The last two times out I've noticed a new tick in the engine, and it was louder today than it was the previous time out. I'm not sure what to think of it. The engine is a 2000 with out a lot of hours (it is a replacement for my original '99 engine). First, when the bike is running in gear a growling sound is faint, but it can be noticed at lower RPM. It sounds kind of like loose gears, except it's dependent on the RPM of the engine and not what gear I'm in. When the engine revs, the exhaust noise completely masks this noise, or it goes away, I can't tell. It also does it when I'm just easily accelerating, holding my speed, or I let off the throttle, If I open the throttle fully, I don't notice the noise as much. A tick noise is VERY evident though when I go to slow down and I pull the clutch in. If I engine brake, things sound close to normal, but if I pull the clutch in... TICK TICK TICK TICK TICK. And it is more of a tick sound than a growl when I do this. Don't know if it matters, but I noticed the growling noise more on the left side of the engine the other day when I took the bike out, but I didn't notice it much today. Also, the growl noise was under load, where as the tick noise is not. Back to the tick...when I got home today I got the stethoscope out and poked around the engine while it was up on a stand running in different gears. The noise is 95% under the center of the clutch cover. When the clutch is fully engaged, it's fairly quite, but as soon as I start to slip the clutch, the noise gets VERY pronounced. The other key piece of info is that as soon as chain stops moving, the noise stops. As with the "growl" this tick is independent of what gear I'm in. The clutch works fine as far as not slipping when it's not supposed to. I'm sure I'm going to have to start tearing pieces off the engine to find the problem, but I can't think of what I should be looking for. Any ideas? It only ticks when the bike is moving, and there's little or no load on the clutch. If the clutch is engaged, I can be accelerating, decelerating, or holding my speed, and I don't seem to hear it, but when I pull in the clutch and drop the RPM down to idle it ticks away. Any help would be greatly appreciated!