Can't tell you for sure since every bikes going to be different, but I would go up one size on the pilot and main jet, and then adjust accordingly.
http://suzukisavage.com/cgi-bin/YaBB.pl?board=tech;action=display;num=1157720585
You should be able to get the jets from any local bike shop.
As for running no muffler, I wouldn't recommend it. Without any back pressure your going to burn up the valves and its going to be pain in ass to get it tuned proper

+1 to what the others are saying...

The lesson here, is that thumpers are make great torque over a wide power powerband... but not a high maximum HP...
Open pipes will maximize HP,.. but only by narrowing the powerband...

Multi-cylinder engines tend to make great HP, but over a narrow powerband.  
This means they are faster,.. but they have to rev like crazy, and run at high RPM's to get that power.
The thumper,.. gets power over a wide RPM range.
It will pull strongly from idle, all the way up to redline.

Using an open pipe,.. kills that advantage...
It will work well in a multi-cylinder drag racer...
At a drag race, they will rev up to 7k RPM to launch,..(into the narrow powerband) and run fast,... but at idle, or low RPM's they have nothing...

Problem is.... a thumper reaches max RPM at 6500...  the big piston and valves can't move that fast... so, they just don't make good rev'ers...
If you kill the torqueband in a thumper, you kill the advantage of it's design.
So,.. open pipes don't work well in big thumpers...
Thumpers don't make good drag racers.. but they are great in the twisty's...

It may sound sad,.. that a 650 thumper can't beat 650 in-line four... but, it's a different animal,..
While they are revving, and fanning the clutch madly to get power... we are just cranking out our throttle, making it look easy ...

It's like a turtle and hare thing...
... but I think of it more as a rhino a and hare... ...

If you open your pipe too much,.. the torqueband will become narrow, but you will never gain enough HP to make it worthwhile in a big single...

Yes,.. it does...
There's no free ride...
You can afford to narrow, and move the powerband up to some extent... ...but, you don't want to move it out of the range of the capabilities of the engine...
A big piston can only move so fast... and the big valves will start to float above a certain Rpm...

A Harley muffler is a good balance on this bike,.. if you like torque...
Going to a more open muffler might gain another HP or two, but you will narrow the availability of those ponies to an increasingly smaller area of the rpm range...
Eventually,.. your engine feels feeble, unless you are wicking to full throttle all time...
.. and because our engine will only rev up to 6 or 7k rpm's.. you can push the max HP into an area not available to us, without lightening the moving parts in the engine...
Might as well buy a multi-cylinder bike... (smaller pistons and and valves can move faster)... but, then you loose the torque that our big boy has.

You basically trade one for the other at any given engine size,... and slowly climb the scale, adding more cubic inches and cylinders to gain more power... until it just gets silly...

A 650 thumper does a good job at legal speeds, and has impressive zippy-doo-da... at the light and in the twisties...
More than that,.. is for the track, or for collecting traffic tickets...
JMHO...

Note.. there is a certain amount of muffler restriction that is mandated by noise regulations and not performance.  For a big piston,.. our stock mufflers do have a tiny blow hole... I was discussing theory in the above rant, and ignoring the gov't regs...
I bet we're strangling our engine a bit in the stock configuration...
In which case,.. a Harley muff might be giving some gain in both departments, or at least more overall potential... ...

Kutter, my bro lives in Springfield, MO. He runs stock and when we tried to richen up his air mix screw he started backfiring like crazy. His air/mix screw was almost all the way in so I know he's running lean.

He has to run with the choke on (richens it) for the first 15 minutes or so and then after the engine warms up he's good to go.

Personally, I think he could go up a jet size on the pilot and he'd be perfect but he doesn't wanna try and it's his bike so there ya go...

Serowbot, thanks for clearing that up for me.  What you said made a lot of sense, and gives me a good idea of how engine size relates to hp and torque.

Serowbot wrote on 03/07/12 at 08:56:11:


Here's what the stock jets looked like when I took them out of my bike (2005 S40) Main was a 145, Pilot was a 52.5

Hmmm,, I wonder if it's Raaske or homemade.