( I put in the whole story of how I came to this perfect setup, so that it can help others figure out what works best for them. I will answer any questions I can)
I just got done putting the final touches to my '06, and I thought I would let everybody know how it went since there seems to be a lot of questions and doubts about what works and what doesn't, when modifying the stock exhaust and air box.
After searching every forum I could find, I began with drilling out the restricter in the neck of the pipe to 5/8". it made a difference, but it had a hesitation if I went from idle to full throttle instantly. I figured that it was starving for air. So I took the snorkel out of the air box,and this made a big difference. I weight 190lb and was able to slowly blip the throttle and wheelie with out having to lean back,and it flat out ran! I was blowing away my buddies atc200m that we've clocked doing over 50mph!
but I still had a little hesitation if I got on it to hard. So I scribed the outline of the hole in the frame onto the air-box, removed it, and cut it out. But after a quick test ride I was ! It had more power but the hesitation when snapping the throttle was worse and I lost a lot of my top end, I clocked it at 40mph !
So I ordered a 85 main, a 40 pilot, and an adjustable needle for a grand total of $48.91, and I waited for them to arrive.
When it came in I installed them, setting the needle on the 2nd from the top because it was the closest to the same length as the stock. after warming it up and adjusting the richness, I found that the top end was back, but half throttle was extremely rough and I still had the hesitation when I snapped the throttle (and I had to run with the choke pulled). so I put it on the 4th groove because a couple of TT'ers had recommended it in other posts, didn't help. so I tried the 3rd,and then the 1st and still it didn't smooth out the middle.
So after searching the forums again and finding nothing, I took some thinking time and I decided to try one more thing. I didn't think it would work but I put the clip on the 5th groove It worked! No more coughing and sputtering, nothing but POWER from bottom to top!
Except for the ever plaguing hesitation!
Which left me with my last mod, the one that I had been thinking about since I cut the air-box hole larger, because it seemed to be getting enough air, but the engine didn't seem to be breathing as well as it should. I decided to take the exhaust off 1 more time! I ground the restricter all the way out and polished the opening smooth with the inside of the pipe and put it all back together.
I just got through taking a quick ride ( because it's 35 degrees outside) and this fixed everything! I now have an instant, smooth throttle response from bottom to top, all kinds of power over the stock setup, and all for under $50
I did not cut out the baffle in the exhaust canister, or remove the spark arrestor. This is what keeps the back-pressure up and help keep the low end power. Plus it is almost as quiet as it was stock, but with more power. in my opinion, with the exhaust mods I've made, there is very little difference between my pipe and aftermarket pipes, so why not save some money!
To summarize, here's my spec's:
Riding elevation 400-1200ft
Air-box cut out to match the frame
Exhaust restricter drilled out and polished
The spark arrestor was kept in place, this makes the bike quiet
Main Jet 85
Pilot Jet 40
Adjustable needle clip on 5th groove
Fuel Jet 1 3/4 turns out
I hope this helps, keep it wide open and don't let off till you see the whites of their eyes!!