I have an older bluebird "lawn comber" with the bagger thing in the back. It has a robin engine on it and you pull the lever along the left side to engage the blades. The height is all messed up so how do i know how far the blades should reach. I used it on my lawn as an experiment raised it as high as i could i think and i ripped up a ton of stuff. I got dirt grass dead and green grass all up. I hit the dirt and it some places tore up the grass and thinned it out it most other places. Is this right or wrong? I was thinking of getting a newer one because i dont think this one goes high enough. How should the lawn look after a proper dethatching job? PS this was a nice thick green lawn.