You can temporarily make it less noticeable with another 1/4 to half turn out, but down low may be a bit rich. If you just lightly blip the throttle and the revs when coming back down to idle go below idle then recover you're too rich on the pilots. If you blip the throttle and the idle hangs up higher than idle and floats back down you are too lean. Make sure your %100 warmed up before adjusting, at least a 20 min ride in winter.
If you would like you can get some shims at radio shack and put one on the needle this will lift it making it richer in that dead spot probably eliminating it. I'm assuming you have an American bike with non-adjustable needles.
Radio shack shims part #64-3022A
I would only put one shim under c-clip of the needle or the plastic "doughnut" to raise it a bit, If it's that horrid stock exhaust and mid-pipe. I'm not sure where you are but it is winter and colder temps require richer jetting. These bikes are super lean out of the factory to get by emissions. However on the bright side they are almost stupidly easy to tune. If you like take one of the outside carb float bowls off and read off the mainjet and pilot jet size for us so we know if it's stock or not. Stock exhaust on there?
When I first got my bike and before I piped and rejetted it I set all the screws(mine were all over the place too, out of the factory) to the stock 3 turns out on my Gen2 and it was smoother, but even with the stock exhaust it was kind of weak. Turning the screws out a 1/4 turn extra and adding 1 radio shack shim given to me by another forum member, really helped especially when cold, it improved warm up as well as cruise smoothness and throttle response. Try another 1/4 turn and see if it gets any smoother. 3500 is just right at the transition period from the pilots to more of the needle and mains. So either shimming which will give that lean area more fuel, or another 1/4 turn or so will do the same and smooth the cruise out. Your choice. Personally I would do both, add 1 shim and another 1/4 turn as these bikes are super lean, it may not totally fix it(really need a rejet and aftermarket mid-pipe and slip on) but it will drive %100 better.
If you're going to get an aftermarket slip on, make sure it comes with a mid-pipe as well. The stock mid-pipe is super restricted and just getting a slip on is not going to do it. It's literally a waste of jets unless the mid-pipe which is at least a good %60-70% of the restriction is replaced. They are cheap I got my Muzzy slip on and mid-pipe on Ebay for $150 shipped. It came with a centre stand stop and everything. But if you buy one that doesn't have a centre stand stop you can fabricate one out of heavy sheet metal for a few bucks.
Here is a place to get a slip on and mid-pipe cheap with free shipping in the States, however they do not offer a centre stand stop so you will have to buy a few dollars worth of sheet metal and fabricate a centre stand stop. I can describe mine which fits over the centre stand existing bolt, it's doesn't need to be super strong it's basically a piece of metal the centre stand can rest on. Or you can pay like $30 from Holeshot and get a fancy one. Bottom line if it doesn't have a mid-pipe DONT BOTHER WITH IT, get something else. People here have been stuck with super expensive end-cans that do almost nothing because they didn't check to see if the setup came with a mid-pipe. One guy we were helping is going to buy a whole Dan Moto system just to steal the mid-pipe which is a pricey fix, Considering his two brothers slip on is $300 and does almost nothing without a mid-pipe.
Cheap slip ons with mid-pipe systems:
http://www.dan-moto.com/DM_US/gsf-bandit-600-1200-n-s-wholesale-18_20_58.htmlJust a word about the Dan moto exhausts they will sound awsome but may be a little loud for you, I've seen videos and the quietest one is the triangular because you can stuff more packing material in there. So if you want a stealthy but healthy sound go for that. If you want a full bore jihad-mobile go for the carbon fibre or the GP or whatever. Or go with a pricier setup but I'm just giving you the cheapest option. Also you can buy a jet kit for $150 or if you know what your doing we can give you the jet sizes and you can go and pay $10 for jets and use the Radio Shack shims, it's up to you. It invovles modding the airbox lid for better airflow and adjusting the needles/mixture screws it's pretty easy. I recommend you try the $10 option and let us help you tune it for free. You sound very competant and these bikes are so easy to tune is almost silly.
So for $130 For a dan moto special and $10 in jets, you get 10-15 horsepower extra + non wonky stock lean jetting. It's the best $150 you'll spend.
But maybe wait until all the little bugs are worked out first, you're making alot of good progress, best not to change too many things at once until all is good. Although on the other hand replacing the jets will guarantee that they aren't gummed up. Maybe get all the materials first, ie exhaust, jets, Radio shack shims etc. and fix the clutch cylinder. Once it has all that extra power you may want to buy one Barnett clutch spring and pop it in there to beef up the clutch.
