Need to locate a HS carb idle jet

Discussion in '4-Stroke Engines' started by darwin, Aug 18, 2013.

  1. darwin

    darwin Well-Known Member

    49cc/Anyone know where to buy those without buying a whole carb? Mine works but it got boogered up when I was pulling it out. It was stuck in there pretty good. Like to get a spare for when I need it.

  2. HeadSmess

    HeadSmess Well-Known Member

    all my searches were in vain. not too sure about recently but.

    how badly boogered? if its working, it should be right :)

    as long as the jet itself is intact and the o-rings are good... wouldna worry.

    from experience ive found it best to have spare carbs complete...emulsion tubes, few jets to drill when repiping etc.. i got 4 sizes now :)

    havent found anything sold seperately:(
  3. BigBlue

    BigBlue Active Member

    I know ThatDax doesn't have them listed on their website, but it wouldn't hurt to ask Dwayne if he has any spares or maybe he could point you in the right direction.

    Good Luck,

    AKA: BigBlue
  4. darwin

    darwin Well-Known Member

    Forgot I had an old OEM gx50 carb laying on the shelf and took the idle jet out of it and put it in the HS 49cc carb and it works perfectly, idles like a champ. Had 2 put 2 new orings on it. I know you can probably buy that from a Honda dealer, can't be too expensive. Weird thing is the hole on the OEM Honda idle jet is about a 16th in diameter. The HS idle jet hole is in the 1000ths, Honda is way bigger and still works. Very strange, maybe i'm on to something here, maybe it'll run better. Find out tomorrow when I ride it and see wassup.
  5. jaguar

    jaguar Well-Known Member

    I think you have a regular NT carb that has no idle jet, only a main jet. The idle mixture is set by the needle height. Putting a bigger main jet on it of course will let it start and idle the same, since its size only comes in to play at top revs.
    my advice has always been and will always be: Get a Real Carburetor
  6. HeadSmess

    HeadSmess Well-Known Member

    um...jag...its a huasheng 49 cc 142 f or whatever. or a honda gx50 with a HS carb fitted.

    a 4stroke industrial carb for a fourstroke industrial engine

    they have a low speed jet, with airscrew, and a plain butterfly with standard jet. there is no needle. :(

    oh yeah, that low speed jet on the HS is tiny! was gunna pull out the guitar strings and measure it but thought "the thing runs ok" likes like it would be .25 mm or less!
  7. jaguar

    jaguar Well-Known Member

    what throws me is how it can run the same although the jet size was drastically different. My experience is that the idle mixture ratio is very critical and even a half turn on the air screw can make a significant difference. something don't add up
  8. darwin

    darwin Well-Known Member

    Rode the bike today for about 35mi and it ran perfectly, so I can say with experience the Honda idle jet does work with the HS carb on a Honda 50 motor. Even seems to be a slight improvement also. I'm happy.
  9. HeadSmess

    HeadSmess Well-Known Member

    its a 4stroker! it doesnt foul plugs if it idles for a long time ( as long as they arent chinese plugs!) even if its set so rich it sprays petrol out the pipe... tends not to accelerate too well though.

    its an interesting carb in how the fuel is first regulated via the main jet, enters a seperate section machined at the base of the emulsion tube. here, some of it is sucked up to the idle, the rest bubbles up into the emulsion tube and out the jet. as the whole lot fills up with fuel when not running, i guess it would give for a brief super rich condition when first started.

    the screw doesnt adjust just air, or fuel alone, but rather, a mixture that is then mixed in with the air bypassing the butterfly. it blocks the port off into the carb throat behind the butterfly. you can poke the tip of it when screwed all the way in.

    when the jets the right diameter, idle can be so low that the butterfly is completely closed, and all the fuel/air is delivered via the low speed system. the screw only adjusting the volume delivered, not the mix.

    otherwise its a matter of adjusting idle screw and mixture screw for a nice idle as they interact. in this case, air bypasses the butterfly, but doesnt create enough suction to draw fuel through the main spraybar. so this air is straight air. the idle system is delivering an overly rich mix as its jets oversize. you have to adjust the idle flow with the clean bypass flow, to get the correct mix.

    the biggest issue is when the orings around the idle jet get damaged, then the low speed circuit is too lean, and nothing will fix it but new orings. my theory is dont remove the thing!

    the struggle to fit a vm20 isnt worth it.

    a really odd ball bolt pattern that needs a pretty fancy adaptor to work.
  10. darwin

    darwin Well-Known Member

    The problem Headsmess with the HS idle jet the hole is small and the slightest debris will clog it up. That hole is so small a bread rapper wire won't go through it. Only thing I could find small enough to poke through it was a small brass wire off of a fine brass wire cleaning brush I had.
  11. HeadSmess

    HeadSmess Well-Known Member

    its less than 9 thou, anyway! finest string i have handy. why didna i stick with the 8's? :) never seen a drill that small!
  12. Stoltzee

    Stoltzee Member

    I just finished a complete cleaning of the fuel system. Had a bad O ring on the float bowl. Got an Oring, and little filter at lowes. Used guitar strings to ream,and opened that main jet a slight bit. Cleaned everything with carb cleaner, and put it back together. First time i pulled the rope it started right up, and I was able to open the butterfly completely, and it idled beautifully. I was able to adjust the mixture screw??? by smell. Definitely noticed a difference in acceleration.
    On these HS 49f's there's lots of post that advise opening that main jet a little.
    Cant wait to ride it tomorrow.