I am a new biker. I got some tubes to replace, but I am not able to identify the valve, I try to force air with presta convertor but the moment I remove it air blows off in a second. Please help identify valve and suggest how to fill air
I think its worse than that - your valve core is not there, but the thinner thread where you connect the airhose is there.
That tells me the shaft of the valve core broke off, the acorn nut was lost, and the guts of it fell into your tube.
This is what a removable valve core looks like:
Your tube appears to be like the one on the right, with no removable core.
You have the coarser thread as an integral part of the valve stem. Had the valve core been removed, that coarser threadded part would be gone too.
Answer Your tube is dead and need to buy another tube.
The only way to save it is if those two threadded sections can be separated by unthreading the end. And I suspect they won't because I can't see any flats for a wrench/spanner.
Sorry for the bearer of bad news. If you want to find some less expensive tubes, search online resellers like wiggle or chain reaction. Their Lifeline brand tubes are about $4 eurodollarpounds. I buy them in 5 packs and keep them in stock.
You seem to be missing the valve core in your Presta valve. Perhaps you removed it? It is the most important part, it must remain in the valve.
If you no longer have it, you need a new one or a new tube.
We have many questions and answers about using the valve here. You just unscrew the small safety bit on the pin, optionally screw on an adaptor and then you connect the pump.
Agreed. This valve has a removable core, which has been removed.
In this picture, you see the body of the stem in black. The removable core is silver, with screw threads. And the nut is on top of that, with diamond-pattern knurling.
To pump up a Presta valve, loosen the nut and press down momentarily to unstick it; when finished, tighten the nut. There are some pumps that thread on to the valve core (if you're using a Schraeder adapter, this does not apply), and when you remove the pump head, it takes the core with it. This can be frustrating. The solution is to tighten the core into the stem really firmly, and/or use thread-locker. The reason for removable cores is to allow you to inject sealant into the tube. Not all Presta tubes have removable cores, so if this just annoys you, look for ones that don't have them in the future. You can also buy replacement cores, if need be.