Carby exhaust? ??

[WINDY CITY BOB]

I put the 2 foot piece of copper pipe on the end. The end of my customize stock Muffler, all I did was weld. A pipe between where the Weld had broken off roke on the pipe that attaches to the engine to the stock Muffler. Ending at the rear sprocket. Immediately I drove it a block pulled in the clutch and its screen the highest RPMs I had never heard as fast as I ever heard, I figured carburetors air leak so I simply changed out the entire card to one of my other three times all the same NT Carbs. So I filled it up with some JB Weld because I strip the threads on the nut that goes into the top of the carb. Because i have 3 NT.carbacould it be the two foot copper pipe on the end of the muffler causing this I have used this method in the past smearing J-B Weld all around the curb where any air leaks could possibly be and it does come right off once you detach the carb should I try that again or just remove the copper pipe? Easy thing is to just remove the copper pipe. I just wanted somebody else's input on this.
Thank you in advance. Sorry for all the typos I got sauaage fingers. Voice recognition is not the best
W.C.B.