Okay,

Here it goes. I've got a 1996 XCR600SP with 700cc cylinders from a 1997 machine. This was a complete overhaul of this motor including the carbs from a 1997 machine and the CDI box. After running this machine for about 50 miles or so with fresh gas it seems that the machine idles real high and only runs real good once I get to about 7000RPM. I believe it is the timing but I'm not sure how to check. Anyone have an easy way to check and adjust timing? By the way, when it gets on the pipe it turns into a rocket ship.

take the recoil cover off and the round spool so you can see the stator plate. There is a mark on the outside of the stator. Clockwise rotation is advance. don't go too far with it , like no more than an 1/8 in either direction. I would say advance if anything. It's probably something to do with the low circuit part of the carbs. Those round slides are antiquated.
If you still have the air box on the sled. make sure those carb overflow lines are where they should be. some are meant to be fed in the airbox and some just go down. Find out which way it's supposed to be.
Sound strang? but I had a sled where just one of those lines fell out and it ran like crap till I noticed it. Clean and check your carbs.

Timing should be set at 28 deg. BTDC at 3000 RPM during break in. (if you have the variable CDI from 97 or 98)

this should register 13 deg. BTDC at 6000 RPM

After break in it should be at 29.5 deg. BTDC at 3000 RPM.

to check, use a ferret intrument t84 Variable timing light.

good luck