The mod you have done is all good but it still doesn't change the min bore dimension as this cannot be bigger than the slide and the slide is only just bigger than the bore so does this really work at the end of the day or do you just think it does.
I would spend time on the exh port instead do not widen the port as it is to wide as it is the transfer port as also out a bit but these are not so bad do the exh mod and the bike will rev far better.
Have any of you ever looked at the port timing of one of these, there way out on the exh port. The port timing on the exh was starting to open at around 100deg ATDC where it should be between 87 - 90 (i'm not going to tell you what the best port opening time is, thats for you to find out yourself but start higher and work your way down) Remember if you grind it to high you cannot put it back on and you could have a bike that is to peaky and hard to ride and also to flat on the bottom end but if you grind it so somewhere between 90 and 92 you willo be fine.
It also has a Q port which is a slot extending from the roof of the exh port up by around 10mm to allow the exh gasses to escape earlier and reduce the noise (remember this is a chain saw engine) this port should be blocked off.(JBweld)
Transfer ports where ok as they where at 118 deg ATDC you could change this to 117 if you like the roof angle was fine as well
I then ground in a boost port, to come in 2 deg after the transfer ports (boost port opp exh port) at 60 a deg angle going up to the plug.(you dont have to do this if you dont want to)
I then ground the crank and crank cases, inlet manifold, reed cage, reed stops, carb was ok as it could not be bored anymore. The main jet was changed to suit mods.
When doing the exh mods i found that there was a large lip in the exhaust it was around 2mm all the way round ( it's where the front flange joins the tube)Therefore you could grind this out and increase the exhaust flow? Think about it instead of it being 20mm you can increase it to 24mm it doesn't sound alot but do the calc's
3.142 x 10^2 = 314.15mm^2
3.142 x 12^2 = 452.39mm^2
= 138.24mm^2 bigger in area
= 44% bigger in area
sounds a lot more now doesn't it
worth the check ?
Before and after pics
http://www.glowfoto.com/images/2004/...924417525T.jpghttp://www.glowfoto.com/images/2004/...926564389T.jpg
And when you change the clutch springs for the stiffer ones you want to bend these as well to get the most out of this mod heat the end up and rebend it so it ends up 3mm lower in overall length.
...finally, some pictures to go along with the words. alot of people will find this helpful....make it a sticky..hahahaha. so you didn't drill through the passage to make it bigger throughout? did you do anything to the other side? i was going to use a 9/16" drill bit and drill through the carb to enlarge the intake then use the cone grinder to do what you did to enlarge the inlet. if this is all that's needed for improvements...then i'll just skip the drilling with the 9/16" bit and just do what you did. nice job again!
thanks eater..that was very informative and helpful! i was just going to ask how far in you went...and you answered it. i think i'm going to port the back just a bit also and widen the black plastic port to match the back...should give it more of a venturi action. the problem with the drill press is space, even the mini one...i'm a student living in a small studio and really have no place to put it if i get one...the bike is already taking up space in front of the tv!hahahaha. this should be place in the how-to section sooner or later and not let get lost in the back pages in here...it's good info! once again, great 
