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How It Works! 150cc GY6 Automatic Choke
[76,264 views - 62 comments - Rating 4/5 ****- ]
We frequently receive questions about how the auto-choke and its operating needle work. 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.

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.

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.

To test your auto-choke:
1. Remove choke assembly from the choke holder on the side of the carb. The needle should be clearly visable.
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.

If you need an auto-choke or other related parts, we have them available here:

Auto/Electric Choke

Auto/Electric Choke Control Resistor

Electric Choke O-Ring Seal
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62 comments about this article:
Poster #1 [04/21/10]
Cant keep my Yerfdog running? Will start no problem. Can someone help me?
Poster #2 [05/20/10]
poster one iam having the same prob right now so iam hoping someone will answer you
Poster #3 [06/07/10]
I had the same problem untill I removed the carburetor and cleaned it thoroughly. No problems now.
Poster #4 [06/20/10]
I am having the opposite problem. Wo't start without choking off manualy or using starter fluid. Once it did start and was warm started and ran good for a while. Cleaned carb,jets everything three times. Replaced electric starter/choke still no good. Ordered new CDI am thinking I should have ordered resistor though now. Will see what happens. Any other suggestions?
Poster #5 [07/06/10]
I replaced the carb with a new one, carb is flooding out when engine is not running, do you have a display or diagram showing where all the lines hookup or is there something else i need to check
Poster #6 [08/18/10]
i had a similar problem for a while thought it was auto choke or dirty carb. cleaned the carb still didnt stay running. After going through some stuff just tightened the idler screw (it kind of unscrews itself from vibration i guess) once that was done started and ran like a dream.
Poster #7 [08/19/10]
to poster #5 The problem sounds like a very simple fix. All you need to do is check the setting on the float located in the carb bowl. If the float is set improperly or the float is stuck open it will cause this problem. All you need to do is check and make sure that the float is actually closing the gas inlet valve by moving the needle upward into the valve correctly thus stopping the gas flow into the carb bowl as intended. I will explain the procedure further if needed but this is 99.9% the cause of your flooding.
Poster #8 [09/13/10]
I have a Yerf go cart Model 4209. It will not start cold unless i use starting fluid, if I hold gas pedal to fast idle it will run okay-the minute i let go of gas pedal it stalls. it seems as a choke and internal carb problem-what do you recommend?
Poster #9 [09/23/10]
I have a yerf dog 150cc and the gas keeps running out of the top hose. Almost looks like it flooding itself and dumping fuel and won't idle keeps shuting off. Any suggestions on what to check?
Poster #10 [09/25/10]
simpe fix for all of you guy's need to check your auto control choke resistor 5w-50hm it may be bad and fluding it out or it will not start proper ..............your gas valve in the carb is open from this resistor being bad .
Poster #11 [09/25/10]
I have gas going in the engine oil on my 150cc dune buggy .......
Poster #12 [10/04/10]
i have a gy6 150 scooter it starts and idles for about 20 sec.then goes dead. and as it is runing it is smocking looks white or light blue if give it gas it starts to rev. up then goes dead.
Poster #13 [10/20/10]
I am having trouble with my yerf dog gx 150. it starts and idle fine but when you get in and start riding it will sputter and has no power i cleanes the carb and the main jets and still it run like crap. it doesnt have any power either.
Poster #14 [10/20/10] Rating 1/5 *----
can you go without the auto choke ? it cranks and idles find but when you give it gas it will start sputtering and has no power
Poster #15 [10/31/10]
got a yerf dog 150cc wont start,cleaned carb,it seems to be getting fire and it has compression.What do you think.
Poster #16 [11/06/10]
my terminator gocart runs great when its warmed up ,the problem is getting it to start and keep running when its cold. i have to hand choke it to start the first few times if you touch the gas pedal it dies
Poster #17 [11/10/10]
i have same problem as poster 13, 14. any ideas?
Poster #18 [11/10/10]
i have same problem as poster 13, 14. any ideas?
Poster #19 [11/11/10]
set the intake valves.
Poster #20 [12/05/10]
i have a hammerhead twister with a gy6 150cc engine and i can start it but as soon as i give it gas sometimes it will go and sometimes it will bogg and stall out
Poster #21 [01/27/11]
my 150cc starts and runs but you give it some gas it wants to bogg down
Poster #22 [02/21/11]
only runs for 5 minutes when cold and wont idle?gy6 150
Poster #23 [03/16/11]
I have a carter talons Gx150IIR. Had no spark. Replaced CDI. Have spark now but still would not start. Removed and thoroughly cleaned carb. I have gas making it into the bowl but it doesn't seem to be getting out. Will run with starter fluid but dies as soon as you stop giving it fluid. Checked and cleaned both needles. What next.
Poster #24 [04/18/11]
I have a 150cc that starts dood and idels good but whin i give it gas it stals.
i have cleaned the carb and jets what am i missing?

