How it works: 150cc GY6 Automatic Choke

We frequently receive questions about how the auto-choke and its operating needle work.  It’s a convenience that gets a bad rap from those desiring the control of a manual choke.  To the auto choke’s credit, usually problems starting and running on a GY6 engine are related to dirty carburetor jets, but the auto choke system can be to blame sometimes as well.

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A case of identity confusion

As it turns out, the auto-choke isn’t a choke at all.  That is, it doesn’t choke airflow through the carburetor like you would find on a lawnmower or generator type of engine. Instead, it sends extra fuel through the carburetor. This is called an enrichment circuit.

It's not a choke after all!

It’s not a choke after all!

The Choke Regulator Resistor


The magic Choke Resistor.

The function of the choke resistor is to make sure that your choke doesn’t get hit with a deadly dose of over-voltage at high engine RPMs.  If this resister goes bad, the choke will likely become damaged shortly thereafter.

How it all works

This circuit is controlled by the charging system. When your engine is off, the choke (enrichment circuit) is actually “on” in it’s default resting state. When the engine is turned on and voltage is applied to the choke, the needle extends and eventually plugs the enrichment ports within the carburetor. This happens within a couple of minutes as the engine warms up.

Testing your Auto Choke

What we usually see with a bad auto-choke is that the engine will start up and run great cold, but as the engine warms up there will be problems driving, starting, and/or idling.

Test Procedure

  1. Remove choke assembly from the choke holder on the side of the carburetor. The needle should be clearly visible.
  2. Measure the overall length of the choke from end-to-end, including the very tip of the needle.
  3. Now connect the choke’s electrical leads to a 12v power source. Black is negative.
  4. Wait 5-10 minutes and re-measure. The needle should have extended.
  5. The overall length should be approximately 3mm more than before.

45 thoughts on “How it works: 150cc GY6 Automatic Choke

  1. Don Rankin

    How do I remove the choke on the 150. Looks like you just pull it off. I don’t see any fasteners. Thanks, Don

    • Buggy Depot

      There is a golden-colored clip holding the choke in place. You’ll need to remove the two Phillips-head screws holding the clip in place, then you’ll be able to pull the choke right out with minimal force.

  2. Batha Nyathi

    Hi, why would you need to take/pull/disconnect your choke, is it not on the scooter for a reason?

    so my scooter won’t start with just my start and front break, like I normally start it, had to kick start it, took it to my dealer, who said I needed to disconnect my choker. I don’t understand that, surely there must be a greater problem than just pulling or disconnecting something? oh I had just taken in my scooter for a service three days later I had this problem

  3. Brandon

    My buggy starts fine and runs fine at idle, but boggs down and will eventually die under any heavy throttle or load. I can do about 10 mph on flat concrete. I cleaned the carbuerator and it still does the same thing. I even unplugged the auto-choke and it still did the same thing. Any thoughts? I already ordered a new resistor so once that gets here I will see if it fixes it.

    • HobbyGuy

      I am having the exact same problem. Fires right up but when i throttle up it doesnt. im thinking it was getting too much air. hence me here reading this article about the choke thing. Let me know if the new resister fixed it. or if wiring the resister could be the issue. i just thought of it and havent tried re wiring it.

  4. mike

    I took mind off my scooter it seems to work better
    it just has a little problem warming up butt that1s okay
    and i`m getting better gas mileage !

  5. Brandon

    I installed the new resistor and it still does the same thing. While working on it today, I was installing some new front lights and a rear running light; the stock ones didn’t work when I got it. I realized I have a bigger electrical problem. When I hooked up the rear tail light, the light would light up really bright and within a few minutes it blew. This happened to three different bulbs. Anybody have any ideas?

    • Brandon

      I installed a new voltage regulator hoping that was the issue. Engine still does the same thing but haven’t tried any new lights to see if they blow.

    • Joshua Mckie

      How do you install the resistor? What wires go to resistor? Thanks

      • Travis @ Buggy Depot

        AC from stator (yellow wire) -> resister (either leg) -> choke (either leg) -> ground

  6. Woz

    I’ve got the same problem as Brandon, the GY6 150cc engine will idle run up to the higher revs then start running like it’s starving. I have cleaned the carby 4 times, replaced the secondary coil, CDI unit, flushed fuel lines, checked for damages hoses & wiring, change the spark plug & gapped it, removed & checked the operation of the choke, I’m lost on what to do next. I’m in need of help!! Xmas is coming & the kids want the buggy on the track!!

    • Bryan

      Woz – I have the identical situation as you – with Christmas only 7 days away now! :(.

    • Robert Kosaski

      Have you tried to clean the tank filter / inline tank tube. I was having similar trouble where I could see the fuel fill the inline filter, then as the engine rev’d it would drain the fuel and empty the filter. I have taken it out of the tank and cleaned it and blew it out with compressed air and seem to correct my issue. Thanks to BD for allowing all of us to help each other trouble shoot and buy the right parts.

