The K&N R-1260 is a direct fit to the carb opening, but the length and diameter of the filter will not fit without modification.

To mount mine, I had to cut away the top of the factory air box AND remove the top of the battery box to provide clearance.

Was it worth it?   The butt dyno says yes.  Better throttle response (especially when accelerating to pass on the express way) and much better sound.  

A rejet will be required to compensate.  Also, you can completely remove the white spacer once the filter is installed.

I have thought about just cutting a hole in the top of it (its plastic) to provide clearance for the filter and still look pretty. Haven't done that yet.  I'm running the emgo filter as well.  I should mount the K&N but have been a bit lazy of late.....

Buy one of the performance cone air filters for sell on this site.
They are better, don't require oiling, fit straight on and are cheaper than a K&N.

here is the info provided by "Lancer".

I have contracted with a manufacturing company to build a custom designed Performance Air Filter for the Suzuki Savage & S40 . This filter is of a similar design but superior to a K&N filter. This new filter remove dirt particles better than a K&N, will move more air than a K&N, does not require oiling, is washable/reusable, and costs less than a K&N. This filter is a cone shaped design of the following deminisions: 4" long 3" OD on the big end 2" OD on the cap The price on this superior air filter is just $39.95. Compare to a similar K&N filter that retails for $55-65. Why pay more and get less ? ?

This product is brought to you by Alliance Member "LANCER"

There was a problem with them breaking so Lancer took them off and is going to b!tch out the manufacturer.

For Mikuni VM roundslide performance carbs

SN-2570  
flange:   2.438 in (62 mm),  
big end OD: 3.5 in (89 mm),
small end OD:  2 in (51 mm),
Length:  5 in (127 mm),
end cap: Rubber  

SN-2530
2.438 in (62 mm)
3.75 in (95 mm)
3 in (76 mm)
4 in (102 mm)
Rubber


For stock carbs


RC-1250
2.25 in (57 mm)
3.5 in (89 mm)
2 in (51 mm)
4 in (102 mm)
Metal  

RC-1252
2.25 in (57 mm)
3.5 in (89 mm)
2 in (51 mm)
4 in (102 mm)
Metal

RC-1253
2.25 in (57 mm)
3.5 in (89 mm)
2 in (51 mm)
4 in (102 mm)
Metal


R-1260
2.25 in (57 mm)
3.5 in (89 mm)
2 in (51 mm)
4 in (102 mm)
Rubber