1. Some members were not receiving emails sent from XJbikes.com. For example: "Forgot your password?" function to reset your password would not send email to some members. I believe this has been resolved now. Please use "Contact Us" form (see page footer link) if you still have email issues. SnoSheriff

    Hello Guest. You have limited privileges and you can't "SEARCH" the forums. Please "Log In" or "Sign Up" for additional functionality. Click HERE to proceed.

High RPM Stumble

Discussion in 'XJ Technical Chat' started by patmac6075, Apr 29, 2016.

  1. patmac6075

    patmac6075 Active Member

    Messages:
    415
    Likes Received:
    50
    Trophy Points:
    28
    Location:
    MKE
    So I'm just about finished with this Seca 550 (Complete carb rebuild)
    Bike starts easy enough with choke (still 50 degrees here)...once warmed up it'll idle around 1200 RPM. Throttle doesn't hang...carbs have had a running sync.....I no longer have a colortune, so I've adjusted mixture by ear (none really took more than 1/3 turn out off of the bench set 2 1/2 turns out, most were less)....checked the plugs and they seem to be getting a slight brownish color...Bike pulls nicely up to about 7000RPM and begins to bog, not a lot....you can just kind of feel it....it'll pull to redline, just not cleanly (using my 750 as the bench mark).

    Suggestion?

    Valves done and oil, oil filter and air filter done
     
    patmac6075, Apr 29, 2016
    #1
  2. mrdawson

    mrdawson Active Member

    Messages:
    180
    Likes Received:
    38
    Trophy Points:
    28
    Location:
    Wisconsin
    stock airbox, filter etc?
     
    mrdawson, Apr 29, 2016
    #2
  3. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,647
    Likes Received:
    6,756
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    Did you pull the emulsion tubes (needle jet) out during cleaning?
    I'll assume that you carefully inspected the diaphrams and polished the slides.
     
    k-moe, Apr 29, 2016
    #3
  4. patmac6075

    patmac6075 Active Member

    Messages:
    415
    Likes Received:
    50
    Trophy Points:
    28
    Location:
    MKE
    Stockairbox...
    Carbswerecompletelydisassemble,cleaned,andinspected.
     
    patmac6075, Apr 29, 2016
    #4
  5. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,647
    Likes Received:
    6,756
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    Hmm..... maybe a vacuum leak.
    Are the sparkplugs new? Might one be misfiring under exreme load?
     
    k-moe, Apr 29, 2016
    #5
  6. k-moe

    k-moe Pie, Bacon, Bourbon. Moderator Premium Member

    Messages:
    19,647
    Likes Received:
    6,756
    Trophy Points:
    113
    Location:
    The City of Seven Hills
    Or..... I wonder if it might not be the early signs of clutch slippage.
     
    k-moe, Apr 29, 2016
    #6
  7. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,861
    Trophy Points:
    113
    Location:
    Great North Woods
    is this problem in all gears?
     
    XJ550H, May 1, 2016
    #7
  8. patmac6075

    patmac6075 Active Member

    Messages:
    415
    Likes Received:
    50
    Trophy Points:
    28
    Location:
    MKE
    Yes
     
    patmac6075, May 2, 2016
    #8
  9. patmac6075

    patmac6075 Active Member

    Messages:
    415
    Likes Received:
    50
    Trophy Points:
    28
    Location:
    MKE
    Could it be fuel starvation? Right now I have an extra long (new) fuel hose, waiting for a 90 degree filter to come in before I trim hose and maybe that long hose has some air bubbles (I'm just spit-balling here)?
    I don't think it's the clutch slipping as the engine bogs more than slips/races.
    It could be a vac leak at the sync nipples as those caps were rock hard.
    Anything else I should look for?
    Oh, and yes....plugs are new and gapped.
     
    patmac6075, May 2, 2016
    #9
  10. cgutz

    cgutz Well-Known Member

    Messages:
    1,203
    Likes Received:
    719
    Trophy Points:
    113
    Location:
    SE South Dakota
    Are valve clearances in spec?
     
    cgutz, May 2, 2016
    #10
  11. XJ550H

    XJ550H Well-Known Member Premium Member

    Messages:
    13,199
    Likes Received:
    3,861
    Trophy Points:
    113
    Location:
    Great North Woods
    you can get the caps at the auto parts store 5mm
    I use translucent fuel line to see air bubbles. if the hose goes high you can get a air blockage in the hose. putting petcock on prime will draw air bubbles out unless they are trapped by hose height
    I used 90 degree vac/fuel fittings first one at the fuel tee to direct my hose second one to make the corner to go to filter and petcock.
    the hose routing is critical in a gravity feed system
     
    XJ550H, May 2, 2016
    #11

Share This Page