If i installed a big bore kit in my ex should i have any problmes with it later on???

 

It highly depends on whoever designs the big bore and what parts they use and how good of a mechanic they are.
Lot of variables...

 

Never bore over a 400EX, you will be only looking for trouble. My friend did it and he had nothing but problems after that. If you want more power, get a Predator or Raptor. Don't bore over the 400EX.

 

As with any engine, if you bore it over, you will get more power. More power means more stress on the engine. The more stress on the engine, the faster it will wear out.

That said, as long as you do frequent oil changes, and you don't ride the **** out of it, it will probably last you quite a while. Keep in mind, once you bore it over to about 440, there is no more room to bore it again, and you have to get a new cylinder. Depending on how long you intend to keep it, this may or may not be an issue.