new carburetor

Discussion in '2-Stroke Engines' started by jaguar, Jan 1, 2015.

  1. jaguar

    jaguar Well-Known Member

    There was mention recently of a new style carb with a fuel delivery column raised up into the venturi like the Dellorto SHA carb but with adjustability. I was too busy to record the carb name for further investigation. Can anyone please tell me the carb name and/or their web site?
    I believe that is a superior design because multiple small "main" jets should atomize the fuel better than just one, as a normal carb has. When I put on a 12mm SHA it ran better, had more power, and higher top speed although the venturi flow area was smaller than the stock carb. Its lack of adjustability was its downfall when I moved down from the mountains to the beach.
     

  2. darwin

    darwin Well-Known Member

  3. jaguar

    jaguar Well-Known Member

    yes the jet column sticks up into the throat and the gasoline comes out of multiple jet holes when the slide is fully raised.
    great idea but it needs to be fully adjustable like any good carb, allowing adjustment of the idle, mid-throttle, and full throttle mixture.
    from what i read the new carb does that but I need its name so I can look it up.
     
  4. darwin

    darwin Well-Known Member

    From the link I posted. "Dellorto sells a good adjustable carb, the 16mm PHBG for $95, and it is fully adjustable unlike the SHA models."
     
  5. darwin

    darwin Well-Known Member

  6. jaguar

    jaguar Well-Known Member

    You are quoting me since that is my site.
    yes the PHBG is fully adjustable but it doesn't have the vertical jet column like the SHA does.
     
  7. darwin

    darwin Well-Known Member

    Oops, nice site there.
     
  8. darwin

    darwin Well-Known Member

  9. jaguar

    jaguar Well-Known Member

    close but not quite what I am looking for.
    What pedalchopper is offering is just an SHA copy. I don't know why they are lying and saying it has extra adjustability. Lies are more profitable than honesty I guess.
     
    Last edited: Jan 3, 2015
  10. darwin

    darwin Well-Known Member

  11. jaguar

    jaguar Well-Known Member

    it could be a plunger like the Bing carbs have. you push it down and it pushes down on the float and that lets more gas in so you can kickstart the engine with richer carburetion, an alternative to a choke.
     
  12. jaguar

    jaguar Well-Known Member

    APT SmartCarb
    25mm $450
    www.powerapt.com

    High Atomization
    The extremely fine fuel atomization provided by the SmartCarb exceeds that of Electronic Fuel Injection, which is a result of the SmartCarb's proprietary venturi shape and features that are designed to accelerate airflow past a precision flat-ground fuel metering rod. This highly accelerated airflow results in a strong signal to the metering rod which produces fuel droplets that are much smaller and more highly atomized than the fuel droplets produced by modern EFI systems and other conventional carburetors.

    Ultra fine atomization means a more complete and significantly cleaner combustion burn, resulting in lowered emissions, greater fuel economy and increased power. By effectively atomizing the fuel prior to combustion, more of the fuel is consumed during the combustion process. In addition, smaller fuel droplets mean more of the fuel's potential energy is released during combustion, leading to an increase in power. Extensive testing utilizing dozens of engines has yielded a minimum power increase of 5% and as much as 14%.

    Easy Adjustability on the Go
    SmartCarbs are highly, yet easily adjustable via the mixture adjuster on top of the carburetor and the idle adjuster on the side. Both adjusters are readily accessible by hand without having to remove the carburetor from the engine or even getting off the bike. Making mixture adjustments is as simple as turning the engine off, opening the throttle all the way and pushing in and twisting the adjuster to make fine mixture adjustments. And because the SmartCarb compensates for ambient air density, once the right mixture adjustment setting is found, you can leave it alone and the SmartCarb will do the rest, regardless of altitude or air temperature. No more messing around with jets!
     
    Last edited by a moderator: Dec 15, 2015
  13. boyntonstu

    boyntonstu Member

    This is another possibility:

     
    Last edited by a moderator: Dec 15, 2015
  14. Arty

    Arty Active Member

    Do you guys have any opinion on the Walbro Stage3 carbs?
     
  15. jaguar

    jaguar Well-Known Member

    It's hard to regulate a vapor carb which is why there are no factories making them.
    Walbro is good but requires some DIY to install them.
     
  16. boyntonstu

    boyntonstu Member

    It is worth a try for us DIYers.

    After all, most of us don't buy our bikes ready made.
     
