Hi there. Just recently bought myself a 520 and have had some problems with it from the beginning. Problem no. 1: While driving, or just revving it in neutral, the bike sometimes doesn't go back to idle as it should. I'd say it gets "stuck" about 3 times out of 10. I've had the carb apart and cleaned it. I've checked the throttle cables and adjusted thm. I've checked the valves and they are OK. Tried spraying starter gas around the carb and intake to see if there are any leaks, and nothing happened. So, I'm guessing the jetting needs to be looked and. And no matter how hard I've stared, nothing has gotten better! My current setup: Original exhaust and air filter. OBDTM, clip @ 2nd from top. 175 main jet 52 idle jet 85 starter jet Living and riding at sea level, close to the sea. Temperatures vary between, say, -5°C and 25°C. I've tried adjusting it today, but it didn't really make any sense. Turning it in or out from the standard 2 turns out didn't make any huge differences. Guess I'm just too big of a newb. So, what can I do? I've thought about getting myself a OBDVR needle, since it should improve everything, right? Problem no. 2: While driving along, giving a sudden burst of throttle makes the bike bog down. Now I just read about the O-ring mod a couple of minutes ago, so I'm going to try that. But could it be related to the jetting? I'll add it here in case it helps. Any help would be appreciated!