Top end rebuild. Big bore?

[saunabad]

Hello

Background: Seeping a bit of oil between cylinder and block after ridden hard so cylinder is coming off in couple of months when the snow comes. Might have some blowby also since I feel it keeps pushing too much oil from the breather even though I've been pretty careful not to overfill. Have not checked compression pressure yet.

I had the head off couple of years ago to replace and helicoil broken exhaust manifold stud. Cam seemed pretty good, exhaust valves were showing some marks but I just lapped them at that time. Piston had some marking, can't recall exactly, might have been II, so second oversize maybe? Anyway, looking to refresh the thing while it's off.

I'm looking at this kit since it comes with most of the stuff necessary and they can supply valves and valve guides also : http://www.gw-racing-parts.de/index2.ph ... 004&lan=en

* 97mm bore worth it?
* stage II cam worth it?
* Bigger valves worth it?
* Some combination of those? Maybe stage II cam together with standard oversize instead of 97mm bore to keep some meat in the cylinder for future?
* Something I should be prepared to do with carburation if going with hotter cam etc? Running stock airbox and stock exhaust (with some aluminium muffler from Hayabusa or something).

Not really looking to make a ton more power, but of course a little bit more pep would be nice. I ride the bike everywhere, mostly longer trips on tarmac + commuting and some gravel + light trails, so hoping to keep nicely streetable and reliable.

[xtrider]

Save the money on the cam if your not going with a good exhaust and intake mods unless you are going with better carbs. You'll get the best power for your money by going with higher compression 97mm piston(10 or 10.5:1 is reliable), mild porting to clean up the casting and polish the exhaust side. If you go with a bigger cam , bigger valves you turn it into a topend motor , keeping the stock cam (or "stage 1" max) along with the stock carbs and a bump in compression makes these a nice torque bike. I built one with 12:1 compression 100mm piston and ported with a special swirl pattern but left stock cam and headers with aftermarket muffler, that motor has considerable lowend , easily pulls 5th while geared so it's @3200rpms at 60mph ,pops the front up in the air with just a slight blip of the throttle , not more than 1/4 , 1/2 throttle will flip it right over, topend is pretty good but I know it could be better with good carbs and cam, but will loose some of that lowend. It gets hot during the summer though ,needs and oil cooler. I made my other bike closer to stock , 96mm and 10:1 with just a quick porting cleanup , helped it quite a bit but not as much as the bigger cc and higher compression .



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