I think you'll be surprised with how much torque a properly tuned engine and a properly geared bike will make. Granted, I am only 185lb but my 69lb bike with the 66cc 2 stroke, 44 tooth rear sprocket will climb hills (paved, lol) at WOT doing about 23-26 mph. So, it's pretty easy to get these things rolling.
Just don't do what I did: get burnt out when something isn't working. My bike was down about about 8 months because I was pissed at it. lol Once I finally got to working on it again, I forgot how much fun it was to ride it.
If you do it right, you won't regret it! Well, 'cept maybe the constant lawn mower smell.
Welcome to the Forum!