If you are going to play with it, leave the power cylinder alone. Just look over the control valve and the slave cylinder. If you go into the power cylinder, you may go down the road to end up with parts needed destroyed in teardown that you can't find. The seal and bore in the slave cylinder are most likely gremlins. Also check the vaccum lines and air cleaner lines and filter. I'm going back for more cores, to hell with Jim Carter.
