Replacement tires,seat,motor

I ask in what is this and got some ideas. I was interested in replaceing the tires on my mini bike. It has 4.00-6 and 4.10/350-6. I was interested in just putting the same tires on the front and back. What kind of problems should I worry about? If the back tire will fit inside the forks would there be any issues I'm not aware of? I will need to get a brake on the back it doesn't have one but I was told it did have one from the factory. I'm guessing that is what the bracket is for. There are so many different style of tires also. I figured knobby ones are good for the on/off. I noticed scooter style tires look like good street tires.I'm guessing I doesn't matter? Will
530 X 450 X 6 - Universal Tread size fit? What should I check for fitment? Sorry for all the questions but completely stupid with this stuff. I have a 82 suzuki that I have worked on alot,but this is a bit different. I'm not sure what motor but with a 8 and a 10 year old I think a 3hp should work been looking and harbor freight has them for 99. or bigger for 119. I was wondering about a 49cc or 80 cc bicycle engine at first. I'm not sure it may be to heavy? I was told this is a Cat Slingshot, model R3502. I'm not worried about the seat thinking plywood foam and some vinyl. I dont mind a flat seat and same diameter of wheels. Any input would be helpful. Thanks


I went in to a few stores and found out I can fit 13x5.00-6 tires on the mini bike. the tire just has about 3/8" on either side of the forks. Tires are stuck to the rims. I'm trying liquid wrench on the beads. Going to get the sawz all out next. Any ideas out there? I found the id number is there any way to decode it? 7008625