One thing to watch for on 48's and 52's is exhaust valve clearance. If set to tight it will run ok on the ground but when airborn it will heat up more and become too tight and lose power, or quit altogether. I've had this happen to me with two 48's and also a 52. The book says to set them to .004 to .010 mm and this is fine for intake but the exhaust needs to be set more towards the .010 side to accomadate the heat when it starts to work a little. many people think that the smaller setting is optimum and strive for .004 and have trouble with stoppage and deadsticks when a few mm's more clearance will fix it.