Need some sage advice and wisdom

[Pete M]

My newly aquired, 2nd SB50p will not accecerate with the air box installed. Once removed it will jump to attention with a bog spot at 90%. It has a new top end, new intake gaskets, crank seals, the cleanest carb you have seen, the needle is in the middle position, new NGK spark plug, new fuel and vacuum lines, 135 psi compression, the bystarter tests good and seems to be working, the muffler was chemically cleaned, The plug will come out wet after a quick run around the block after it is warmed up. It appears to be running rich and the air cleaner just makes it worse. Without the filter in it, it bogs severely. I looked at the main jet and I can't tell if some one drilled it out. What say ye of 2 stroke Spree?

[swimmingfree]

ajust the carb woood be my gusss ...
swimmingfree

[motomech]

I suspect the muffler.
"Chemical cleaning" sounds like it should work, but I never have seem it to be effective.

[odinxxix]

sounds like you answered your own question. it runs rich. with air box off it gets the air it needs to run half way. i would get a replacement jet and put it in and readjust your carb. compare jets and see if the one in your carb is larger then a stock #68?