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Mikes keihin carb kit

Discussion in 'The Garage' started by bigpup, Sep 15, 2010.

  1. grizld1

    grizld1 Grumpy old man Top Contributor

    "...Better than any other Japanese carbs" says Lalonde. That statement includes Mikuni and Keihin dedicated 4-stroke pumpers, which makes it another false performance claim from the home of the "drop in" camshaft, the plugs that add 10 hp, and so on. The PWK is one more 2-stroke carb that can be modified for 4-stroke applications but will never fit the 4-stroke demand curve optimally. Anyone buying those had better know his business when it comes to tuning, because he'll get no tech support from Mike's XS, and you can't just bolt on performance carbs and go.
    XSsex50 likes this.
  2. bigpup

    bigpup XS650 Addict

    so the nice price comes with headaches, good to know thanks, for the input gizld.
  3. grizld1

    grizld1 Grumpy old man Top Contributor

    They'd be no more of a headache for an experienced hand to tune than anything else, really. But the knowledge base for the PWK's on our application is thin, and Mike's XS won't help. No doubt about it, that's a very attractive price, and we can hope the knowledge base will grow as those carbs get into the hands of folks who are skilled tuners and willing to share information.
  4. Jack

    Jack XS650 Junkie

    Flatslides rule regardless of brand.
  5. The PWK series is meant for 2 strokes as noted above. Yes, someone with experience in tuning could make them work but a set of proper 4 stroke carbs would be much easier to tune.

    Yes flatslides are best.... but the carb needs to match the application.
  6. Brew

    Brew XS650 Addict

    someone test these I need new carbs!
  7. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    I installed MikesXS XS Performance Keihin Carb Kit last night in my '81/H.


    The kit is complete with everything you need to do the installation. It's actually more time consuming to remove the old carbs than it is to install these babies!

    The engine started right up after installation. I did a quick sync by sound of the exhaust and off I went for a quick test ride. It was raining a bit so I did not do a very complete run, but from that brief run I can say that these carbs perform as advertised.

    I have the PAMCO "Ultimate" ignition installed, of course, and these carbs combined with the 82,000 Volts that that coil produces should be a great combination.

    Mike had these carbs custom made for the XS650, so they are not just an off the shelf carb that has been rejetted for the XS650.

    I will spend a little more time doing a more complete evaluation and report back.

    I should be able to tell you if Mike was exaggerating or not, but so far I don't think he was. You really have to try these carbs out and not pre judge them because they are not just an adaptation of an old design. They were custom made for the XS650.
    Last edited: Sep 28, 2010
  8. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    DAY TWO:

    Well, I'm not a carb guy. I do know that this particular version of the carb is only available through MikesXS.

    I think I am more representative of the average XS650 rider when it comes to carbs, and so far I am impressed from that perspective for these reasons:

    1. Kit comes complete with everything you need.
    2. Installation is easy.
    3. The carb works right away with the jets that it comes with.
    4. Carb syncing both at idle and WOT is easy. I used the dead cylinder method by removing one blind vacuum barb plug at a time and adjusting the opposite cylinder for 1,000 RPM. I also crossed the vacuum barbs to further smooth out the idle. Then I verified that both slides reach the top at at Wide Open Throttle.
    5. The kit does include two sets of jets, one richer, one leaner than the jets that come installed, but I don't think I will need to use them.
    6. Throttle response is instant, which I guess is typical of cable operated slides rather than vacuum operated.

    I'll be doing some more test riding and report back.
  9. KingL

    KingL XS650 Member

    Do they have accelerator pumps?
  10. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    No, they do not have accelerator pumps. That's the Dellorto PHF36 pumper's you are thinking about. The kit of two Dellorto PHF36 pumpers is $549.00 These Keihin's are $299.00 for two.
  11. Micah

    Micah XS650 Member

    Thanks for the review Pete! Mine wont be here until friday but man I can't wait to try these puppies out! I'm feeling much more confident in my purchase after reading this!
  12. Travis

    Travis Staff Member XS650.com Supporter

    Damn you pete! :wink2: UPS is supposed to be delivering my set today! I thought I'd be the first to review them and figured since I have stock BS34s, VM34s, and now these, I could do a little write up describing them all. Oh well, glad to hear they are going to preform as advertised. I also bought a sweet ultrasonic cleaner that I'm waiting for in the mail. I'll use that to clean the all the carbs for a good baseline.. I guess I'm not in so much of a hurry to do a review now, but I'll still try to get it done soon. :bike:

    Highspeedhamish, From my understanding, these aren't just any PWK carbs. They were modified, designed, and manufactured just for the XS650 so they are specific to the application. Very specific.
  13. Travis

    Travis Staff Member XS650.com Supporter

    I see Mike's got the dyno chart up.

  14. Tech7

    Tech7 XS650 Junkie

    Anyone know if they're linked? Wonder how they'd work on my GS450? It's got BS34's that pretty much suck ass.
    Last edited: Sep 29, 2010
  15. pamcopete

    pamcopete Ride.Enjoy.Life is Simple

    No, no...I'm holding back on my very positive comments about these carbs because I want someone else to report the same thing.The really spectacular characteristic is the tremendous torque that you get when you open the throttle. It doesn't exactly do a wheelie, but the front of the bike lifts up like I've never experienced. You are up to 6,000 RPM before you know it!

    So, install them ASAP and let us know if you agree with my experience so far. I am going to do a mileage check on Friday morning.
  16. bigpup

    bigpup XS650 Addict

    thanks pete, the review helps
  17. Brew

    Brew XS650 Addict

    can't wait to see numbers next to vm34's Travis
    Last edited: Sep 29, 2010
  18. grizld1

    grizld1 Grumpy old man Top Contributor

    Dyno numbers don't tell the whole story. The problem with refitted 2-stroke carbs on a 4-stroke engine has to do with leaning out in hard midrange throttle transitions once the main circuit is dialed in right. In Keihin, Mikuni, and Dell'orto aftermarket 4-stroke carbs this is dealt with by using an accelerator pump. No modification to the basic design of the PWK is going to eliminate the issue, and so far I've read no specifics on what those modifications amount to.

    That's not to say that the PWK's, cable-top Mikuni TM's, or Mikuni VM's, all of which share that basic issue, are bad carburetors, won't give good service, or can't deliver more power and faster throttle response than OEM BS-series carbs--they can, and when properly tuned, they do. But a phrase like "the best" covers a lot of ground. Among low-end aftermarket carbs, the XS Performance PWK kit may turn out to be the pick of the litter in street applications; but that's as much as should be claimed for them.

    Pete, thanks for the review; it's good to know that the kit comes with some extra brass, that's a nice touch. Travis, I'm looking forward to your comparison to the VM34's.
  19. pamcopete

    pamcopete Ride.Enjoy.Life is Simple


    Well, I will graciously concede home field advantage to you when it comes to carbs, but in this particular case, there is no point in including this carb in with the others because it is not comparable anymore with the mods that were done for MikesXS. It is a 32mm Keihin Flatslide PWK in name only. If you went to the factory and ordered up a 32mm PWK, you would not get this carb. It is available exclusively from MikesXS.

    As for the extra jets included in the kit, they will probably not be used for most applications, so other than syncing the carbs, there is no tuning required.

    The carb was developed over a three year period by Heiden Tuning, and the mods are proprietary. I don't even think that it would work in a 2 stroke engine anymore, maybe that gives you a clue as to the mods.

    It would be nice if you could actually experience this carb and then give us your opinion, which I'm sure would be objective and helpful.
    Last edited: Sep 29, 2010

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