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Thunder Power Jet

Discussion in 'The Garage' started by ReycleBill, Oct 31, 2019.

  1. ReycleBill

    ReycleBill Part Time Tyrannicide XS650.com Supporter

    It seems the boat and snowmobile guys have known about these things for years. Even S&S offers a version for the Harley riders running S&S carbs. And perhaps I'm the last person in the world to learn about the Thunder Power Jet which according to the manufacturer, not only provides additional fuel at full throttle but also "gives you a range of over 10 to 12 jet sizes with precision external adjustment" with no tools needed.

    Anybody ever use such a thing?

    My riding sometimes takes me from sea level to 5,000 altitude in a single weekend. It's impossible to jet for that. Might something like this solve my problem?
  2. 5twins

    5twins XS650 Guru Top Contributor

    Our CV carbs are pretty forgiving and somewhat altitude compensating. I don't see the need for that thing.
    gggGary and jetmechmarty like this.
  3. jetmechmarty

    jetmechmarty XS650 Guru Top Contributor

    I've done lots of riding between 200 and 6,000 ft. The CV carbs seem up to the task to me. I don't believe I'd mess with any such thing.
    gggGary likes this.
  4. Jim

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

    Yeah... if I remember my history correctly, one of the main reasons CV's were designed was to make a carb that was better at altitude compensating.
    gggGary likes this.
  5. XSLeo

    XSLeo XS650 Guru Top Contributor

  6. peterg

    peterg XS650 Addict XS650.com Supporter

    What about using this with VM carbs? Looks like a VM on the thunder power jet website.
    gggGary likes this.
  7. gggGary

    gggGary Stop that! Top Contributor XS650.com Supporter

    :twocents: Suspect it will cause more problems than it "fixes".
    Mailman, grizld1 and Jim like this.
  8. grizld1

    grizld1 Grumpy old man Top Contributor

    No, Bill, you're not the last guy to learn about Thunder Products. I actually ordered one of those "Power jets" a few years ago just to have a look at it because the ad story made my bullshit detector spike (mystery scientist markets miracle performance boosters through obscure snowmobile shop, instead of selling rights to the big boys for the big bucks). The look was as far as it went. I wouldn't bet on it, but that stuff might work on a 2-stroke motor. I sure wouldn't try it on a 4-stroke.
    gggGary likes this.
  9. solo2racr

    solo2racr Suck, Squeeze, Bang, Blow

    "Power jets" were an idea used in the early '80's on highly tuned 2 stroke roadrace bikes. They were to keep the engine from seizing when the rider over revved the engine and fuel demand from the extremely ported engine went beyond what the main jet was able to deliver.

    And yes.......Mikuni VM style carbs are what they are meant for.
  10. grizld1

    grizld1 Grumpy old man Top Contributor

    Power jets are still a feature of Mikuni TMX series dedicated 2-stroke carbs, if I'm not mistaken.
  11. ReycleBill

    ReycleBill Part Time Tyrannicide XS650.com Supporter

    I've also noticed that .Mikuni sells their own line of power jets that can be added to.Mikuni CV carbs.

    This statement by Thunder Power Jet manufacturer also go my attention:

    "With the Thunder PowerJet installed, the main jet is decreased by 20% to 25%. The remaining fuel is supplied by the Thunder PowerJet. This combination gives you great throttle response due to the smaller main jet’s superior atomization. Throttle response is dramatically increased. Overall power is also increased for several reasons. First of all, the Thunder PowerJet can be dialed in so quickly and accurately for any temperature or altitude that you no longer dread rejetting your carbs. It is about a one to two minute job. With the Thunder PowerJet, fuel distribution is enhanced because you are now adding fuel in two locations instead of just one. The last benefit is increased fuel efficiency. This is due to part throttle riding conditions where you are running on the the smaller main jet."

    I'm also wondering if power jets might solve the problems caused with 2-1 intakes running a 38 round slide .Mikuni carb or other single carb.

    I realize several people said that CVs are great with altitude changes but in 15 years of owning my '83XS with CV34s I have never found a jetting that would take me from Wilmington, NC. to Mount Mitchel, NC (less than 400 miles) without acting up on one end or the other.
    GLJ and gggGary like this.
  12. grizld1

    grizld1 Grumpy old man Top Contributor

    The link specifies use on VM carbs, doesn't mention BS series vacuum pots. Give it a try, yours would be the first user report I've seen on a 4-stroke motorcycle application, and I might wind up eating a big plate of crow.
    gggGary and GLJ like this.
  13. solo2racr

    solo2racr Suck, Squeeze, Bang, Blow

    I wouldn't bother with them on a any 4 stroke, and any XS doesn't even come close . The "powerband" of a 4 stroke simply does not swing high enough to justify their use. Most people have a hard enough time getting their jetting correct. Let alone adding another circuit that will influence one or more of the other fuel circuits.
    GLJ likes this.
  14. Jack

    Jack XS650 Junkie

    You might be off in your jetting on the CVs. I have Mikuni 38MM flatslides on my BMW R/90S and I have no carb issues going to M/M,etc. Power Jetting works from 3/4 to full throttle and I doubt you'd be traveling at the speeds on the BRP. If you want power jetting get a set of Lectron carbs(spelling).

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