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Ninja EX500 carbs on an XS650?

Discussion in 'The Garage' started by Highside, Oct 20, 2011.

  1. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    the PO has a 138 fitted which doesn't appear to be rich enough at WOT

    The PO has stated that he has 142 Main jets .

    It would seem a sensible suggestion to me for the PO to try the 142 jets whilst he is waiting for delivery of other main jets .
    If 142 jets turn out to be a slight bit rich they will not cause any harm to his engine .Recommending that someone should start with main jets and WOT testing at a point that is known to be too lean and 'work up' is irresponsible and is not in line with recommended guidelines
     
    Last edited: Nov 2, 2018
  2. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    thats rich coming from the sites main Troll ! Anyone bothering to check any of my past posts will soon see who is the troll that constantly criticises practically every post I make over the past 5 years.

    I'm not going to let you drive this thread into the ground with your petty arguments and vindictive vitriol so I'm going to leave it to you to advise the PO how he should sort his carburation issue. Oh I forgot you don't know anything about carb troubleshooting and setting up do you
     
  3. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    Highboy
    a useful test for testing main jetting on the road is to open the throttles up to full throttle in 4th or 5th gear............ then when the engine seems to plateau or run out of steam... back the throttle off very slightly ........about 1/8th .......... Note what happens .

    Try it a few times until its clear whether the engine seems to hesitate (rich mixture ) or it seems to pick up slightly as the throttle is backed off 1/8th .
    If the engine picks up the mixture is likely too lean and you will need to go up on your main jets .

    if the engine hesitates or shows no response then its likely your main jets are either too rich or they actually may be close to optimum ,(check plugs after long test ride at 3/4 to WOT )in which case you'll need to look elsewhere for the power drop ie exhaust...
     
  4. highboy_coupe

    highboy_coupe XS650 Addict

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    Thanks for the tips guys, going to get some early morning high speed runs in to tomorrow.
     
  5. 5twins

    5twins XS650 Guru Top Contributor

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    Highboy, if you roll off slightly from WOT and the bike pulls better and harder, that's usually a sign your main is too big, not too small like peanut said.
     
    highboy_coupe likes this.
  6. highboy_coupe

    highboy_coupe XS650 Addict

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    Cool, I'm sure with a range of jets I'll get it sorted. Around town it's brilliant!
     
  7. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, you seem very close. You're probably no more than one little tweak or jet size change away.
     
  8. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    You seem to be contradicting yourself 5T . This is an excerpt from your 'carb guide' in which you state

    'under full throttle applications. If the bike pulls clean through this RPM range with no flat spots (lean) or no stumbling or break-up (rich), go up a main jet size. If you do encounter a giant flat spot where the bike just kinda dies, then takes off, that's lean

    to be fair there seems to be varying opinions about this if one surfs the net
    but it really does not matter either way.

    My suggestion of testing the throttle response at WOT by rolling off the throttle slightly and noting the response is a standard test and all that matters is the result .

    If Highboy trys the 142 mains that he has there will be a difference in performance and that difference will tell him which way he needs to go with his main jets . Richer or weaker.

    personally i don't believe that the main jets are the only issue here anyway.
    Everyone seems to be overlooking the fact that the engine was apparently performing fine before the exhaust change !.......;)
    Exhaust tuning is a complex subject and we have no real details about the replacement exhaust other than its bore size. Here is where a dyno session would prove valuable to see where the power curve lies comparing the 2x exhausts
     
    Last edited: Nov 2, 2018
  9. 650Skull

    650Skull Dinosaur Lives Top Contributor

    Peanut statements in red in his 5twins quote.
    index.png

    1 dram to many LOL
     
  10. 5twins

    5twins XS650 Guru Top Contributor

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    Yes, I know he said that, but you can't tell this guy nuthin' ...... He pretty much forgets what he wrote in 20 minutes, lol. And his quote from the carb guide is incomplete and out of context. I'm pretty sure it's part of the midrange to main transition tests, not the main jet test.
     
  11. 650Skull

    650Skull Dinosaur Lives Top Contributor

    yes i see the difference in the references.......Shame he doesn't read things properly himself instead of blaming others for doing the same thing.......

