[Ghostt]

No reason to rev it that high, it's well outside the power band, so your just making noise and could possibly damage the engine.

As far as I know there is no rev limiter the CDI is old technology, it just doesn't know what to do at those high revs

The EX-250's CDI uses a very simple advance curve: 2-dimensions, X and Y, with no compensation for load. It's pre-historic, rudimentary.

At about 4,000 or 4,200 rpm, depending on the year-model of the EX-250, the CDI has the ignition timing at full advance (38 degrees BTDC for the older engines or 42 degrees BTDC for the newer engines).

When you roll-on full throttle at about 4,000 rpm you suddenly make the air/fuel ratio much richer. In a modern car or motorcycle engine the ECU knows when this happens and it retards the ignition a bit because richer air/fuel ratios burn faster than leaner mixtures.

Because the EX-250 CDI has no way to compensate for the sudden rich (faster burning) mixture the ignition advance stays way up there at 38 or 42 degrees and you end up with too much of the burn occurring before the cylinder reaches TDC.

Instead of instantly making a lot more power (as you're anticipating when you open the throttle wide) you make only a little bit more. And the engine slowly lifts itself out of the situation.