I have a 1974 dt125 and it dosent want to start. It was running perfect for a while and I parked it for the night, the next morning it started but had barely any power, I kept riding and eventually it just died and would not start again so I pushed it home. I cleaned the carb and inspected the reeds, they seemed fine so I put them back on, checked for spark and it was nice and blue, cleaned the points but nothing worked, yesterday I replaced the coil and it idled for a while, and today i got the gas tank back on and it won’t idle anymore, I can get it to run but only for a few seconds while giving it throttle until it backfires and dies, the spark plug is wet every time I take it out. I don’t know what to do anymore it ran perfect one day and the next morning ran horrible then died

Maybe the needle and seat is leaking by flooding it.

Has your exhaust been cleaned out ,? since you got it,

Start with the basics.
Is the plug good?
is the gap set on the plug?. Daft as that sounds i have been the victim of that one in the past on brand new RD 250.
Is the fuel fresh?
When you changed the coil,did you fit a new cap and wire?
Check the earth points are okay.
Stick with it and you will find it .
Regards Ted

Sorry for the replying so late, but I changed spark plugs and gapped it correctly, I tried the coil woth different wires and caps, it has fresh fuel and oil. The exhaust is from an at1 or something like that, it is not a original pipe but is clear from what I can tell and I changed the carb to the original one but it didn’t help. I took off the engine and I’m going to replace all the seals, if that doesn’t work the only other thing i can think of is maybe the timings off a little. I don’t know what would make a motorcycle stop running after parking it for 1 night

Also when it died I could get it running but the rpms feel like they wouldn’t go past a certain point and then it would just sputter pop and backfire then die

Hi, hate it when that happens. Have you inspected the air filter? Mine had sat for so long that the foam filter material was turning to powder. It would start and run at low rpm, but stall when i gave it some gas.....pulled the air box cover and pulled it out, cleaned the carb again and the bike would run and rev up without stalling. Replaced the filter, did a little air screw adjustment and it was fine. Good luck.

I never had an air filter in the bike but it ran perfect without one so I never cared to get one, the reeds were bent very slightly maybe that’s the problem, normally I could diagnose and fix the problem easily but this one has me stuck

Ok, it's pushed out a crank seal either left or right. Guessing of course but symptoms will be all gaspy & little or no proper throttle response as it's partly escaped, then zero response when it's fully escaped. If it's the right side seal then it will smoke the village out. If the left seal it'll just go all hollow in power--like it needs lots of choke to keep going. That's my guess for the morning.

Not starting after overnight sounds like what happened to me a zillion times as a kid... petcock not off or leaking and badly flooded engine. It can be very difficult to start after that and hydraulic pressure could have popped out a seal...

How it ran not revving sounds consistent with being loaded up too... especially if it sounded "dull" or "flat".