      • Ned

        Sounds like yall need to clean carb. Drain the fuel too, if there was any old in there. Change the filters as well. Idling good and bogs down under throttle, means not enough fuel. I would try the fuel filter first and go from there. Also check your vacuum lines for the fuel pump. If they are cracked, might be keeping the pump from working optimally.

  7. jae

    Hello and how are you all I have a Helix 150cc -can the auto choke
    be by passed

  8. Jody Johnson

    I have the same problem, been broke for two years. Runs and stalls. Brand new card, plug, hoses, filter, petcok, gas cap. Thing is driving me nuts.

  9. Chris

    I have a 150cc crossfire and was having the same problem. It would start fine, idles normal, and drive off as it should… but under full throttle it would bog down and act like it was flooding.

    I replaced the CDI, Coil, Spark Plug, Carberatur, intake manifold, Air filter, and Fuel filter. After all of that the buggy still bogged down exactly the same as before.

    I finally took the entire air box assembly and filter & all hoses off including the vacuum lines and she now runs like a bat out of hell. Full power and not bogging down at all.

    As soon as I put the air box back on it bogs down again. The problem must me in the vacuum lines but I cant seem to figure it out.

    For the mean time it runs great without all that hooked up. Any suggestions would be great!

    • tinyox

      Hi was just wondering did you find out the problem as i think i may have the same problem

    • Mike

      I have the opposite issue. We live in a colder climate and I can never get the cart to start without a dose of ether. I have replaced the carb and choke, installed the higher performance CDI set, replaced the spark plug and use premium gasoline in the cart. I also have the UNI intact filter. Once the cart is running, it works great, good power, good top end speed and idels smooth. It is just very hard to start. Any suggestions?

      • jeremy

        I have same problem find a salution yet?

    • Justin Slusser

      Hey All…. I read all these comments and was having the same exact problem… Started and idled fine, but missed and bogged down under full throttle. I took the carb off and cleaned it… Main jets were gross with a greenish film…. Put it back together and still same problem. I tried the no air filter suggestion, and it worked….ran great! Problem is, that’s not a solution I am comfy with. I knew then I either had a severe air restriction, or an over fueling problem. No air restriction was found, BUT I did notice that on the float valve in the carb, the metal tab the the valve itself hooks to was bent in such a manner as to allow the float itself to “bottom out” in the carb, before completely seating the valve. I took a small screwdriver and actually bent the tab downward so as to seat the valve quicker. This changed the overall position of the float within the bowl, to allow less gas in the bowl. I put it back in, and reinstalled all the air components, and it runs fantastic! Actually had to limit the throttle screw for the kids now! Thank you all for the advice and suggestions, I hope this is helpful to someone!!

  10. Edward

    I have a 150cc Zircon and runs drives great but at night when you turn on headlights it always seems to drain the battery you never notice it till you get home wash it off and try to restart it its brand new battery because i changed last one because i thought it was the battery turned out not to be and suggestions on what to check would be great..

  11. frans

    I took my auto choke of and tested it. Working 100%. As soon as I put it back on the carb it doesn’t work. I did rings and so on but bike stuggles to start run the batery flat. Looks like its not getting feul to the piston. Sometimes it does and a lot and sometime nothing.

  12. tp

    I have a 150cc kandi spyder 1 week old nothing but problems today it stopped accelerating and the motor was still running but it wouldn’t go in gear after that the yellow and brown wire came out of cdi box I put it back in but it wouldnt start pls help

  13. louis

    i have a yerf-dog rover model 34800 – 2003. i change wiring harness, 8 poles stator, flywheel, flywheel key, pickup coil, cdi, ignition coil, voltage regulator, spark plug and no have spark. only when i turn the switch on i see one single spark. after turning engine with starter i not see no more spark. can someone help me?

    • ernesto

      ck your cdi box if is dc or ac, i got the sane problem one spark and i got the cdi

  14. Chris

    I have a Baja Dune 150. Having an issue with idle and rough start-up. I have to spray carb to get it cranked. She runs like a beast after that with no issues while the RPM’s are high. As soon as I come to a stop and let off throttle it stalls out. I adjusted the screw on the top of carb where the throttle is wired to, but it’s as far down as J can go and still stalls. I’ve backed it out and tried different settings to no avail. Any ideas? I’m thinking carb issues but wouldn’t that effect the way it runs while on the throttle? After I added the items below she runs like a monster! I had these stalling/idling issues so I added the following:
    1 xTHROTTLE CABLE (old one broke)
    1 x SPARK PLUG

    Any advice would be greatly appreciated!!

    • Nevada Scooter Authority

      Clean carb, pilot jet clogged causing hard starting.

  15. Shane

    I bought a non-running go kart to help me learn more about engines. Have bought a new spark plug, CDI, ignition coil, and magneto and a new carburetor. The gas tank is clean with fresh gas but when I try to start it the motor will spin but nothing else happens.. idk what else i can do to make it work..

    • Tony

      I recently bought non running Hammerhead 80cc buggy. Problem was no spark. Fitted new CDI unit, coil, spark plug, still no joy. My neighbour is pretty good with electrics and he worked out that a DC, not AC, CDI was needed. Problem solved, goes like a train.

