Mike,

It's been a while since I put my Venture together but I recall a similar problem. The local heli expert caught it when he was prepping to test fly my Venture.

Seems like the illustrations in the assembly manual were somewhat confusing, or just plain wrong. As a result I had installed my engine mount upside down thereby positioning the engine too high and causing top of the clutch assembly to drag against the top inside surface of the clutch bell. This resulted in an "almost always engaged" clutch. Sounds similar to what you're describing.

Try flipping the motor mount around. You should end up with the bottom of the clutch assembly almost flush with, or slightly below, the bottom of the clutch bell. When I look at mine from the side I see about 1/16 of clutch assembly below the edge of the bell.

Hope this fixes it!