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Ninja EX500 carbs on an XS650?

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

  1. highboy_coupe

    highboy_coupe XS650 Addict

    Ok with a few test runs under my belt I can summize that adding the long intakes and restricting the intakes slightly to promote constant pressure does have a positive impact, however, it is mostly felt in the midrange.
    There is a noticable smoothing of throttle transition from low to mid, and a strong (almost frantic) pull through the midrange.
    I got it up to 94mph, but I ran out of road, it was still pulling well.

    I then added 140 main jets and tried again, 96 mph on same road, so no noticable differences with a bigger main.

    I think if I went up to 32 teeth on the back I would have smashed my goal! video to follow....
    grizld1 likes this.
  2. DaveO

    DaveO XS650 Addict

    I have pods and a Motad two into one exhaust and I've done this mod with 38, 138 and JJJ needles. (I thought I'd report back here to encourage anyone contemplating this. If I can do it anyone can.) It runs fine but I've only got a few test miles on the bike as its been laid up for years.

    One problem I have is that when I start up with the enricheners (choke) on it very quickly revs high and needs a bit of finessing to bring the revs down without killing the engine. It seems a little sensitive and pernickety. Also, whilst the enrichener is on there is the occasional chuff or misfire.

    Once the bike bike is off the enrichener everything is absolutely fine and the bike runs sweet as a nut. I'm enjoying riding, so before I pull it all apart again, I but I wondered if anyone else has had this issue or if the answer might be "they all do that"?

    The brass "nail head" on the "plunger / starter" is worn so I wondered the internals are too and if the answer is simply to replace them both.

    kawasaki 16016-1061 random photo from eBay.

    gggGary likes this.
  3. gggGary

    gggGary I'm listening, change my mind XS650.com Supporter Top Contributor

    The rubber on the bottom is the seal. Usually fine but.... worth checking.
    bikefreakjon likes this.
  4. bikefreakjon

    bikefreakjon XS650 Addict

    Yes, sync???

    Also if your mixture isn't dialled in good when hot your idle will be turned up too high to compensate.

    Really dial in that idle mix.

    I ended around 2.25 turns out on one and 2.75 on the other. That was with 38 pilots, uni pods.

    Remember each engine (each cylinder really) is unique!

    People who think they can set the idle mix to a specific number they found on the forum are confused. It has to be done for your engine.
    timbeck, DaveO, gggGary and 1 other person like this.
  5. DaveO

    DaveO XS650 Addict

    @bikefreakjon , that sounds exactly right. I am ashamed to say, I did have to turn up the idle quite a bit and I haven't touched the mixture screws. I was just that keen to ride it.
  6. DaveO

    DaveO XS650 Addict

    @bikefreakjon you are the "carb whisperer". You were exactly right. Thank you so much.

    I lost count of where they were to start but I'm pretty sure I had to turn one in more than the other. I backed them each out 2.5 turns. Started on the first kick with only a small amount of choke. No fiddling. Came off choke by the time I had my helmet on. Ticked over smoothly and moved off down the road. By the time I'd gone a half a mile it was fully warmed up and I had to pull over and back off the tickover screw as it was racing. But even this was completely stable, just far too high. I thought the bike was "OK" before, but it was much better. After a quick fiddle at the side of the road the tickover is probably too low now but its rock solid in comparison to what it was before. I'm years off a bike so I don't know what to expect but I can tell when things are better.

    I'll go through this properly at the weekend. I'm not happy with the choke mechanism I knocked up. It sticks out too far and I have some cap head screws for the carb tops. I've got a stumpy screwdriver which will be perfect for this and I don't use it for anything else so I'm going to pull the screws and grind the screwdriver to be a good fit. Looks like I'm going to be hitting the tech section. What I know about tuning carbs can fit on the back of a postage stamp.


    bikefreakjon and gggGary like this.
  7. I've got mine running quite nicely now. I did have issues which I put down to dirt in the carbs. They looked clean so I'd never stripped them down apart from swapping out jets and setting the float heights. So anyway I got some Seafoam additive that the Yanks go crazy about and gave her a good dose and filled her up with super unleaded. I did have a problem when cold starting. It was like the choke aka enrichener wasn't working right and it was erratic on idle. But now it fires up first kick from cold and I've had to lower the tick over. I can trash it then pull up at a junction and she just idles without fear of stalling. It's a 78 on 38s 138s JJJs Pods and straight thru pipes with VW Beetle muffler tips. Mixture screws 3.5 turns out. As being said above. You can only use forum information as a starting point. I had to drop down from 140s to 138s
  8. DirtyErnie

    DirtyErnie Renaissance Hick

    Mine's been a wild adventure, and I have a lot of needles that could be sold. Settling in in an HKF needle...
    Got close with a set of stock pipes, and then cracked a header. Back on the 2-1 setup, and starting over.
    Think I'm going to make my own exhaust and go EFI.
    gggGary likes this.
  9. ippytattoo

    ippytattoo Just another grumpy old hack.