  16. Stan

    O.k. Just bought a 150 cc yerf dune buggy. For my sons birthday, ran good when cold, when it warmed up it tended to bog and die .i cleaned the carb and now it goes like a bat but dies when it stops.idle speed goes up and down intermittently, now for the real issue, When my son was speeding around our yard, the battery fell off and tore the cables out of their connections, I re assembled the system except for an inline fuse , I think it goes to the positive side of the coil, but no matter where I hook it I have no power to start it , any ideas anyone?

    • Kevin

      Maybe a bit late but the ground cable goes to the frame or engine bolt, the positive goes to the right side of the solenoid

  17. sarge

    I have an FX150 talon. Carb is super clean and starts and idles but when you step on the throttle it immediately dies? It sat for about 1 year + took carb to shop and they said it was like new, put new needle valve in blew out all parts of the carb with cleaner and air. When I first tried to run the engine it worked and took the gas fine after I put it back on after cleaning it is acting up. When I first started working on it, the air filter was full of gas, now no problem there.

  18. Bill

    Hello..I have a Helix 150cc buggy.. unsure of year(within the last few years I believe)..and I believe it has the gy6 will start but only run for a few seconds then dies out..took the carb of and took apart and soaked in parts cleaner a couple of times,put back together…same problem….checked spark plug,vacuum lines,it’s getting spark so the cdi is good..the fuel petcock seems to be working properly and it’s getting fuel to the carb..adjusted the fuel/air and idle screw appropriately,and the choke seems to be working.. even with the air box off..nothing seems to make a difference..any and all help would be appreciated..

  19. dan

    Just bought a 150cc buggy for my kids, guy said it was a hammerhead, but motor says kinroad. Not really sure what I got. Was pretty cheap and ran good for the first day or so but now when they give it gas it boggs out and stalls. Any suggestions?

  20. Jason

    Took air box off n vacumm lines,ran great but had to put vacumm lines back on cause without vacuum lines the gas ran out in carburetor bowl. Have to figure out tomorrow what to do about air filter so dirt dont get in. I had same problem as brandon.

  21. Mark

    I have a carbide 150cc go kart. It fires up ok and idles ok. If you shake it, it stalls out. If you are giving it throttle it will not stall. Any thoughts?

  22. Kevin

    Sounds like the fuel bowl is at the lower limit try raising you floats up a half turn

  23. Alen

    I have a 2005 hammerhead 150 gt sport and the problem is when it’s cold it won’t stay running unless I hold my hand on the air tube. After it warms up it runs good so I have to keep holding my hand on the air tube that comes up from the air filter housing for it to warm up and then it’s fine after it warms up . Thank you for any help

  24. shawn

    My problem is I bought used which didn’t run at first and it doesn’t accelerate past six seven mile an hourI replace the spark plug CDI all the electronics and a new carburetor. however I haven’t change the air filter or really mess around with the airbox so I’m not sure what my problem is but it seems to run faster at barely Idle or as soon as you put a little bit of gas on the throttle doesn’t really do much outside that. I’ve adjusted the valves twice , and the exhaust is broke at the muffler. It has enough power to crawl up a hill but won’t gain speed under any circumstances. And I feel like the throttle almost does nothing. I’m gonna try the air filter thing and the valve float mod.

    • Buggy Depot

      Based on your description, the most likely causes of your power loss is the broken muffler, and potential vacuum leaks in the intake tract. Check your intake manifold for cracks or dry-rot.

  25. shawn

    The intake manifold is brand new and all vacuum lines. The air filter I have not changed. I’m gonna try with intake off then try that valve float thing to see if it’s seating properly. Still scratching my head on this one for now?

    • Buggy Depot

      Be sure not to actually ride it with the filter off; It may be obvious, so forgive me for saying. We hear frequently of guys riding with no filter because it “runs better”. Pretty quickly turns into email/comment asking why the machine tests with low compression.

      I recommend against tweaking settings on the carburetor, if anything simply clean it out using our guide and leave the float settings as they are.

      Exhaust leaks are a common source of power loss and headache. A faulty exhaust gasket will cause loss of power, hesitation, etc. So if your exhaust/muffler is outright broken, that’s certainly the most likely cause of your issue and the first thing that is recommended for repair or replacement.

  26. Mike

    My Baja dune 150 keeps popping the fuse short somewere any suggestions .
    Would a bad component cause this? Resistor, CDI, I am lost anyone have the elec. diagram?


  27. Eric

    Hi, I have a 150cc twister think gy6 motor. I bought a couple weeks ago. Runs ok and has lots of power. After warm up it acts like it wants to die and sometimes it does but I can always start it right back up by giving it a pump on the gas. Main issue I’m having is when given full throttle and ran at a higher speed and then let off gas it backfires. Usually one good pop or two. It’s just annoying. I have cleaned the carb made sure all connections are good checked fuel filter and lines made sure auto choke is good and resistor. I can get it to idle fine by adjusting carb and throttle. But like I said slam on the gas and let it go and I get that backfire… Any suggestions? Thx!

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