Well I put 30 miles on my rebuilt motor, took it out last weekend when I was home from college took it down the driveway and on the way back up it lost ALL of its power, wouldnt even go 20. Pulled it in the garge, tore apart the carb and cleanded thoroghly. Ran good for 10 minutes now its doing the same thing? I cleaned the tank and put a new filter in during the rebuld. I noticed some black debris in the carb, possibly rubber? Anyone have any idea whats going on!?!

 

is the carb boot breaking down and breaking pieces off and being sucked in the carb?

 

It may be that the inside of your transfere hose from your tank to your carb if it is neoprene replace the hose.The neoprene is breaking down.
Good luck.

 

I put new hoses on, cleaned the takn again and I thought all was fine. Ran good for about 15 minutes then I parked it, got back on and there was now power again. idles and starts fine but no high speed power.