The older ones are angled. I have both. The self cleaning valve body is at a right angle to the burner stem. The valve stem on the new version has a little splined end that drives the self cleaning needle into the burner jet when you turn the valve all the way to the right. The needle is set into a little splined brass part that could get gummed up over time, I suppose. If in doubt, you can squirt some carburetor cleaner into the jet body (stove off!!), let it soak, then fire it up. I've never had a problem with either of my Svea's or R8 stoves.