The pass few months taking out the fifty it's starting to take a while before it's starts to get all it's power, around 10-15 minutes. What would cause this? is this a sign the motor has low compression? Basically i guess what i'm wondering is if i should through in a new motor or is there some adjustments i need to make.

 

Could be a few things. If the valves are tight it can cause this. Real easy to adust them on the 50s.

Could be lean. Try raising the needle in the carb 2 spots. This means you need to lower the clip. It will most likely be backfiring until it gets warm if it's lean. More of a Pop.