ok, so this is my first post as a new member. I've searched for my answer through previous threads but nothing matched my exact problem.
here's what i have...
91 sportster 883
k&n air filter with the back side of the air box opened to allow more flow
equal length drag pipes with no baffle. < bad idea i know... hind sight>
thunder-slide kit

OK so here's my problem. before i installed the thunder-slide kit i was having an issue only at the top of 5th gear between 3500 and 4000 rpm. at that range the bike would just hit a wall.... it didn't back fire or pop through the carb it would just sputter similar to a miss fire and not go any farther in the rpm range. i always thought this was a jetting issue and since i planned to do the thunder-slide kit , ignored this problem as my plugs never showed signs of running lean.
so... last week i installed the thunder slide kit and this little problem became much worse. at first i had huge mid-range problems that i was able to get rid of by jet and needle adjustments. however, my top end problem still exists and now involves 4th gear as well.
here is exactly what it does... if i slowly increase throtle in 4th or 5th it hits this wall at around 3500 rpm in 4th 3200 rpm in 5th... but... if i hammer it to the point where i drop into the gear above 4000 rpm it'll rap 4th out to 6000 and take 5th to about 5000 at which point I'm hitting wind drag limits...
I've tried everything i can think of and some other things I've read

carb details after 2 weeks of adjusting

thunder-slide kit
dyno-jet 180 main
needle set at the 6th notch from the top
48 slow jet
took the thunder-slide spring out today and put in the stock spring thinking it might help... lost all my new gained throttle response and didn't help my problem so i"m putting the lighter spring back in

I'm beating my head of the wall at this point so please... any help would be much appreciated

 

Bump... Anybody?

 

I never had this problem & can't offer much; but, it doesn't sound like a carb issue to me. Maybe try a leak down test to verify everythings tight & valves are seating. If all's well there start troubleshooting the ignition. Also, if you have adjustable pushrods take a look at them & the lifters.

 

It's an 883. They don't have a lot of high rpm pull in 5th gear.

 

i was afraid this might be the answer. ill check into it and post what i find.

 

its not a lack of pull... its more of a stutter... its like its miss firing but only at the 3500 rpm range

 

it sounds to me more like an ignition problem. is it still the stock ignition ?? If you stay in the throttle when the sputter starts can you drive through it ?? or does it just stop accelerating all together ?? dsv

 

Is the ignition in the nose cone or is it a external module? One the cylinders not firing?

Nose cone ignitions usually fail due to the high heat in that area.

 

im afraid to push it to hard when it starts acting up. if i stay in the throttle in 4th it'll climb some what but in 5th it just stops dead. i found that backing out of the throttle helps and some times i can slowly work it past this bad spot if i baby it. so i thought this might be a fuel starvation issue. a few days ago i took out the petcock and cleaned the screen and inside the petcock itself. i rerouted my fuel line to insure the best flow i even took the bowl off and watched the fuel flow into the carb which seemed ok... i also seafoamed the gas and let it sit for a few days. all which made no difference. thinking i might have a weak coil i turnded the plug gap from .040 to .030 again with no difference... im out of ideas
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its under the triangle cover behind my battery