Too Much Compression
Typically engines that have been built with too high a compression ratio will pull very well until they reach their ceiling but they won't fall on their face there - they'll still pull very hard at that rpm, they just won't rev any higher. In that case it's time to grab another gear. All that compression should allow you to grab another gear any time. Keep in mind that 250 psi static compression is very high. The only time I see numbers like that is when I'm below sea level with dry desert air.
If you want to be able to rev the engine out (8200 +) you'll probably find that it doesn't work well for your type of riding. Many motocross riders rarely see the high side of 7500, with 6900 rpm's being more common.
There are a couple of things that prevent an engine from revving. One of them is transfer ports that are too high. Another is jetting that's too lean. Another is power loss due to an over heated engine. Before swapping parts check your set up against your baseline notes to be sure everything is OK. If you've changed your riding style you may have to make some mechanical changes. Since you're a motocross rider I'm thinking you may be running lean on the needle - that just kills anything above it.
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