4 stroking motor?

I am getting a little more used to these engines and I've noticed on my 61 cc at certain times through the throttle posistion the engine comes to life- what I assume is when it is really running like a 2 stroke-cleaner tighter sound, less vibration, and definatly more power! My engine is still being broken in with only one gallon of fuel ran through it so far. I just filled up again and changed the mix to about 26-1. 10 oz of valvoline oil (2stroke of course) to 2 gallons of fuel. I was running at 16-1.Waiting to ride today. The engine does not smoke and the plug seems a nice slightly dark tan color (ngkb6). It progressivly seems to 4 stroke less and less.
My problem is with the new 49cc kit I installed last night on my sons bike. It has the new nt carb and slant head. It does nothing but 4 stroke! I will replace the spark plug today but when i changed it on my 61 I noticed no difference at all so I'm not expecting that to help. The engine will not accelerate under load-riding it. Seems to idle well and when staionary revs out well but will not 2 stroke. Should I just run it for awhile to break it in a bit or start messing with the needle? It also smokes a bit where as the 61 never did. Could it be the oil in it from manufacturing? The engine is such a tight fit I have to remove it to get to the slide on carb (had to drill a hole through the frame to route the throttle cable, steel frame so should be okay?). Just a hassle to get to. Maybe I will get new screws to mount the carb instead of the stud and nut-I dont know how they ever got those nuts on or how I will get them off. It would be alot easier to remove the carb for adjustment than the whole engine!

I lowered the needle on both engines and wow what a difference! They both came alive! Still a little 4 stroking at the very top end but both are reving out far more than they were. Gonna run a few tanks of fuel through them now before I do any more carb adjustments. I will check the plug to make sure I'm not to lean. I will read up on rejetting incase I want to try that after break in. Do you have to replace the needle also after you solder and drill? where do you get the needles if you have to replace them?