so im trying to get my 300ex to have a bit more pace if I bored it how big should I go so I don't blow the engine and where could I get it done also what other options do I have to crank up the speed.

 

The cheap way is go up a tooth count on the front sprocket. It will slower on acceration but go faster on level packed ground.

 

I was looking for acceleration and top end

 

What mods, if any, do you currently have?

 

Currently as far as i know only an after market exhaust

 

I,d try the higher duration hot cam, but its like $140. Hot Cam Perf. Camshaft TRX250X / 300EX

 

You can go with a big bore, bump the compression up, run a different cam, upgrade the air filter, and rejet. That will give you the power to pull taller gearing if you want more top end. It may accelerate a bit faster even with taller gearing. The downside is after all that the stock suspension will likely become the weak point and that can be spendy to upgrade as well. My usual advice is to look at how much you are willing to spend on upgrades, and then weigh that against selling the 300 to purchase a bigger machine. The 300 is a great machine in its' own right, but if you want to get a serious bump in power it can often be more cost effective to start over with a 400 or even open class machine.

 

And anything else starts sacrificing the bulletproof reliability a lot more.