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XJ650 Won't go over 75 MPH

Discussion in 'XJ Technical Chat' started by bigjoe88, Sep 21, 2019.

  1. bigjoe88

    bigjoe88 New Member

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    I have an 82 xj650 maxim the speedo goes to 85 I was wondering if there was a governor or so.ething I could remove to push another 20 mph out of it
     
  2. Kickaha

    Kickaha Active Member Premium Member

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    Just because the speedo stops at 85 doesn't mean the bike will
     
  3. XJ550H

    XJ550H Well-Known Member Premium Member

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    there is a thread on conversion to 150mph speedo
    Bigfitz's 550r: 150mph speedo retrofit

    or just add 12 to 15mph to the tach reading 6k rpm=72 to 75 mph it looks to me like the spread of mph increases as the rpm gets higher 10krpm is about 125 mph
     
  4. bigjoe88

    bigjoe88 New Member

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    the bike seems to top out at 75mph theres gotta be a way to push it closer to 100mph
     
  5. XJ550H

    XJ550H Well-Known Member Premium Member

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    sounds like your bike has some issues you should be able to go to red line.
    tell us about your bike how it is set up and what work you have done to it.

    5k to 7k rpm is where the fun starts you should be able to push up to 9050 rpm.
    the XJ can and does run at higher rpm. you should be able to red line in all gears.
     
  6. XJ550H

    XJ550H Well-Known Member Premium Member

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    How many miles on bike?
    shaft drive bike have you changed the lube in the rear end or checked it?
     
  7. XJ550H

    XJ550H Well-Known Member Premium Member

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    you are in the Hang out lounge and should start a thread in the tech forums or have a moderator move this post to the Tech forums. More people will see it there .

    your motorcycle is a collection of systems and all work together. you need to evaluate them all.
    The Information Overload Hour

    Ignition system needs to be ohmed out to give you a good idea on its being in spec. it could be as simple as a bad sparkplug cap, sparkplug.
    specs for ignition system and charging system found in this link
    The Ultimate Relay, Switch, Sensor, and Diodes Guide
    do all your header pipes get hot?
    fuel system starts at gas cap it has a vent . ends at carbs includes air cleaner.
    clogged jets, old air filter or untuned carbs can be the issue.
    IN THE CHURCH OF CLEAN
    Motor check valve clearances is the first step in improving bike performance. shims out of spec can cause low compresion and poor operation.
    Bigfitz's AIRHEAD VALVE ADJUSTMENT with Pics - parts I & II
    after valves are checked then you can tune carbs do not even bother to tune if valves are not set to spec..

    proper lube of drive shaft is important.
    check wheel bearings if those are dry it will slow the bike down.
    rear brakes pull the rear tire your shoes could be delaminating and if you want to drive fast you need solid rear shoes or you could come to an unexpected stop that will not be nice.
    SAFETY ALERT Drum rear brake bike owners please take a look
    safe sound bike is key to surviving the roadways.
     
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  8. bigjoe88

    bigjoe88 New Member

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    I got it with 940 miles on it checked final drive and changed the oil in it bike is completely stock
     
  9. bigjoe88

    bigjoe88 New Member

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    bike is completely stock I changed all fluid did tune up bike had 943 miles on it when u got it
     
  10. k-moe

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

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    Low mileage isn't necessaraly a good thing. That means she sat for a looooong time. Given that she isn't getting up past 75 the first thing I'd look at are the carbs.
    Given the age you're likely looking at a full teardown, thorough cleaning (in carb dip), and replacing the o-rings and throttle shaft seals.
    In proper running order she should pull hard right up to redline (and beyond), reaching ~120 MPH.

    IN THE CHURCH OF CLEAN
    Why you should replace butterfly (throttle shaft) seals.
    Replacing your Hitachi throttle shaft seals
    Setting the fuel levels

    That's not the only possible cause for your troubles, and since she's been sitting so much it's really best to go through everything (particuarly the brake systems), so you don't end up having a trip in an ambulance.

    XJ550H posted the link to the Information Overload Hour. Read it, then do it.
     
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  11. bigjoe88

    bigjoe88 New Member

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    brake system and tires were replaced first thing carbs were opened but not thoroughly cleaned
     
  12. bigjoe88

    bigjoe88 New Member

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    I just bought an 82 xj650 maxim it had 943 miles on it when I bought it first thing I did was change all the fluids tires and brakes.no modifications have been made to this bike I did have a problem with a hung up float pulled the carbs free up the float changed the oil again problem is I cant push this bike passed 75 mph what should I be looking at and suggestions would be greatly appreciated thank you
     
  13. k-moe

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

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  14. Jetfixer

    Jetfixer Well-Known Member

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    ^^^+2 ding ding you need to get religious on carbs, ( church of clean) a full tear down and soak carbs is the ONLY way to clean out the small passages of the carb. Spray cleaner will NOT cut it. You will need to replace ALL the rubber seals, butterfly ,fuel rail, mixture screws O rings . The other item check the valve clearance even if mileage is low , have you checked compression ( rings ) remove all 4 plugs, with fully charged battery check compression both dry and wet. Have you put in new and properly gapped plugs? All of these items can effect running. For parts upper rt corner xj4ever has all these parts.
     
  15. Ryengoth

    Ryengoth Active Member

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    Even a soak isn't always good enough. Pluck a wire from a cheap wire brush. Most of them work well to clean out all of the small jets on the carbs.
     
  16. Minimutly

    Minimutly Well-Known Member

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    If you have a problem with the bike not making power (which is why it can't go over 75), the issue is NOT idle or primary circuits (the small jets), nor is it throttle spindle seals. If its carb related the only culprits could be main jets and or emulsion tubes. Pull the carbs, drain the fuel, tip them upside down and remove the float bowls. You then need to remove the tops, diaphragms and slides. Tip them over, Unscrew the main jets, and with a suitable drift, careful not to damage the bottom seats, tap the emulsion tubes into the carb throats.
    Should you find they are clean, you should be looking then at your air filter (remove to test), then you should wonder about the inside of your exhausts - at the age of yours they may be totally blocked.
    By all means do the church of clean thing, you surely will need to, but its only benefit to your current problem is the main jets area.
     
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  17. Jetfixer

    Jetfixer Well-Known Member

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    ^^+1 that is spot on , exhaust baffles could be blocked or collector box. Agree emulsion tube is probably gummed up.
     
  18. Simmy

    Simmy Well-Known Member

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    Does it rev freely in neutral?
    Can you run to redline in lower gears?
    Are the brakes dragging?
     

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