CCW (open / richer) until you are at the factory recommended settings (EG: 2 turns).
Turn the needles CW = leaner
Turn the needles CCW = richer
Be careful not to adjust the idle needle too much. If you need to adjust the idle needle, adjust it no more than 1/4 turn CW or CCW.
The OS 105HZ-R uses "crankcase pressure" to pressurize the fuel tank.
Make sure the 1-way valve is connected in the correct orientation so that pressure flows from the engine into the tank.
If you blow in on correct side of the 1-way valve, it should allow air to flow through.
Make sure the tank is nicely sealed. If there are air leaks or fuel leaks, make sure to correct them before you try to setup the engine.
Start with the idle first.
I adjust the idle with the main & tail blades removed.
This allows me to validate the gov function, fuel tank pressurization and servo operation without worrying too much about total destruction of the heli if something is not right.
BTW: At some point, you will have a "hot start".
This is where you accidentally have something not set correctly, and the engine starts and wide-open throttle.
DO NOT TRY TO DEBUG THE SITUATION!!!
The fastest, most reliable way to kill the engine quickly plug the exhaust port on the end of the pipe.
Use your thumb over the exhaust port of the muffler / pipe or squeeze the rubber stinger closed and seal it.
This will kill the motor without harm and it does it quickly.
If you forgot to turn on the radio, or the linkage is broken or the servo is dead or whatever - just plug the exhaust and the engine will die.
Adjust the throttle barrel's opening and the idle needle until you get a good, reliable idle.
When you think it is set correct, pinch the fuel line closed. The engine should speed up slightly and then die.
Now, try to hover.
It may be too rich to idle. In that case, lean the high speed needle 2 or 3 clicks and then try to hover again.
Repeat until it hovers reliably.
Once this is working for you, test a full throttle climb out from a hover.
If the engine bogs and there is a lot of smoke, land and lean the high speed needle two more clicks.
Do not get too lean.
I believe the leanest you could set the high speed needle is around 1 full turn open
The hover needle is mainly for the engine's transition from idle to high speed.
If the engine coughs, stumbles or dies in the transition from idle to high speed, the hover needle to too rich.
Lean it 2 or 3 clicks
The engine should always be checked with your finger on the backplate. If it is getting really hot, then enrichen the mixture on the HS needle one or two clicks.
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