is this 7 or 8 threads now? jeez
get your engine to run good before you go on modding it.
order a tusk flywheel puller, a tusk flywheel holder and a tusk engine oil seal kit
www.rockymountainatvmc.com has everything you need
order a leak down tester from member Awk08 (or you can build your own, DIY in the DIY section)
leak test before you tear down. then replace the crank seals. pretty easy, except they are hard to pull out, at least mine were.
once you get those seals in, you can leak test again. then pull the topend off
post some CLEAR pictures of your bore (cylinder) so we can judge if scratches are bad enough to need a bore.
we cannot know if your bore is out of round, so maybe try going to your local shop and ask them to measure it
I suggest you order a new piston and rings and get it bored either way. but you need to know the size first. ask the shop what size they recommend or what size the cylinder is itself. order a piston the next size up and give the shop the cylinder and new piston (they need piston to match size)
order new OEM or Cometic base and head gaskets for the cylinder
if you got the $$ ($60 for the bore, ~$120 for piston and shipping) i say send your cylinder and head straight to KOR and he will measure and order you the right size piston. bore hone and send back with gaskets if you ask for them (which you should)
if you have enough to spend on the KOR work on the top end, its only $60 to get a head machined. the head will give you a great power increase for being only $60
Tell him you want to run 91 octane and he will set the squish for you to make that possible.
i know you dont want to mix fuel, but its fairly simple and easy to do. and you can feel the difference from injection and pre-mix (you dont need to buy a block off kit, can be done for about $1 just buying a small cap for the carby)
for a better ride, you can find a pair of used front works for about $200 (dont pay more)
and about $50 for a 400ex rear shock and $25(? not sure, dont take my word) for the bushings to run it
-Herp