    Back working on tuning these cvk34's after a change of 4500' in elevation and a 5+ year hiatus. So far the definite changes are that I had to lean the pilot circuit a jet size (from 38's to 35's). I suspect needle and main will probably be rich also. I have 135/138 mains and jjj/jjk needles in case a change is needed

    Last tune for sea level was 38 pilots, jjh needle (clip in 4th slot), 140 mains mix screw 2 turns out. At 4500' it was very rich at idle on sea level tune.

    Current list, 35 pilots, jjh needle clip in middle slot, 140 mains, mix screws at 1.25 turns out

    Anyone else out there running these at an elevation above 4000'? What jets and needles are you running?
    Last edited: Oct 5, 2020
    gggGary likes this.
  10. Bjorn

    Bjorn XS650 Addict

    This is an awesome thread guys! I red it front to back and am surprised that its mainly positive reactions on the keihin carbs.

    Im running a pair of bs34, they perform good but i always feel like the bike is missing something in the higher rpm range. How does the Kawasaki carb compare?

    And would anyone know if there is data from a dyno session available? If these carbs are better everywhere i might give them a try
  11. ippytattoo

    ippytattoo Just another grumpy old hack.

    When I got my bike it had bs34's that I eventually sent out to oldskoolcarbs for a proper cleaning and rebuild. Which, by the way, Rick does amazing work. They worked well but are not a modern carb and I have problems leaving things well enough alone. It was a sharp learning curve with jetting and such but thanks to the efforts of Mr Riggs we were able to establish a baseline jetting that is a good starting point. I haven't done a dyno session with them so can't comment on any kind of hard and fast numbers but by the "seat of the pants" dyno they perform very well throughout the rpm range once the jetting is dialed in for the particular setup they are tuned for. I havent actually weighed either bs34's or cvk34"s but the cvk"s felt lighter in the hand which is less stress on the intake boots/adapters. A win in my book. So in short I havent found a down side to the cvk34's. YMMV
  12. bikefreakjon

    bikefreakjon XS650 Addict

    I feel that throttle response is faster with the newer cvk carbs. I'm not surprised giving the more modern design and much lighter slide.

    This was confirmed seat of the pants style when my old boss took it out for a test ride and came back grinning. He said "I always thought those old mikunis made these feel sluggish"

    Top end wise, someone earlier in this thread mentioned that ninja 500
    s can make 70 hp.

    When I attached a digital tach, I was pleased to see that the power flattens off just before 7500rrpm on my bike with stock sportster mufflers and stock headers.

    To me that's ideal since I haven't got a performance valve train.
    Last edited: Oct 5, 2020
    Bjorn and gggGary like this.
  13. Bjorn

    Bjorn XS650 Addict

    Hahah, I suffer from this too!

    I am willing to give it a try if I come across a nice set for a reasonable price. The diaphragms on my BS34 are getting awfully thin any ways.... for the price of two new ones I can probably pick up a set of CVK. Bur first I need to find if there is a shop in the Netherlands (or Europe) that sell jets and needles.
  14. Bjorn

    Bjorn XS650 Addict

    O btw, is there a thread where most of this info regarding CVK carbs is summarized?
  15. bikefreakjon

    bikefreakjon XS650 Addict

    Lol, this thread!
    gggGary likes this.
  16. bikefreakjon

    bikefreakjon XS650 Addict

    My coworker is considered me to be pretty picky about exact carburetor tuning. I like things to be spot on if possible. One of the reasons that I reread this entire thread several times was because I was very interested in the aftermarket replacement needle profiles. And then I find to my surprise that the stock needles with us thin shim seem to work just peachy! Of course that's at my altitude on my specific bike and all that and I'm sure it could maybe be better but I am not sure how.

    also I have a quarter turn CR250 throttle on mine which might might make up for some sensitivity at very small part throttle openings since it acts a lot more like an on/off switch than a stock twist and grab twist and grab throttle.
    gggGary likes this.
  17. aldo5468

    aldo5468 Redleg XS650.com Supporter

    The amount of stress on the intake boots depends somewhat on whether any given carb set is supported at both ends or just cantilevered off the intake boots. I think the CVK's are lighter than the OEM Mikuni's - mine are attached just to the intake boots and seem to be just fine.
    gggGary likes this.
  18. 5twins

    5twins XS650 Guru Top Contributor

    I've never had any intake boot issues running either of the stock carb types with pods, but I have the tin "shrouds" in place over the intake boots. These add needed support. Run without them and you may very well have boot splitting issues .....

    aldo5468 likes this.
  19. Grimly

    Grimly XS650 Addict


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