Depending on the pipe you will most likely want either a 155 size main jet or a 160 size main jet. However since these things take a bit of playing around/fine tuning, I would suggest you purchase either a Dynojet jet kit or a JD jetting kit, personally I haveheard the most positive feedback regarding the JD kit but it seems like much of a muchness as I ran the Dynojet and it was mint. If you want to make sure you have all the parts for it (some carbs require you to drill out a small plug for proper installation) then that is probably the way you want to go.
Dynojet's page with the SM kit:
http://www.dynojet.com/jetkits/motorcycle/suzuki.aspx
JD jetting:
http://www.jdjetting.com/xcart/produ...3&cat=9&page=1
Assuming they are properly installed, ie you don't mess up the install and run a crazy lean jetting setup you are unlikely to notice any negative impact on the engine. I mean, you're putting more fuel/air into the cylinder hence bigger explosions hence more power so it's the sort of thing, you might only get 45,000kms from your DRZ instead of 50,000kms.
However if you look on sites like advrider, supermotojunkie, thumpertalk there are stories galore of people doing the full big bore, cams, FCR39mm etc and achieving that sort of mileage on the same top end. Hell I even read one thread where a guy claimed to have thrashed his DRZ day in, day out, with all the good stuff on it, having done dirt, trails, racing, and had it blow up on him at 60,000 miles. With that said, you probably shouldn't be bothered by a few intake/exhaust mods. My 2c. Enjoy your bike. They go much, much better with those mods, but I'm told the FCR carb is when things really start to pick up. Things like your front wheel.
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