I have a Sears stationary exercise bike from the 1970s. I has not been used for many years but is in good shape. We were going to the gym for exercise about 5 days a week before Covid19 but won't for at least a year so I thought I would resurrect this old bike. My wife is thinking about getting a treadmill but she suggested we try this first since we have it, it takes up less space, and cost will be less. Also she has a weak knee that operates better on a bike than on a treadmill. One of the reasons that we stopped using it is because it does not have a good motion. The resistance is felt pads and there is no flywheel so pedaling is choppy at almost any resistance. I would like to add a flywheel effect to this bike to add momentum and overcome the choppy ride. The front wheel is 20 inches diameter with spokes and removable plastic spoke covers. I know that adding weights near the rims will create a flywheel effect. I have not been able to find any such weights online. From search results it appears that 30 to 60 pounds is the usual flywheel weight on bikes that have them. I think 30 should be enough here. Any suggestions?

My bike started a weird thing yesterday. Reoccurred today. when peddling normally, there is a noise and a feeling as if a bear is moving up one or down one. i look at the grass and I see I’m in the middle gear at the front sprocket and I’m in the 4th gear at the back. I keep peddling and the “gear jump” happens again.....yet I’m remaining in the same gear, still in 4th. keep peddling some more, same thing. Feels like a gear change/jump, but I remain in the exact same gear. whats going on?