Dt 125lc 1987 back misfires and does not pick up on acceleration

I am going to have you do a series of things to clear up the problem. First come the basics >

Remove the water trap bowl at the bottom of the petcock, (gas valve). Any water or trash in the bowl? Drain a cup of gas from the tank. Any water or trash in the cup? Dump it, clean it and re-mount it, ( not all bikes have a water trap bowl ).

Drain the carburetor. There should be a screw on the lower side of the carb float bowl. Remove the screw then replace it after the fuel drains. Turn the gas back on and wait a minute for the carb to fill with gas. Install a new STOCK spark plug and try to start the engine. If the bike doesn't start and run properly then shut off the gas and remove the carburetor from the engine.

Remove the float bowl and clean the entire carb with a spray carb cleaner from the auto parts store. Wear protective goggles to avoid getting spray in your eyes. Don't be cheap, use a lot of cleaner. Spray into all the little airways and fittings in the carb. Remove the two screws on the outside throat of the carb and spray into the screw holes as well.
< < READ CLOSELY > >
Be sure to put these two screws back in the same hole they came out of. IMPORTANT > do not tighten these two screws down. Only screw these in until they LIGHTLY seat. Now turn each screw one and one half turns outward. Put the rest of the carb back together, clean and dry the air filter and install the carb. Let the float bowl fill then start the engine. Set the idle speed with the idle screw. This process should get you back on the road unless other problems exist. Let's say that the bike is no better >

• How good is your battery?
• Carb, head, intake manifold and carb mounted tight?
• Does the carb intake manifold have reeds? What condition are they in?
• Remove the flywheel cover. Take hold of the flywheel and, without turning the wheel, lift the flywheel up and down then left and right. Any movement or was the flywheel rock solid? If movement then the crank bearings need replaced along with the crank seals.
• Speaking of crank seals, how old are your seals? The bike ain't gonna run with bad seals.
• I don't recall for sure, does the bike have CDI? If so, have the dealer test the CDI and the coil.
• If no CDI, when was the last time the points and condenser were replaced or points filed and set? Get the coil checked.
• How old are the piston and rings? You could have problems there. What shape is the cylinder wall in? Scared up, low spots (you will not see the low spots without running a cylinder hone through the bore).