I finally dug out the 29X I bought in the mid 70s and pulled the needle valve assembly out. It does indeed have a constant diameter, about an eighth of an inch. It may look like there's not much room for air to get through the venturi insert, but trust me, it does. The 29X produces a good amount of power, even with the restrictor in place. With the restrictor out and pressure fuel feed, it really hauls. In fact, I was flying one that way at an Amarillo contest on a Demon and was asked if it was a 36X. Have fun with yours!

Bob in NEPA

I added 4 .005 head gaskets and ran 6 Oz's of 5% GMA through it in a 4 stroke just on the edge of a 2 stroke to finish breaking it in , it loosened up really nice . I think I am going to run another tank thru it and then see where the compression is going to end up for sport flying. Larry Scarinzi says this engine will last forever on low nitro, its really built to take some serious abuse. T.J.