125-200cc 07 wr 125 issues

My sons have equally prepped WR 125's , but one rips throught the rev range and one does not. They are both stock and jetted faily close to each other, but the one with the most time on it does not rev out as far, and does not have the bottom end pull.
The one in question also has had the reeds replaced last year and new rings.
This has been a common theme with them preety much since we got them, just not this pronounced.
The bike in question is also ridden by the most aggressive rider.
Where should I start? Carb, reeds or power valve?
Thanks in advance.
By the way, I got to ride the good one this weekend and I now understand what the big deal with the WR 125's is.
I plan on keeping the good one for me when it comes time to replace them!

Did you do a compression check? if yes,what did it read? If no you need to do that first.
Why not jet them exactly the same? if the one bike runs great?
What type of reeds did you put in.?
Maybe timing is different?
Good luck.I'm sure the experts will chime in.

What does Craig say?

Im looking for other options from long time 125 riders. Ill be checking reeds, carb vents, power valve and muffler this weekend.
Compression is good (new rings this year), Ill check jetting in both.
I cant remember what type of reeds went in, but they were not stock.
This bike also had the flywheel come loose twice and broke the woodruf key twice as well.

A shot in the dark... Make sure you have the correct plug (BR9EG). The analog ignition on the WR125 doesn't like non-resistor plugs and it will not run well. Resistor or non-resistor plug will work on a WR250 analog ignition, so people expect the WR125 to be the same.

Thanks Norm, I'll pick up a few and start there. I'ts fast and cheap.
I rode the good one while arrowing the Hixton H/S this weekend and just loved it.
I've always ridden 250's and big bores but this little bike really impresses me. I'm old and broken so ease of ride is more important than power anymore.
I may 144 both of them as soon as cash allows it.

Do the 07's have power valves?

Do a compression check on both. use a quality gauge kit. Do them both the same, decide how you will check compression, and always repeat for every test. I check mine all the time, after a couple hard rides. I check mine warm with gas in the carb and petcok turned off, clean air filter, wide open throtle, pipe and exhaust on, and the long plug adapter in my snap-on kit. I get 225psi on my CR. If I see it drop under 200 I will change the ring.

Thanks! I'll check the compression asap.