4 Stroke carburetor

Discussion in '4-Stroke Engines' started by stowaway, Aug 6, 2007.

Tags: Add Tags
  1. stowaway

    stowaway Guest

    I got a Grubeeinc 4 stroke vee mount kit.

    Just need some info on the carby.

    Where is the Choke? And im assuming the screw in this picture is the fuel/air mixture. Does anyone know the recommeded setting for the air/fuel mixture? (ie 3 full turns outwards. or something)

    is this right?

    ps- i did search the forums but not much info on the 4 stroke kits.

    Attached Files:

  2. Hi,

    Hard to tell from the pics where the choke lever is but if you take off the air cleaner housing and air filter you should be able to see a metal plate that is attached to a lever that moves it up and down to open and close off the carb air intake...that lever would be your choke lever if the carb is so equipped.

    Can's tell you about the screw but if you can start your engine and let it run until warm you could screw it in slowly and if the engine rpms rise you may have found the idle speed screw...if it doesn't rise just return the screw to the starting position and wait for somebody that knows for sure to answer the question about the screw....well actually you can still experiment to see what it is....if the engine starts to have black smoke when the screw is turned that would indicate that it is a mixture screw (black smoke indicates a rich mixture)

  3. salfter

    salfter New Member

    If you scroll about halfway down this thread, you'll see a gray lever over the air-filter housing. That's the choke...left is open, right is closed.

    On the left side of the carb, based on the adjustments I've tried and what the previous poster said, is the idle-speed screw. Mine started 2 1/4 turns out. I've had some problems with bogging after running a while; adjustments of this screw appear to have not had the desired effect. I'm guessing the next thing to do will be to try digging into the carb to see if there's an idle-mixture adjustment somewhere. There's also the larger black plastic screw on top; that'll control how much the throttle is open at idle. If you adjust one of these screws, you'll probably need to adjust the other one as well.

    Another thing I'm considering is getting rid of the metal shield around the cylinder. I can't see that it'd do anything other than cause the engine to run hotter than it should.
  4. stowaway

    stowaway Guest

    fuel air

    The guy i bought the motor from got back to me and said it was the fuel/air mixture screw.

    I've got mine idoling great now. I just played with that screw plus the screw that holds the acelerator in just enough to idol perfectly..

    now i just need to fix the valve. its leaking fuel.
  5. 4stroke 50cc


    I hear ya on the dui. Thanks for raising those questions about your carb and choke. The fuel/air mix screw on my honda gxh50 only has a 1 o'clock to 5 o'clock adjustment and i have not found it to be especially useful, but I will try again. i have been using my motor for the last 2 months regularly and probably have 100 hours on it with the larger sprocket (as i recieved 2 sprokets with my kit as well). I like the Honda, it gets me to about 35 mph before topping out on my heavy cruiser.

    However, my motor developed a tick at about 50 hours that i belive is valve clearence adjustment. the tick is clearly related to valve or piston movement and is one of the signs that clearence needs to be adjusted (re: operatos manual). apparently, the valve clearence adjustment is part of the standard adjustment of a 4-stroke, as i found the specs for clearence adjustment in both the honda gxh50 operators maual and my honda xr250 service manual. I have ordered the gxh50 service manual (33$ from www.helminc.com) to assure that i fix this problem correctly.

    Which gearbox did you get. it looks like the new gearbox from grubee, the starfire, which is supposed to be quieter than the old one. do you know if you GB is a grubee, or another brand. Does it have a high pitch whine when you get up to higher rpm's or is it quiet.

    Im posting a new thread under tech / mech with pics of my motor before i tear it down this week, check it out.

  6. stowaway

    stowaway Guest


    the picture i posted is NOT my motor. i took it from another thread.

    My motor is the starfire grubee one. I havent really tested it although i think it is quiet noisy. But there is things u can do to quiet it down. i havent had time to even fiddle with it yet. ive been too busy getting the bike up and runing.

    i took it for a test ride and it didnt go very fast. but it could have been due to the wrong fuel/air mixture. ive fixed that now, but havent had a chance to give it another ride.

    ill be posting more info and pictures as soon as i finish.
  7. honda vs. huasheng


    As i have read, the huasheng is a chineese replication of the honda. i just went with the honda becuase i have had an XR250 and a VFR750 and trust their 4strokes. I drilled a hole in the top of my gearbox and tapped it with a stainless bolt so i could have an oil port. i use either a couple squirts of ATF fluid (tranny fluid) or gear oil. i actually prefer the gear oil...it sticks around longer and doesnt leak out the bottom of the Gearbox.

    I didnt break it in though. i put that thing on and went full out the first day...oh well. actually i met Lathan ( a member) on my first ride, and it happened to be his first ride on his 2stroke. needless to say i smoked him, er, i guess he smoked me:eek:

    That may be why i need to gap the valves now. i dont recommend it though. Believe it or not my owners manual sail 200+ hours for break in. in commuter hours that is like 4 months!! I will be interested in your performance experience with you motor, and i bet you can use my posts to work on you bike, as the huasheng is probably an almost exact replica.

    Catch ya later.
  8. Stoltzee

    Stoltzee Member

    The grey lever on top is the "Choke Lever." Clockwise is Open, and Counter CW is choke. There are 4 positions also. Open, 1/3, 2/3, and full choke.
    The Screw in the picture is the "Idle Adjustment Screw."

    I read a post where someone said "Screw out for Rich." I don't know but all the engines I've ever played with, it was in for rich.

    Screw it in until the engine starts running uneven; lumpy or jumping around. Then screw it out until it "start's" to run smooth. Slightly rich is OK also.

    Race cars are always ran rich for racing.
  9. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    The screw in the pic is the air mixture screw just like the poster said in 2007.

    The idle screw is the big black philips which pulls on the throttle cable.

    Turning the mixture screw in makes it leaner because the opening around
    the tapered needle becomes smaller.
    Turning the needle out makes the opening larger and there for richer

    Start with 2 to 2.5 turns out.
  10. Stoltzee

    Stoltzee Member

    Geezzzz! I didn't pay attention to the date's. I'm going to have to do that from now on, and I'm glad everyone doesn't get notified, especially since I Wrote " Idle Adjustment Screw", when I meant "Mixture.
    What I failed to realize is that it's a Fuel screw, and not an Air screw on my 4 stroke engine. Dang Dern!

    It's been sometime since I worked on anything. When I lost my license I dead quit touching any thing with an Internal Combustion Engine..

    My carb has a solid brass plug in the hole, and I have not had any dire reasons to dig it out yet, except of course my obsessive compulsion to adjust things.
    Last edited: Oct 11, 2012