I’m late to the conversation but if you increase your rpm you need to increase your feedrate to match. Your current feedrate is too low which is why you’re burning the material. The key metrics with CAM are surface speed and chipload which are influenced by a combination of the feedrate and spindle speed.
In summary, if you increase spindle rpm and get burning, you’re sitting in one spot too long so increase the feedrate as well.
Here’s an example of some feeds & speeds in Walnut (using the Makita):