Lawn mower dies when blades are engaged
Rather than bypassing the various safety systems, either replace it (23 years is not an unreasonable retirement age for a mower) or have it properly repaired (since your "repair" methods don't appear to be oriented that way, take it to somone who is oriented that way.) Rendering the safety systems inoperable is a good way to find out why they were installed in the first place. Perhaps you'll have a child mowing the lawn someday with your customized mower...