carburetor/throttle upgrade. oh yes, i went there...

Discussion in 'Performance Mods' started by gone_fishin, Jul 13, 2007.

  1. gone_fishin

    gone_fishin Guest

    i think i may have stumbled upon the sophisticated grandpappy of the "happy time" carby.
    this is uncannily a 1978 honda express. matter of fact, it's so close i'm betting it'll work. carb w/choke, throttle w/choke, brake lever, killswitch, brakelight. what a tweak this is gonna be if i can pull it off.
    like the "happy time" it has a mechanical idle-screw. it has a choke that (i think) affects only idle, an idle-mixture screw, & i'm
    guessing it has mixture slots on the needle, too, because i can see the circlip. if i'm figuring this right, the express needed a LOT of rpm's to do 30mph, so i bet flow is already adequate, i'm not adverse to punching out the jet tho as last resort.

    now that the chain tensioner is working right, i need something to do in the morning, so i'll tear it down and have a look.

    at the very least i'll have a neat throttle assembly 8)

    any info would be groovy :)

  2. iRide Customs

    iRide Customs Member

    Hmmm...that looks interesting. Are you going to bolt it right to the cyl. or will you need a new manifold? If you need a new manifold, I know someone who could make one for you :grin:
  3. gone_fishin

    gone_fishin Guest

    it's almost the exact size as the stock carb, so bolting direct to the cylinder would jam it into the clutch cable.

    first i'll just rig something up until i know it works, then we'll talk to your "friend" about a manifold, i hope he works cheap :wink:
  4. gone_fishin

    gone_fishin Guest

    wavygravy showed up just in time to run-get-me a piece of heaterhose & take some pics :)

    will it?
    it sure will!
    :evil: :evil:

    i'll keep yas posted 8)
  5. srdavo

    srdavo Active Member

    looks good.....what does the 2nd carb cable do? choke?? nevermind.... I see the choke lever on the grip.

  6. gone_fishin

    gone_fishin Guest


    i have 187 miles on a roller-bearing "70"...running penzoil at's starting to kick in really nicely.

    the happy time carb: predictable starts & reliable. sorta decent scoot up to 19-21 and it gets a bit flat...if i hold it at 90% throttle i eventually get 26-28mph on the level.

    the ???shin carb: hard start, excellent scoot up to 20mph, then i have to feather it around 75% throttle but i get a strong 28mph cruise...this can only get better when i make a real intake and learn how to set it.

    any advice or guidance on this carby?
  7. azbill

    azbill Active Member

    lookin' good dude ! :D
    man, you got 2 threads on the go here...
    kewl :lol: 8) 8) 8)
  8. gone_fishin

    gone_fishin Guest

    you know, 'kronic, i never thought i'd be messing around in here at all :lol:

    ok, back to the happy-time carb for now...i'll have to work on an intake & really get the new one clean and functioning right.

    the honda throttle cable & cap fit right on the happy-time carby, too easy :)
  9. gone_fishin

    gone_fishin Guest

    and i'm still goin' there!

    a buddy offered to weld whatever i could come up with...waste not, want not ;)

    Attached Files:

  10. azbill

    azbill Active Member

    that should work pretty good !!!
    should work a lot better than last time you tried it
  11. good work there
    i was thinking of using radiator hose so i could tilt the carb for flashy air filter
    i have a third of the area to work with
  12. gone_fishin

    gone_fishin Guest

    that heater hose i used was only a temporary test, a way tight fit...i think what would be better is that green stuff used for emission tube repair, very durable material and high-heat resistant.

    i can't wait to try the custom intake, i bet it rocks...i can't use it with the current engine, but my original 70 is waiting to reclaim it's rightful place in the frame...maybe just in time for a run up to whidbey island.

    i see you guys didn't notice what i used...i have the only kit in the world that didn't have a "FREE! large frame adapter" but a "FREE! intake adapter" instead :rolleyes:

    Attached Files:

  13. gone_fishin

    gone_fishin Guest

    it worked, but it didn't...not enough flow, end of that story.
  14. minibiker

    minibiker Guest

    did that carb work out for u???
  15. gone_fishin

    gone_fishin Guest

    nope, not enuff fuel on any setting. it was fun trying, tho :)
  16. 5-7HEAVEN

    5-7HEAVEN Guest

    :cool:methinks it's your "exotic" manifold.:shock:

    once you get that down, power should at least return to normal.

    or you could jet richer first.
  17. gone_fishin

    gone_fishin Guest

    shoot, it was free, the intake is smoother inside than stock. i tweaked the needle to the 5th dice, it's just to small to apply.
  18. stinger48

    stinger48 Guest

    if it came off a 50cc honda it should run a 50cc happy times motor, just take off the bowl and remove jets and clean with air compresser check that floats are set correctly and that the needle and seat under the floats are not blocked this fixes most carby problems , also if the diameter of the venturi is the same as the happy times carby its just a matter of jetting to get performance just go step by step if to rich it will not rev out
  19. gone_fishin

    gone_fishin Guest

    ahhh, i should have mentioned the venturi tapers to a very small size at the slide, it was choking the engine. my bad for not being clear on the "why."