It sounds as if something is a bit off. Try the easiest thing first, the spark plug, replace it with a new one. A new spark plug can make a world of difference.
By the way, I looked at the picture of your bike in your profile and I have the same year and color. First year for the A-35 engine although the A-3 engine was still used on a lot of bikes that year too. Tecnically your bike is probably a Tomos Bullet TT, check the stickers.