Looking into my new (used of course) '96 XR600R.....planning on putting in a new topend to freshen it. Checking the valves before I tear it apart and they were ALL too tight, which doesn't surprise me because of who I bought it from (old guy, only owned it a month, fix and flip type deal). Anyway, I got it cheap enough and I'm not afraid of what he's done to it. I'm trying to get my mind around how this head works. I've become intimately familiar with YZF heads, and understand their workings with the decompression and all. Now, looking at this one, I'm not sure of it yet. I did a compression test on it: 5,000' elevation, 30 degrees, throttle full open, kick kick kick. Only showed ~50 psi. The book says 70 +/- 14.2 (not sure what it should be for 5k, but that seems about right) IF the decompression is effected. What does this mean? Without the decompression effected, it should be upwards of 200 psi, and I can't imagine the thing would even start with that much of a compression deficit (it did start and move under its own power). Thanks in advance for the help!!!