350 cc big bore kit for KLX250, Ready to ship!!

Discussion in 'Vendors' started by Bill & Jo Ann Blue, Nov 11, 2008.

  1. MrFurious

    MrFurious Been here awhile

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    From what little I've read on Kawasaki Forums you need a JuiceBox or Power Commander with a custom fuel map. Those who have done it (mostly in the Philippines) report that the stock fuel injector seems to be up to the task at stock fuel pressure, so no need to upgrade the injector or pressure regulator.

    Here's a link to a thread about a programmable ECU that's available in Thailand.
    http://www.kawasakiforums.com/forum/klx-250s-71/stand-alone-tuning-ecu-klx250-36083/
  2. danceswithcages

    danceswithcages Been here awhile

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    Any word on Bill's new web address??

    I've searched the web and can't come up with any info on where to buy his kit.

    I'm seriously considering a KLX250 as my next bike, but only if the 351 kit is still available.
  3. IDRIDR

    IDRIDR Take me to the River

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  4. danceswithcages

    danceswithcages Been here awhile

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  5. tony.bike

    tony.bike n00b

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    Did you get your 351 kit yet danceswithcages? I am just getting ready to install mine. Looking forward to seeing how this all works out.
  6. xxaarraa

    xxaarraa Adventurer

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    OK, I read all 10 pages but still have an elementary question. The 22HP shown on the dyno - I am assuming that is at the wheel correct? Cannot be at the crank? I mean, stock bike makes 18 HP so I would hope the 351 kit nets more than 4 HP.

    Can anyone please confirm?
  7. Stumpy Pete

    Stumpy Pete Semi-Regular Guy

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    I see the dyno chart, and I agree that the 22hp seems a little weak. I think the point of the big-bore kit is more low-end torque than high-end power.
    I think it's interesting that the 351 makes within 1 ft.-lb. of max torque at 3750 rpm. I also think it's worth noting that the chart is for a bike with the 351 kit, but with stock exhaust and stock carb.

    I'd be interested in an incremental series that charted the benefits of the Mikuni carb and an aftermarket or KLX300 exhaust. It'd be nice to see a chart for a stock KLX250, too, but I realize dyno runs aren't free.
  8. Danger4u2

    Danger4u2 KX500 is Danger4u2

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    I took my bike to Bill Blue and he did my conversion. His 351cc kit/ pumper carburetor, my supplied full FMF Q4 and KLX snorkel. I've put about 4,000 miles on it without any problems. Don't know what the horsepower is but I really enjoy the KLX now. It's my go to fun bike. I did drop one tooth on the front sprocket for more low end, runs comfortable at 55 mph but it will still do 70 mph for short bursts.
  9. Stumpy Pete

    Stumpy Pete Semi-Regular Guy

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    The short answer is yes, the 351 bore kit alone will get you roughly five hp and five ft-lbs.

    Stock: 19.30hp, 13.12 ft-lb
    [​IMG]

    With big-bore kit: 24.58 hp and 18.75 ft-lbs
    [​IMG]

    More power and torque is available with further modifications.

    http://www.kawasakiforums.com/forum...1-big-bore-kit-review-38943/page2/#post482824

    I like that much of the gain is available between 4000 and 5000 rpms. I haven't done any of this yet, but I'm thinking about starting with the piston and cylinder and possibly doing the pumper carb later.
  10. corvettechris

    corvettechris Adventurer

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    We just finished a 351 upgrade on our KLX250.

    Here is our experience and recommendations for anyone contemplating this upgrade.

    We are at 4,500 feet so our jetting and power issues I bet are different than most. When we're riding the mountains at 5000+ feet, the stock KLX just wasn't doing it. Often struggling to maintain 55 mph on uphills. That is with a light rider even and with the dynotjet jet kit. So we decided it was time for MORE POWER CAPTAIN!

    We started with the Bill Blue 351 kit. I've done several car and motorcycle rebuilds, and had already adjusted the vales on the KLX, so it only took me an hour to disassemble the bike. Putting it back together took me about 4 hours.

    I changed the jetting up two main jet sizes as Bill suggested. It wasn't enough. But we were already a bit lean due to the elevation. Right now we're running a 128 (which is now a bit rich, I'll get to that later). We rode 100 miles to break it in a couple of days later. We could tell that it had quite a bit more power and we gained 10 mph top speed, with the only change being the 351 and jetting. I felt that the bike was still overly plugged up with the stock exhaust, so we ordered the FMF Q4.

