At 170 pounds you are CERTAINLY not too heavy. I weigh about 170 - 175 and I almost never get any popping and when I did, the belt had loosened. The limiting factor on my hill climbing is always whether I can push the pedals any more.
Turn the bike upside down, and look at where the securing hex screw is in relation to the slot in the frame housing. If it is as far towards the rear of the bike as it can go the belt can not adjust any tighter. I suspect it will not be there and you will have more adjustment possible. If so, loosen the bolt that secures the rotatable bottom bracket. Using the hex key still engaged in the securing bolt, force the eccentric BB bearing around towards the rear of the bike. This will tighten the belt. If you find the unit doesn't want to move, you can tap it around by striking the securing bolt GENTLY with a hammer in a tangential direction towards the rear. You will be able to see whether you have used up all of the adjustment because the securing bolt moves in the slot. Remember that you are moving it rearwards for tightening and forwards for loosening the belt. When you are happy with the adjustment, secure the position by tightening the hex screw. Some owners of Strda type copies have overtightened and stripped the threads, so be careful, BUT the bolt does need to be reasonably tight or the adjustment will slip. Just don't apply gorilla like force to it.
Don't make the belt too tight, or you will be wasting energy and wearing the bearings more than necessary. Mine is about right and at the position of the front end of the rear fender, a moderate finger pressure on the belt with my index finger will depress it to within about 5mm of the lower frame tube. To make it touch the tube, I need to press pretty hard with that single finger.
Also - until you have fixed the problem, avoid riding it. The popping is rough on the belt and pulley.
I'm assuming in the above that the bike is new and we are not dealing with a worn out belt or pulley.
Last edited by EvilV; 04-01-09 at 03:32 AM.