Sorry I haven't replied in a long while, I stopped checking this post a few weeks back
I never thought about the motor mounts not being level. I am using the stock T-Maxx mounts. It could be possible one side is lower than the other.
I was thinking the problem could be that the fuel was igniting. But, it was just enough not to start the engine but at the same time, just enough to make the bearing feel like is was slipping. Then when I take the engine out, the fuel line is disconnected of-course, and thus the bearing didn't slip.
I haven't tried to start my truck in 4-5 months now but when I do, I'm going to richen the low end needle and see if that helps. I say richen because I know I have it leaned out more than I should.
Will post my result.
Thanks for the replies.