After getting my dt125 put together from the frame up I got it running. It didn't run good, but after adjusting the carb I was able to get it idling.  I took it outside, put it in gear, and eased off the clutch with plenty of throttle. Except; she bogged out and died. I took it to my road which has a slope and tried again. I rode it all the way down my road, but it was a very slow rpm. I took it back inside my shop to adjust it some more. After an hour of adjusting and frustration I took it back outside. I still had the issue of it dying after the clutch is let out, but if I took it to a slope I could get it to drive. I got on the highway, and the bikes rpm's skyrocket when I switch to 2nd gear. I switch to 3rd gear, but this time it feels like the bike is in neutral and the rpms skyrocket again, then it feels like its surging. I took it back to the shop for more adjustment. The bike bogs out past quarter throttle, and is very smokey. Swapped out the reeds for less used ones, and set my timing. The bike would only run with the choke knob pulled out. Now it starts sometimes for a few moments, and I get a whole lot of backfiring [pops]. I have cleaned the carb before. I pulled my spark plug and it is black.

Congrats on getting it running!

Please define what "put together from the frame up" means to you.

My first thoughts are crank seals, carb oring, timing set incorrectly...

The bike started as nothing but the frame at the start of october. I bought it that way. I bought lots of new parts and got it assembled so I had a dirt bike to ride around on. Ive seen from another post on here that someone bought a pwk28 carb off of a 2001 yz85, so I might go that route and buy one. My carb was filled with the worst corrosion and gunk ive ever seen in a carb before. I do not have a ultrasonic cleaner so I cant clean all the passageways. I have not replaced the crank seals. How much engine teardown is needed to replace them?

I had a very similar situation and it was the timing, it only has to be out a bit and it will backfire, be hard to start and not rev out. 

My wild guess on popping since it wasn't said it was happening at first is battery charge is getting low?

There's a lot going on there by the sounds of things. Not sure where to start. Could be carb, exhaust, crank seal, clutch slip. Only running with choke pulled out points to carb blockage--or lean due to air leak somewhere. Video is always good, albeit a pain to do.

I spent about 6 hours working on it today. I drained the oil and put good oil in. It stopped being so smokey, so I mustve overfilled it when I originally put oil in.

After a few hours of messing with the carb I discovered that if I put my hand mostly over the intake of the carb (im running a pod filter) that it will rev all the way up instead of bogging at any slight touch of the throttle. I threw a freezer bag over my pod filter and I could finally drive in 1st gear.

I did order a pwk28 carb. I will update on results when it gets here in a week. Until then ill continue messing with the stock carb.

It might be a good idea to check crank seals.  Sounds like maybe the clutch side has popped out.

(Overfilling transmission with oil won't make it smoke unless crank seal is not sealing)

Will check the right crank seal soon

I messed around with the carb and it turns out my needle is bent, so that might cause some issues. I ran out of gas and lost my key roughly about an hour apart so right now im stuck until I find it.