I am a new clarinet player and just bought a new YamahaYCL-450N. According to fingering chart, if You just blow into the clarinet without pressing any keys, it should sound G. In my case, the sound is E. And the rest of the notes sound 2 semi-tones lower, than it should be.
Is anybody knows what is goign on, please?

It's definately a B flat instrument, is it? Are one or more pads stuck down?

Or failing to open matbe?

That's maybe. If only there was an edit facility on this forum

It should be b flat. I checked all pads, Keyes. All of them work fine. I can play any melodies but they sound one tone lower than should be.

That's why it's called a B flat clarinet. A written C sounds Bb etc.
Why the G sounds E could be the upper ring key is not opening with all fingers & thumb off. You are taking your thumb off for the G?

Checked again all Keyes, pads,springs-OK. Still sounds E without pressing any Keyes.

Two semitones lower than concert pitch is correct for a B flat instrument, if you are using the names of the concert pitch notes as your reference. So what is labelled G will come out as F. That's correct. But as you say it comes out as E, while all the other notes come out correctly, so that must mean that only the G note is wrong on the instrument. Look at the thumb on the left hand as you hold the clarinet - is it pressing on the key/covering the hole? If so take it off and see if that helps.

No, as I mentioned before, all Keyes sound two semitones lower.

This discussion is becoming difficult to understand. You originally said that all the notes play two notes lower than they are supposed to. What do you think they are supposed to do? They are supposed to play two semitones lower than concert pitch, like I told you. It's a transposing instrument whose music has to be written two semitones higher than concert for it to work out in an orchestra. Your other statement was that the G (concert) is comiong out not as F (like I've told you it should do) but as E. This might be because you are accidentally closing the F hole with the thumb of your left hand. Is this tyhe case or not because I'm rapidly losing patience with you.

Sorry to drive You crazy. I am new in this field and may not understand some terms. I just wanted to say that I got fingering chart for B flat clarinet from the internet and try to get the correct sounds. So according to the chart if You don't press any Keyes the sound should be G. I compare it with 440hz tuned piano and it sounds E( two semitones below). The same happened to the rest of the notes. Is that right for B flat clarinet?
Thank You for Your patience.

But 2 semitones below G is F not E.

All notes sounding 2 semitones lower than written is correct.

Here here. That's right. You really must stick to what you originally said Vadimir or we can't understand you. Just to say it again, two semitones down is F. Now you are saying the erroneous note is an F but at first you said it was an E. I agree, it's what all M flat instruments do.

That's B flat of course. If only we had an edit facility

Thank You very much Guys for being so patient with me. It was my mistake. Now , it is clear for me. Sorry, it took me a while)
All the best, stay well.