Hi
I use a 105mm "kit" from JBS, the piston/liner are very good
http://husaberg.org/mechanical/11677-jbs-700-kit-welded-80mm-crank.htmlproblem now is getting in touch with them seems to be near impossible for the last couple of years.the liner is made by westwood in the UK and the piston is a custom CP
DCR racing in the UK also do a kit with the alloy liner with an RC8 piston i think about 103.6mm but i never read anything about it other than its availability
travis at thumperacing in the us has done some bergs id ask him if he can do an oversize iron liner/ piston and get it together to match one of his stage 5 cams with oversize KW valves.
but the stock cam is very good, good peak power and good peak torque just a little lumpy in delivery, other available grinds smooth things out but loose either torque or power unless you up the cr. there is a Wossner ktm 540 piston that will fit that reduces the head volume by 10.5cc... cr should be about about 13.75:1 , haven't tried it. wossner 8583D. there are also aftermarket pistons that are copies of the OEM, by pro-x and wossner. prox is the cheapest ill get the part number lateron.
the akro headers try to be the same length, the oem ones are different lengths.
the stock 08 engine is really really good and the most reliable of all the older bikes. take off teh ignition cover and check the crank endfloat is at least 0.5mm and if inside use NTN roller mains instead of SKFs,
http://husaberg.org/mechanical/17170-definative-main-bearing-thread.html
porting and oversize valves smooth it out a bit, can use anything designed to fit in the KTM rfs heads .. KW oversize valves, ktm rfs cams fit if you cut the waterpump shaft off. can use sintered iron valve guides from a KTM 450, I got mine from Dave hopkins (DJH) on ktmtalk.
sometimes the single valvesprings break , KTM dual valve springs are the cheapest, kibblewhites are the best
http://husaberg.org/mechanical/10680-all-about-valve-springs-nice-pics.html some people have the cam follower bearings go at 2-300hrs others get 500 hours out of them, the ktm part number is 590 36 061 090
gearbox circlips are a weakpoint, use kawasaki part no 92033-1089 instead, 5pcs
FWIW When I put the akro silencer on the stock engine it lost bottom end but the bigger bore loves it.
stock jetting is a bit lame but you should have the EKR needle as stock which is a pretty good needle, best thing I found is to set the main air jet at roughly the same size or slightly bigger than the main jet, the rest is just fiddling till you are happy.
carbkie.html, Keihin FCR Carb Tuning Procedures
edit; can bore the carb to 43.5mm as well, there are billet carb centre pieces available for this from Thumperaccing in the US
Have fun
cheers
Bushie