  17. darwin

    darwin Well-Known Member

  18. jaguar

    jaguar Well-Known Member

    very interesting.
    but at full throttle the slide is all the way out of the flow path, unlike their drawing, and so I think this product would have zero effect at full throttle. Possibly at lesser throttle positions there may be better atomization which would give better power when slowly cranking the throttle open when accelerating. I think it would require leaner jetting from the needle which is hard to do on all carburetors. Maybe some company should make their own carburetors incorporating this idea, with their own jets.
     
  19. jaguar

    jaguar Well-Known Member

    Here's what was said on the "Cafe Husky" forum by a guy with a single cylinder 430occ Husqvarna MX bike.
    As I predicted the needle jetting had to be leaner. This guy did it by drilling a hole in the shroud that sticks up into the flow path in front of the needle jet opening which relieves the vacuum at the jet, therefore making it leaner.

    "I spoke with Lonn (designer) He advises that the 1.5 - 2 hp per 100cc is based on multicarb, multicylinder 2 strokes (Snowmobiles with greater port swept area). A 70-80's single cylinder 2 stroke can expect .75 -1 HP per 100cc after jetting changes. Almost all increase is in low to mid range. Most comments reflect the perception of instant throttle response and bottom end drive. He suggested that the "Dial-a-jet" is a good companion as it targets top end performance."
    "I took it for a ride after a short warm up and noted that there is indeed a crispness in throttle response that was not there before, but it is too early to say if is worth it yet."
    "The last reported pilot jet was one that had been soldered closed. It too proved to be too rich after full warm up. The next step in the installation guide is to drill an air bleed hole in the needle jet hood [which would lessen the vacuum on the needle jet]. So… because I was less than confident this would be race worthy on July 19, I went to Cycle Gear and ordered a new Q-8 needle jet from Parts Unlimited in case I need to go back to the original jetting. I then used a #55 drill to place the air bleed hole as directed on my current Q-8. I was very close at this point but a little lean. I reinstalled the #15 pilot jet and it’s back to too rich. Drill out the air bleed in steps #52, #50, #47 testing each time with the #15 pilot jet. I am now about right and I have a functioning airscrew for air density adjustments at the track.
    Performance testing on the street or just ****ing off the neighborhood?
    The claim is more low-end and mid-range performance, with .75 to 1.0 HP increases per 100cc of displacement. I can say with certainty that it sharpens throttle response. My feel is that the performance increase is throttle position sensitive in the low/mid RPM range. I can feel a difference in roll-ons and part throttle operation, but at full throttle it is about the same as before. This makes it better suited for off road use (IMHO) because Mxer’s tend to spend their time at one of the two extreme positions (On or Off) Still, may be of use on those sweepers.
    A shared thought here on the limits of perception, I recently changed the porting on my 430 with the result of more felt low-end power and a big mid-range hit that was not there before. As a result, I cannot honestly say there is an improvement once I make it to the mid-range hit because if it is there, it gets lost in the crowd.
    I hope to make it to the track on Sunday for some final testing and assessment.
    Is it worth it?
    I am going to say yes subject to further evaluation at the track. I am done or near so and there is a performance improvement. $30.00 does not seem like much to pay for ponies these days and I enjoy a personal project.
    BUT… This is not a mod for the beginner. I spent at least 8 hours on this. I lost count of the times I removed, modified, installed and tested the carb. It is not “Plug and Play” by any estimate. I have a lot of experience and a machine shop at my disposal. Let the uninitiated beware.
    I did at last make it to the track on Sunday. I had left the fuel tap on from the night before and when I got to the track the bike was very flooded. After a lot of cranking and pushing, it finally started and I was able to blow it out. I didn't think to do anything else but ride and began to make 5-6 lap sessions. After a few sessions I checked the plug (old) and it looked good but slightly lighter than before. I felt the bike was hard to hot start and tried a couple richer pilot jets. That was the ticket. With a #25 pilot the bike would start on the 1st or 2nd kick both hot and warm. I should note here that means I overshot the sizing on the air bleed hole. So if I had a "do over" I would stop at the #55 drill hole and head to the track for final setup.
    As for perceived performance improvement on the track. It is difficult to tell. Big hits felt on the pavement vanish into wheel spin in the dirt and small improvements?...I think I can feel a bit more just as I open the throttle.
    I'll say again, A lot of work and technical savvy required for installation and setup.
     
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