Join Date: Feb 2015
Location: southern oregon
yes. those machines are engineered to provide the best power balanced with reliability possible. every component on the machine is designed for the factory 36ish hp. when you start bumping that up, even more so for you riding on pavement (those machines rely on the slip of the dirt to keep from breaking things like axles) . every bit of power you add adds a stress somewhere and decreases reliability and then compound the issue with riding on pavement.
as to how it feels i have not had a big bore that was not polished in a yfz i had a stock warrior and a stock warrior with a big bore jug and it had a little more right off of the bottom but other than that not much difference. ported with a stock bore compared to bone stock is a noticeable difference but i have never had a ported bike with just a big bore. ported, polished, big bore and stroker crank it is not even the same machine.
you dont "need" the big bore kit. if you get it jetted correctly you will see a significant increase in power just from the porting. the bore itself will last every bit as long as the factory bore. the coating are the same thickness so wear is not the issue heat is the issue ( head gaskets, warping etc.) and as long as you keep an eye on that you will be fine. if it was me i would do the big bore, you will get a little more power for free since the big bore jug and piston is about the same price as stock and with the porting you will need to retune it anyway so might as well.
if you are using this thing to commute you may run into an issue with fuel, the porting alone is going to have an impact on how far you can go on a tank of fuel and the big bore will compound that.
you will need to keep a close eye on the chain, sprockets and axle, like i said theses things were not designed for pavement and depending on how well its tuned and the option you will be adding up to 15ish rwhp.