I suspect it's drowning in fuel. But ...
>>eli jos on tulppa irti ja annat huikan
>>ni tuleeko sumuna tai suihkuna tulpanreijästä.
... check this first.
The engine can easily drown in oil / fuel, and then it refuses to start, until dried.
Example: you spin it for 20 seconds without glowplug current, accidentally. It drowns in fuel. Now, even if you put power to the plug, it should start. But it doesn't.
Therefore, I usually don't spin it for longer than 5 seconds.
If it doesn't fire up, I close the fuel clip, and spin for up to maybe 20 seconds without fuel supply. Usually it starts now on the remaining fuel in the carburetor.
If you suspect it has drowned, take out the plug, shake it dry, open the carburetor and spin at full throttle (with closed fuel valve) until no more mist comes out).
Then try to start (for maybe 5 seconds) with fuel clip closed, at idle throttle. Nothing => open fuel clip and try again.
If this doesn't work, I suspect the regulator is broken.
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Try setting around 12 % throttle, that's a typical value from my helis.
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* Tank pressure does not matter at all, it will still idle at zero overpressure.
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* Bearings, very unlikely. They can't be that rotten.
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you have checked for compression, haven't you?