My engine is completely built from parts (new) I have not had the spun bearing since the lock tile and have new case crank piston, bearings and cylinder replaced ring with a Boman ngk plug rcexl ign. the reeds flat sanded new carb and pulse line. Still have that nasty almost quit on throttle chop needles makes no change. Idle any lower than 2000 becomes unreliable and quits. Timing checked and rechecked at 28 have tried 32- 21 just runs rougher. Used JZ carbon fibre APC form 18x6-19x8 just loads the top end the high idle makes the landing hot and at times safer to kill the ign. I give up! Front bearing is a sealed bearing never had the internal rubber seal like the V2. The case is just to thin heat will distort the case and allow the bearing to spin the cranks are so soft you can write your name on the machine bearing surfaces when they cast the counter weight what ever slag was left in the sand mold stayed there making some of them shakers mine smoothed out when I replaced it. The 50r is worse.