I just went through this exact same issue with an early H30 I just completed a rebuild on. When I re-assembled it, I found my guides were good, but the I had the same issue. All the exhaust valves I ordered were .2435 which was real sloppy. I finally found a .245 stem valve which helped but seemed too loose yet. after speaking with Markus, I went with it and have had no issue with the motor. Starts on fist pull and runs good. No issues. I'd run it. Consider how hot that valve gets while running, it needs room to grow...