It is due for a bore job so figured while it was apart I’d have it ported n gain a lil power
If it's stock, that's not too difficult of a build requirement. If it's not, you may need the builder to tell you where things are currently and make recommendations depending on what you want to experience when riding it, your skill level, terrain, budget and capacity for maintenance.
The stock system is very docile by design, so it's easy to improve it. A basic setup for something resembling a CR250R type spec with an OE cyl, the project should include everything in between carburetor and pipe. If not, porting isn't super beneficial, and you can probably get away with reeds, carb and cylinder head design and if budget allows, a pipe. If you go big-bore, a lot of the detailed design is less important because you can rely more on simply adding displacement. The downside to this for me personally is the added vibration. If you do a detailed design on a big-bore you can make a lot of eye-blurring, straight line power, but may require a high budget. Personally, I think the best use of the TRX250R's design is as an MX bike, so is in the relationship between the engine and cornering, and less in raw HP numbers. Riding the edge of stability in a high speed corner and transitions with a properly setup R is one of the best things life has to offer.
Lastly, don't neglect the bottom end's maintenance. Honda designed it very well, but even Japanese bearings wear out and will come apart inside the engine. If you're not sure when this was done last and to what level of quality, it has to be done as the first priority, performance second.
