Where to get larger main jet for stock HS carb?

Discussion in '4-Stroke Engines' started by lemont1, Jan 25, 2011.

  1. lemont1

    lemont1 Member

    I changed the air filter on my latest bike from stock to the one from sick bike parts. Now have too much air for the size main jet (found this info on this forum, thanx guys:bowdown:) so I went back to stock filter till I can re-jet. Thought about re-sizing with small drill bits one size at a time but am not really sure. Can some one recomend a place to buy maybe a set of different size jets for the huasheng 142 F stock carb? Thanx in advance for any help!

  2. gothicguy64

    gothicguy64 Member

    try spooky tooth
  3. sick bike parts has 10 different jet sizes for the regular old NT carb...
  4. Htown

    Htown Member

    was told that no such jet exists, and that you would just have to live with opening up the idle screw as much as you can without it dropping out. I guess that is why some sites sell extras.
  5. Silvaire

    Silvaire Member

    This is an OLD motorcycle racer tuning trick - an EMERGENCY method used in order to have the correct size jet when you just cannot obtain one.

    To increase the jet size, you can drill out a jet with the next size larger NUMBER drill.
    (If you EVER drill out a jet, mutilate the number stamped on it so that no one will later confuse it with an unmodified jet.)

    But what to you do if a jet is too large?

    Get some flexible insulated stranded copper wire. Poke one or more strands of wire through the jet until you get the engine running right. Secure one end of the wire by wrapping it around the top of the body of the jet (or whatever else is in the area may be handy) and then poke the loose end through the jet. Not all stranded wire has the same size strands, so find wire of a size where each strand of wire will reduce the cross-sectional area by only one percent or so. (Measure, and then use a little math here.)

    I know that this sounds like a REALLY funky idea, but I have successfully used it many times.
    (I have occasionally used it as a "semi-permanent" solution - holding the wire strands in place by soldering them to the top of the jet after finding the correct number of strands to use.)
    Last edited: Jan 28, 2011
  6. 4950cycle

    4950cycle Member

    What to do ?

    I like the wire strand idea. But what do you do when you have the needle on a motorcycle carb going down through that hole in a main jet as the carb piston/plunger/slide goes up and down ? It will jam against the side wall of the main jet. How do you get around this ?
  7. Old Bob

    Old Bob Member

    You really don't want to drill the jets. Drilling can leave spiral marks in the hole which will creat turbulence that can actually reduce flow volume.

    The holes should be reamed with a straight flute reamer.
  8. 4950cycle

    4950cycle Member

    I have a 1978 750 parallel twin (side by side) with twin carbs. It was made in the 1970s gas crunch. The first one ya know ! Soo Kawi wanted to boaste great gas milage for this bike. So as a result they jetted it way lean. The end result being, most of them went to an early grave because they ran hot as a result of being air cooled an mainly always running lean. They didn't make a whole lotta jets for these big twin carbs so finding richer (bigger hole) jets was hard. Anyway, to make a long story longer,lol I drilled my two main jets one" number drill " larger then the original size of the jets as Silvaire indicated above. Needless to say I have one of the only 1976-1979 (only years they made this model) Kawi 750B model that runs great in the US. The Britts seem to have a lot more Motorcycle savy / machanical guys so they have more that run right. Bottom line, Drillin jets works ! Just go no more than one number drill at a time. It is easy to over do it so be patient. Cheap fix if lean is your problem.
    Last edited: Feb 22, 2011
  9. lemont1

    lemont1 Member

    I added two wire strands with no problems so far and no real plans of changing any thing cause, well, if it aint broke dont fix it, right? When I drilled the jets I ran the bit from both sides and turned clockwise while pulling the bit out, thinkig that this would reduce any rifleing (if that is the right term) and as I said It works so far.
  10. 4950cycle

    4950cycle Member

    I believe rifleing would be the perfect word for it. I don't believe it would matter anyway. Unless it was so eregular you could almost see it with a 20/20 naked eye. Were not talking nuclear reacters or rocket science. We are talking little Industrial internal combustion engines. As long as the air / fuel ratio is somewhere around 14 to 1 and the timeing is where it should be and ofcoarse spark it WILL run gauranteed. As long as you are in an atmosphere like earth has period.
    Last edited: Feb 22, 2011
  11. HeadSmess

    HeadSmess Well-Known Member

    wire in the jet? i have never ever thought of that or heard of it, i alway just solder filled n redrilled...

    sounds perfectly feasible.

    especially on the 142 hua... has no needle :) might try it next time i need to...
  12. lemont1

    lemont1 Member

    Is there a good replacement for the stock carb on the HS 142? mine is running good But I would like to be able to change the jets when I travel ( I take my bike with me to Utah) and it doesn't like the elevation change.
  13. 4950cycle

    4950cycle Member

    Another day I learned something

    Thanks Headmess , I will put that little soilder idea in my jetting trick bag thank you.
  14. tjs323626

    tjs323626 Member

    The wire in the jet is used by some of the go cart racers. They say it's the way to fine tune the perfect fuel air ratio. It should work fine on these small 4 strokes too. Just make certain it stays in the jet and doesn't get pulled into the engine.
  15. 4950cycle

    4950cycle Member

    If you can use copper wire strands (if you can even find it anymore).lol It is softer than steel and I think aluminum. If it goes in you engine, It might not lunch it out. It will just poop it out the other end.lol
  16. ocscully

    ocscully Member

    Honda Main Jets?

    I bought a Mikuni VM-18 carb cheap and made a manifold to mount it to my Honda motor and then realized that the 18mm was larger than the opening in the block of the motor, so the project has come to a stand still. I've been watching/looking for a Mikuni VM-16 cheap but have not come across one yet. Honda makes/lists four different size main jets for the GXH50 in their parts manual. they range in size from a #48, #50, #52, & #55. My motor which was purchased from Small Engine Warehouse several years ago came with a #55 main jet. If I'm remembering correctly it measured .021 These Honda jets would very likely fit into the HS carb? Seems to me that they run around $9.00 apiece from the local Honda Small Engine Shop (Republic Engine) here in Orange County.

    Last edited: Feb 25, 2011
  17. Htown

    Htown Member

    There is a vendor out of Florida who sells the jets. Was wondering if the smaller jet designation meant more flow of gasoline? as I am starved of gasoline. will look into honda engine shop
  18. ocscully

    ocscully Member

    Mikuni VM18 Photos

    Found some photos of the Mikuni VM18


    Attached Files:

  19. 4950cycle

    4950cycle Member

    No I don't believe so. It is not like the gauge system. Where the lower the number the larger the object or cavity. Jets go the higher the number the bigger the hole in the jet. Wich translates into more gas delivery to the air flowing by down the carb. thraot.
  20. lemont1

    lemont1 Member

    Thanks ocscully, I will visit the local Honda shop this weekend. I would just like to have an assortment of jets to keep in my tool bag since I have two bikes with the HS engine.