I'm a newbie and would like to say hello to all. I'm impressed with what I've seen in this forum. I last owned a bike in 1982(modified XT500), and purchased a brand new 2011 S40($3,999) on 8-21-12. I was surprised at how poorly it seemed to run when I first started it up at the dealership. Also surprising was the lack of spacing between 4th and 5th gear. I've already removed the brass plug and opened up the mixture screw. I will be making other carb changes(pilot, main, spacer), a better muffler, and Amsoil. It sure is fun to be riding again after a 30-year hiatus. I do have questions. Does the head really need to be retorqued ? Will a Clymer manual 1986-2007 work for my 2011 for everything ?  Is it worth getting a Suzuki manual, as well ?  

If you brought it new you could be risking your factory warranty by making unauthorised modifications to the fuel/emission system. If you were able to remove the brass plug without damaging it, you should consider putting it back. If you had to damage it to get it out, see if you can dummy up an authentic looking one. I would also leave rejetting alone until you are out of warranty. They are basically a cheap bike and a sixth gear would only up the cost. $3999 US sounds very reasonable compared to what you pay in my country.

I put a screw in it and pulled it out with pliers(it's toast). The mixture screw was about 1.65 turns out CC. I gave it another 1/2 turn out - idle went up, twisting the throttle back resulted in a cleaner rev, and it added a little overall power(turning more out CC didn"t seem to help). It also reduced backfiring to a minimum(not as lean- still needs a little more). The only negative appears to be mileage(lost what seems to be 6-7 mpg). I'm not sure how your bike arrived to you(new from the factory or otherwise), but here in Kennewick,WA, this bike needed opening up to just run closer to normal.  

ZAR wrote on 09/25/12 at 16:41:01:

+1

  I hope I didn"t appear rude-not my intent   things that I mentioned(screw-pull out brass plug-adjust mixture screw   main/pilot/spacer  muffler   oil with enough ZDDP   I got from this site   I worked at an engine shop from 1987-92   haven't turned many wrenches in 2 decades   I'm ready again   some of the posts I've read are great   there seems to be many ingenious  minds at work   Verslagen 1 - Oldfeller - LANCER - Sluggo(fellow Eastern- Washingtonian) to name a few     I also want to get the Verslagen modified tensioner unit   I have 1100 miles on the bike and am looking forward to thousands more  

Awesome for you, dude!  Great group of folks here, and great little bikes!

I only suggested putting the plug back in case you have to make a warranty claim. If they see something that looks brass they probably won't argue and you idle mod is safe.

Mine has 20,000 on it,, never did it.. was gonna, at 15,000 when I did the cam,, but got all wound up messin w/ the cam & chain & all that & uhh,, ahh fergot,, dooohhh,, Im glad, didnt hafta wrangle w/ that danged plug,,