    We received the Q4 and did the install in 10 minutes. What a huge change. Now the bike has a heck of a lot more power everywhere through the range. And now, with stock gearing it makes 90mph!

    Now, with the new pipe, its a bit rich and needs leaned out a little bit, but it is running great. I am not of the opinion that the carb itself needs to be changed. My best friend has been semi-professionally drag racing bikes for years and he agrees that the carb should be fine.

    Overall, this upgrade cost about $1,000 which is a lot, but doing it in stages made it more palatable.

    A friend of ours has the same KLX and I was telling him yesterday, I think the way I would recommend it now to anyone considering the upgrade is, buy the Q4 (with a quiet core) first, then see how the power is, then if you need more, do the 351 upgrade.

    __________

    Next up: LED headlight, black and blue plasti-dip paint job
  11. Roadstergal

    Roadstergal Can't touch the ground.

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    I'm interested in any additional reports of long-term longevity with the 351 kit, particularly with the stock re-jetted carb.
  12. mel brooks

    mel brooks Dirt Chick

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    3 plus years with 351 and stock re-jetted carb with 2 Brothers pipe.

    It's a supermoto that gets it neck wrung pretty good every time I ride it.

    Runs beautifully.
  13. Joeboblglt

    Joeboblglt Adventurer

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    Ready to pull the trigger on a 351 and carb from Bill. Those of you who have dealt with him/know him, is it best to email or call? Or does it matter? And, thanks for the posts and information you all have put here.

    Joe
  14. corvettechris

    corvettechris Adventurer

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    I would do both. Call him and talk about your plans and then email confirmation of when he said you could expect it. I found the calls to be necessary.

    Btw, someone else asked about long term testing on a 351 with stock carb. We have ridden ours almost 2,000 miles now. Sea level, 10,000 feet, through a decent amount of Alaska as well. It has taken some jetting changes, obviously, and we do find we are occasionally able to starve the carb of fuel. But it is at 80 mph and fairly high sustained rpm. It will just do a slight stutter.
  15. IDRIDR

    IDRIDR Take me to the River

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    Agree. Phone first, then follow-up with an email. Bill is a good guy to talk with. Do you have an aftermarket silencer? He has one of those too if not.

    I used the stock carb on 351 for several thousand miles and now have a TM36-68 pumper. Accelerator carb is a nice improvement for trail riding. If I were not trail riding (e.g. mostly street, forest service roads, easy DS), I'm not sure the pumper would be worth the cost if my budget were tight.
  16. Joeboblglt

    Joeboblglt Adventurer

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    Thanks IDRIDER and Corvettechris for the quick replies and the good advice!

    So I'm running an FMF Mega header and a Power C 4 exhaust package. I have the KDX snorkle and a Uni filter. All is properly jetted for now. As much as I love tight trails, I find that I'm doing less and less of the slow technical stuff and more of the faster stuff including some pavement. It sounds like I ought to try out the 351 with the stock carb (properly jetted of course) first?
  17. IDRIDR

    IDRIDR Take me to the River

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    I my opinion, yes. The stock carb does very well on the 351. Some will argue you won't be getting max possible power but if you're happy with it, is that a problem? The pumper carbs shine with their improved throttle response, mainly giving you a quicker acceleration from low rpm up due to 1) the stock CVK carb being slower to respond which is just its inherent design and 2) the pumper carb squirting fuel in while the slider is being pulled up preventing a lean bog out. If you need the quick throttle response, think pumper. If not, the stock isn't bad at all.
    Bill will likely suggest bumping up once size on the pilot and one or two on the main jet.
  18. Danger4u2

    Danger4u2 KX500 is Danger4u2

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    I took my bike to Bill and had him do all the work.
    351, pumper carb, I supplied the full FMF pipe.
    Back when I owned the bike I weighed in at 275
    wearing full off road gear. I used that bike hard,
    properly maintained but built to be ridden.
    No problems with the bike for 3000 miles.
    The guy I sold it to rides with us on occasion,
    still going strong.
    Go with the pumper carb, you will NOT regret it.