I disassembled my bmx for a maintenance cleaning & in the process I have miss placed my non-drive Side spacer!!im hoping to find it but If I don’t find it, would it be okay to part back the bottom bracket without it.???
Im aware the bearings without some protection from elements will damage them.
If I use it without NDS spacer will it be okay for short time use till new bracket kits arrives ????

You should be okay for a short time. Short, and depending on the road condition like dusty, grit and wet levels you encounter.
big problem is without the keyed washer-spacer, it will be harder to tighten the BB without causing other probs.

On another note, can anyone point me to a video on how to install a threaded (Euro) BMX BB? I have a GT Mach One and the BB ois toast. I bought an Oddessey as a replacement and I don't know how to space the inner sleeve including washers. When done there was 3-4 mm of play in the crank. I don't want that.

Thanks

Some brands like Odyssey dont even include a drive side dust cover with their bottom brackets because they claim by design, having the sprocket as close to the bb shell as possible will give the most optimal chain alignment. I asked them because when I ordered a bottom bracket from them they said I wasnt missing it. So you should be good to ride without it!

You will have no issue at all. The dust cover is just that, a dust cover. I have rode for 20+ years and never used one. The reason I never used one was because of chain alignment which is what’s important. The spacers help with that alignment. And also help keep your crank arm from knocking into your rear bottom tubes when you pedal.

Yep yep, all good. thanks