    It feels a bit churlish posting his quotes to counter his claims. ..............................He actually gets people to listen to him through his browbeating of others who post contrary information to his...........makes out hes an injured party when other posts are different, because other opinions/information/facts are not the same as his.............. I removed my input after i bought a set of these carbs due to his argumentative behavior..........he changed a previous post so that information i posted after him was made to look like he had posted it first and then proceeded to berated me...........
     
  12. highboy_coupe

    highboy_coupe XS650 Addict

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    Ok..
    Just to clarify, you can see the exhaust here:
    IMG-20181010-WA0001.jpg
    It's a 1.5" 2 into 2 system, no crossover. There's perforated steel mesh inners in the mufflers but they are straight through, like many aftermarket systems, and an extra drag pipe baffle is then held in each one by a bolt.

    Everything was pretty much perfect before the exhaist, and it ain't too bad now! Just that slight difference in top end. I considered the CVKs perfectly dialled in with 38/138 and the jjj needle. So the exhaust is the only factor here, and it is probably less restrictive than the standard pipes.
    In line with what most people have said, yes it probably wants a bigger main; midrange is still great, idle is good, it never splutters or bogs down on snapping the throttle opens.
    By comparison, snapping the throttle on the BS34s would nearly almost stall it, midrange was lumpy, but top end was fine.

    Cheers for every other news help, I certainly didn't want to start any arguments!
     
  13. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    Main Jet Testing using the 'Roll Off' method as recommended by the Mikuni American Corporation in their carburettors Tuning Guide.

    http://www.mikuni.com/fs-tuning_guide.html
    quote '
    1: Main Jet Size: How to Get it Right
    ROLL-OFF:


    The Roll-Off technique is the quickest and is almost as accurate as the Roll-On method. First, one gets the engine warm on the way to a safe roadway. If there is room, use fourth gear as this allows more time to assess the result.

    Now, get the engine rpm high enough that it is on the cam and in its power band. This may need to be as high as 4000 rpm with some cam choices. Apply full throttle. Let the engine accelerate for a couple of seconds until it has settled in and is pulling hard. Quickly roll the throttle off to about the 7/8ths position. When you do this, the mixture richens slightly for a second or so.

    If the engine gains power as you roll the throttle off, then the main jet is too small
    (ie too lean) and you need to fit a larger one.
    If the engine staggers slightly or has a hard hesitation, then the main jet is too large ( ie too rich) and you need to fit a smaller one.
    [​IMG]
    Copyright (C) 2002, Mikuni American Corporation All Right Reserved.

    5Twins post #907
    Looks like you have your lean and rich mixed up :) but regardless ...what matters is ones personal experience and my experience is that when you roll of the throttle 1/8th at WOT in a high gear if the engine shows signs of picking up then the mixture is too lean and the Main jet needs increasing is size NOT decreasing in size
     
    Last edited: Nov 3, 2018
    Jim likes this.
  14. highboy_coupe

    highboy_coupe XS650 Addict

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    Ok, little update, rolling off full throttle gives a slight burst of power, so that is just confirming the lean hypothesis! Now to try again with the bigger jet...
     
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  15. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    It will be interesting to see the result of using the 142 Mains.'
    What have you got your re-jetting mains turnaround time down to now I wonder ?;)

    I hope you haven't been doing 90mph in todays winds lol :eek:
     
  16. highboy_coupe

    highboy_coupe XS650 Addict

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    Carbs off, jets in and carbs back on takes me 15 minutes!
     
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  17. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    damn thats quick ! :)
     
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  18. Jim

    Jim Beyond the edge, is the unknown. Here be Dragons XS650.com Supporter Top Contributor

    Put allens on the float bowls. Then you can pull bowl and change jets without removing the carbs. Gets you down to 5 min.;)
     
  19. peanut

    peanut XS650 enthusiast & inveterate tinkerer XS650.com Supporter Top Contributor

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    we need to see a video of this Jim so that we can time you :laugh2:
     
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  20. highboy_coupe

    highboy_coupe XS650 Addict

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    Luckily someone got there before me, everything on the carbs is already Allen head; I just don't have the skill work upside down so I'm afraid the carbs have gotta come off!
     
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