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HELP sportster stumbles in midrange

Discussion in 'Motorcycle Tech Talk' started by HD4ME145, Jul 25, 2007.

  1. HD4ME145

    HD4ME145 New Member

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    HEy guys,

    Im new to this forum and just wanna say really cool site, very helpful. I have been searching and cant seem to find a duplicate of my problem on the forums so here goes.

    I have a 1996 sportster 883, with 1200 cylinders, wiseco 10.1 pistons,stock 883 heads,2" drag pipes , a k&n airfilter, and a mikuni hsr 42mm carb:cool: . My problem is i have a stumble and my plugs are coming out black so i know its rich. It runs really well if you get on it hard and rifle thru the gears, occasionally breaking up on top till about 4th gear, i am guessing midrange as when i get on it, it cleans out. Then if i am cruising and i find the right rpms(no tach):eek: and the right gear combo i will get the same stutter and if you gas it, cleans out again. I have some experience with carbs just not on harleys, so i get the just of them. I tried holding my throttle at the stutter point and shifting up and it will go away a little, i just dont know if the entire problem is in the carb.

    Is my ignition not strong enough for basic mods?:confused:

    Are the loud pipes just to much for this bike?:confused:

    Is the carb to big?:confused:


    I really am not to sure because overall i like the way the bike performs, i just want to clean it up, any help would be greatly appreciated


    thanks
    mitch
    HD4ME145, Jul 25, 2007
    #1
  3. chucktx

    chucktx Moderator Staff Member

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    welcome to the asylum!!!!!;) ,, the first thing i would do is baffle the dragpipes.....then see if it still stumbles. the only good that a drag pipe gives is noise, and wot responce, other than those two things they hurt preformance more than enhance it. i think once you address the dragpipes you will find that your bike is a screamer........have fun and stay safe!!
    chucktx, Jul 25, 2007
    #2
  4. cowboy

    cowboy Moderator Staff Member

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    mitch, a few queston's here
    1 are your pipes baffeled in some way
    2 what jet's where in the stock carb verse the new carb? you might be able to just reset the mic carb down by truning in the screw
    you should have some type of baffle to get full power out of you engine, don't need to clog it up just enough to give some back pressure, & you can still be loud & proud
    :cool:
    cowboy, Jul 25, 2007
    #3
  5. HD4ME145

    HD4ME145 New Member

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    thanks for the tips, NO baffles in the pipes, bike the work done 2 it when i purchased it off a friend. i basically did most of the motor work with him, then he did the carb rode it a little and i bought the bike off of him. so i know the history of the bike, i was thinking baffles i really know they would help. before i do that i have some other mandatory items i need to do, thats why i was questioning jetting, as that would be a cheap way to just clean it up now until i run into some coin.Also wat about a 1 step hotter plug?
    HD4ME145, Jul 25, 2007
    #4
  6. maxpower_hd

    maxpower_hd Active Member

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    Welcome to the forum. What part of MA are you in? I'm in Billerica and know quite a few people in the construction field as well. I also do side work here and there with some of them.

    Here is a link to the tuning guide for the Mikuni carb. That should help out a bit.
    http://www.mikuni.com/pdf/hsr_tuningmanual_021003.pdf

    I've had three of these carbs now and have found them to be pretty easily tuned. I've never had to rejet either. They have always worked pretty well right out of the box with just a little tuning. I've never had an 883 though so maybe the 883 heads have something to do with it. Either way, the guide walks you through what to do.

    Good luck.
    maxpower_hd, Jul 26, 2007
    #5
  7. whacker

    whacker Active Member

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    I put some AR cones in my 75 sportty and it made a big differance ,kinda a cheap item ...20 bucks...made the bike run alot stronger,I run drags too,but had modified baffles...
    whacker, Jul 27, 2007
    #6
  8. HD4ME145

    HD4ME145 New Member

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    thanks for the tipa again, you guys are awesome. I am out of berkshire county mass right by the vermont border, got some relatives that live in billerica! Seemed to have fixed the problem, took the carb right off cleaned and inspected, wasnt dirty but while it was apart, only thing i changed was i went to split fire plugs and i raised the clip 2 spots on the needle so now it is in the 4th position from the bottom and did a plug reading and they are looking good, no signs of a lean condition and i have about 300 trouble free miles on since then! cleaned the midrange up real nice and runs noticibly smoother throughout the rpms as well!!!
    HD4ME145, Jul 28, 2007
    #7
  9. Tomflhrci98

