Ditto Nathan's post. One other thing to check is to make sure the Crank Case vent is clear. If it is plugged or restricted, you get some dificult tuning problems. One of our guys was trying to get his plane going with an older Mag 52. He had plumbed the vent into a bottle with some cotton in it to keep the oil out of the cowl. It wouldn't hold a steady RPM and had little power. He clipped the line to a couple inches and away it went. Might check this out.

Don