the rear Jerry, ive developed an ear for bad bearings, the wizzing sound i can hear when it first starts, pulled the cylinder and rear cover and i was right, wiggled the crank and i could see the play in the rear so i pulled it and sure enough, glad i got it before it started distributing metal shavings, have new ones comming, i dont know why it went, i had about 4-5 gallons thru it and i use powermaster 15% with half castor as oil and run it dry each session and pump it full of aro and didnt want to wait on shipping to horizon because i can do it myself in 1/4 the time. i like flying, not waiting on repairs