Easier or harder to start? (This is really like to know) - depends on how well you tune it. Higher compression will be harder to kick and slower revving on the electric start. Most big bore kits increase compression ratio. Just the bigger piston, even at the same CR, will kick a bit harder.
More response? - depends on how well you tune it.
Lesser gas mileage? - depends on how well you tune it and ride it. Generally, yes: more power = more gas.
Bigger dick? - How much of a dick you are is independent of engine displacement..
Hotter running? - depends on how well you tune it. Generally yes: more power = more heat.
Difficultly tuning? - depends on what you call "difficult" and what other mods you do. Power increase from big bore kits is roughly proportional to displacement increase. An 836 kit should give around 12% power increase. It's common to also install a hotter cam plus intake and/or exhaust mods when doing a big bore kit. You will want to check mixture at minimum: if it's showing way out then you need to correct it or deal with carboned up plugs (too rich) or overheating with possible seizing and even burned through pistons (too lean). If it runs like crap, ditto.
