Thread: CT90 question

I have a 1969 CT90K1 that I rescued years ago that was chained to a light pole. I start it a couple of times a year, keep fairly fresh gas in it (with stabilizer in the gas), and drain the carb. I don't remember when I rode it last or what its performance was like when I did. I rode it for about 10 miles or more yesterday. It sputtered a bit when the throttle was wide open, but other than that, seem to run alright on flat ground. Anytime we would go up a hill in the road, it would struggle to get up the hill. I would have to downshift to first or second and my speed went from about 40 to 10 or 15 mph, with the throttle wide open. Even on flat ground, it seemed to be a little underpowered. I do have the high/low gear lever set to high. Sometime years ago, I had the cylinder bored and put in a new piston (maybe because I thought it was sluggish, but I don't remember for sure). I don't know if I ever checked the valves, but I think I did set the timing statically. I assume that I did all that correctly. Any advice on the power issue? Just wondering if these are normally a little sluggish and underpowered?