    Tomflhrci98 Active Member

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    Welcome aboard Mitch.
    I can hear your accent ....... paaak the caaa :D

    I was born in Fitchburg MA and after 6 months my family moved to Billerica. After another 6 months we moved to Rhode Island and I never stepped foot in MA again. My loss. :( I've always wanted to go back.
    Tomflhrci98, Jul 28, 2007
    #8
  10. kenfuzed

    kenfuzed Administrator Staff Member

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    I've seen it many times on unbaffled drag pipes. In some cases you can actually experience fuel-standoff, where reversion pushes the fuel mixture all the way back out the carb creating a vapor cloud in front of the carburetor, then drawing it back in causing a stutter and surge.

    One super cheap way to cure it without having to install baffles is by using a 1/4" bolt on each pipe. You drill a hole through the end of each pipe and pass the bolt through each. Fasten with a nut and some locktite. This creates a split in the path of the exiting exhaust and is often enough to eliminate midrange problems. You would think that a thin bolt would have no effect but you'd be surprised how well it can help on straight drag pipes. Best thing (besides the cheap part) is you won't lose any sound... other than your own hearing :p
    kenfuzed, Jul 29, 2007
    #9
  11. whacker

    whacker Active Member

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    I highly recommmend the AR cones,from my experiance,my acceluration improved,bike run so much stronger,really amazed me for 20 bucks,went from 42 mpg to 47mpg's......
    whacker, Jul 29, 2007
    #10
  12. HD4ME145

    HD4ME145 New Member

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    NO accent here, that bolt trick seems interesting, i mite give that a try, i was looking into the ar cones, but i am not to concerned with gas mileage, mainly just trying to be loud and piss off the new neighbors who seem to be anti motorcycles, they are gonna be in for a ride when they find out that the people on the other side of them ride as well!!!
    HD4ME145, Aug 1, 2007
    #11
  13. whacker

    whacker Active Member

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    If you weren't so far away I would ride around your neighbors house!!!!!!
    whacker, Aug 1, 2007
    #12
  14. voodoochild

    voodoochild New Member

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    I might have to take a ride up there just to piss in somebody's wheaties! I love doing that. Maybe we could have a burnout contest......you got a paved driveway?? :D
    voodoochild, Aug 1, 2007
    #13
  15. HD4ME145

    HD4ME145 New Member

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    yep shes paved, left on a ride tonite bout 14 of us or so and made sure to set off a few car alarms in the process!
    HD4ME145, Aug 1, 2007
    #14
  16. voodoochild

    voodoochild New Member

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    Nice!!
    voodoochild, Aug 1, 2007
    #15
  17. chucktx

    chucktx Moderator Staff Member

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    well. if ya got concrete drive, here is what it can look like after a small burn out.....
    the "spot" in the drive is about 1/4 inch deep.....lol

    Attached Files:

    chucktx, Aug 1, 2007
    #16
  18. hotroadking

    hotroadking Super Moderator Staff Member

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    Hey chuck you tired of making corners, just wanted one of the straight line tires on that thing LOL

    The bolt trick in the mufflers works, you can run it through the existing hole for the baffles.

    BTW put the baffles back in, couple of reasons

    1) Loud pipes are great but if you piss enough people off you end up with noise regulations like in Denver where you can't run any pipe but a stock EPA certified pipe on any motorcycle now. There are a lot more people that don't ride that can vote us into a corner

    2) Baffles improve performance, you probably are killing the low to mid range where you ride 90% of the time. So you're not only hurting your power you're putting yourself in a position to not have the power you will want when it comes time to twist the throttle. Baffles will increase the low to mid range power where you ride and you'll feel the difference.
    hotroadking, Aug 2, 2007
    #17
  19. HDManic

    HDManic New Member

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    bolt

    The bolt trick works and is a cheaper fix.. Geo
    HDManic, Sep 14, 2007
    #18

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