My bike had been having a radiator problem. Coolant wasn't sucking back into it as it cooled down. I thought it was the cap, so I replaced it, but that didn't fix it. I noticed a tiny coolant leak at the base of the cylinder and realized it was the o-ring that was leaking. This was Friday night (and I must ride Sunday!) Saturday morning I started rounding up the parts to fix it: new head gasket, base gasket and an o-ring. Everything but the base gasket was available. I was able to locate a YZ base gasket about 60 miles away. (Good excuse for a fast road trip on my street bike.) Different part number but it would work. I was told that the YZ gasket increases compression because it's a little thinner and I'd have to run with YZ timing to deal with that. I was already running YZ timing so I figured "no problem". More compression equals more power, right? Well, it sure did feel like it had more power! Admittedly, conditions on Sunday were nearly ideal due to a cold front that had dropped the humidity and it wasn't too hot. But it ran very strong--better than it ever has as far as I can tell. Is it my imagination or could the YZ gasket truly be enhancing performance? (I thought WRs and YZs both had a 12.5:1 compression ratio.) If I'd have known about this, I would have replaced the gasket long ago. BTW, the new o-ring fixed the radiator problem.