The KLR250 don't have no stinkin' REV LIMITER, unless you consider the valves, intake and exhaust plumbing as such!
There is NO PHYSICAL CONNECTION between the throttle and the slide of the CVK34 carburetor on your KLR250; the slide is raised by "vacuum" (pressure differential) on the diaphragm. Pulling the throttle "all the way back" only opens the butterfly valve admitting air flow through the carburetor; the slide is raised, as mentioned, by the lower pressure in the venturi, piped above the diaphragm. Atmospheric pressure below the diaphragm actually raised the slide, technically speaking. An air-tight diaphragm seal is necessary for effective carb operation.
A 39 mm carb, likely, is wretchedly oversize for a stock KLR250 engine, in my opinion. A too-big carb reduces intake air velocity to the extent fuel cannot atomize properly, resulting in unsatisfactory combustion.
If I haven't done it before, I commend to you "Carb Overhaul" on page 3 of the, "How To . . . " thread on this website.
Also, while I'm commending stuff, I include, "Care and Feeding of the CVK40;" available from Googling or a "sticky" post on this website.