Poster #25 [04/25/11]
My auto choke is not working right and i found that when i start my engine i have power to my choke but only a very short time and ends with no power at all to the choke. My 12 volt light tester starts off with showing power to no power in the line of the yellow wire. Is this normal and if not what should i look for
Poster #26 [05/16/11]
I have a Metal Motorsport 150KT that's not running well. If I can get it started, it will eventually sputter, backfire and die. Sometimes, it runs fine, then it starts sputtering, cracking and backfiring if you run it full throttle it dies. If you try starting it right back up it won't start until you turn the ignition all the way off and then back on and then it will start. PLEASE HELP!!!!!!!!!!!
Poster #27 [06/18/11]
i have a gy6 150cc hammerhead and it runs good all summer long. when it is cold outside it wont start without manual choke whats wrong with it
Poster #28 [06/23/11]
i have a crossfire 150 and it was starting fine now it wont even try and start . is it in the wiring
Poster #29 [07/05/11]
i have a baja 150 reaction and starts up runs but when I try to give it gas it wants to die.what do I do I cleand through 2 times already!what do I do?
Poster #30 [07/07/11]
Make sure your air filter is clean of dirt, my kart used to do that all the time till I ran a high flow air filter, just make sure you keep it clean.
Poster #31 [07/07/11]
Make sure your air filter is clean of dirt, my kart used to do that all the time till I ran a high flow air filter, just make sure you keep it clean.
Poster #32 [08/07/11]
I have yerf dog 3206 and when I hook up the battery smoke comes out from the stator anybody know about this problom?
Poster #33 [08/31/11]
I also have a Yerf 150 cc Howlet and it keeps flooding out will not running. I cleaned the carb and still does it. Anyone tell me how to adjust the float?
Poster #34 [09/03/11]
when i took the choke out, the needle is fully out. is this normal?
Poster #35 [09/14/11]
having the same problem as poster #4 what do u thing what should i do
Poster #36 [10/12/11]
when i start my go cart and i press on the gas all it wants to do is die. if i keep the gas in the middle then it will start going but very slow. its suppost to go 50mph but it only goes 15mph. why is that
Poster #37 [10/12/11]
when i start my go cart and i press on the gas all it wants to do is die. if i keep the gas in the middle then it will start going but very slow. its suppost to go 50mph but it only goes 15mph. why is that
Poster #38 [11/08/11]
i got kinda the same problem it wont start i have to hold the throttle half open for it to start then it wnt stay running it dies rate out somethimes you have to spray starting fluid in the carb to even get it to fire im not sure what to do now
Poster #39 [12/11/11]
gy6 150 would start good but stall as soon as you give it gas. cleaned the carb etc, no change. I think the diaphrams in the carb were torn so I got a new one for like $35, its fixed. HTH
Poster #40 [12/27/11]
#6 above saved me a ton of time. Just tightened down the idler screw and my Yerf Dog 3206 now idles without dying and starts much easier. This took about 5 minutes to correct.
Poster #41 [01/25/12]
Under: To Test Your Auto Choke, Step 3. It says the Black wire is Negative. However, the pictured choke has yellow/green wires as does mine. Do I assume Green is the Negative wire?
Poster #42 [02/21/12]
Does anyone have the proper jet/screw settings for Yerf 3206? I picked up a cart that was sitting for about a year or so outside. Was going to ultrasonic clean carb. and wanted to know the correct factory settings. Thx.
Poster #43 [05/10/12]
Poster #44 [05/14/12]
Just bought a used Yerf dog for my son. Ran great on the test run etc, but once it was sitting, gas started to dribble out the intake side of carb. I'm thinking a stuck float...gave it a couple of good taps with a mallet, but no luck...anyhting else I should be looking for when I pull the carb?
Poster #45 [06/06/12]
i have a yerf dog 150 and its fairly new. it is extremely hard to start up i have replaced the spark plug the ignition coil the cdi i have cleaned the carb i have put the valves to .005 for both intake and exhaust it would start to run if i hold up the needle in the carb can anyone help?
Poster #46 [06/26/12]
I bought new carb for crossfire 150 beat my brains out trying to make it run and then i finnaly took jets out of old carb and put them in new carb come to find out new carb had to small of jets in it.
Poster #47 [07/13/12]
Yerf dog spiderbox, seems like it is not keeping spark, tries to start and then nothing, replaced coil and still same problem, cleaned carb and nothing.
Poster #48 [09/09/12]
guys please dont use starter fluid as it will ruin these engines
Poster #49 [10/03/12]
how does the rectifier work
Poster #50 [10/25/12]
Why wont my rover go uphill
Poster #51 [11/26/12]
I recently bought a Yerf Dog GY6 150cc buggy and am trying to get ir running. I replaced a blown coil and have fire and compression but I noticed that the choke has two wires coming out of the plug and only one is attached to anything. There are two female wire connectors that have no visible male counterparts. One comes from the choke plug and the other from the ground wires that are massed in a white wire nut. Any body have a clue where they should be connected?
Poster #52 [12/30/12]
I bought a new 150cc chinese dune buggy it turns over but cant git gas to the carb.
Poster #53 [03/31/13]
my go kart wont go no faster then walkin speed it sputters and backfires when i let off i cleaned the carb everything is good inside whats the problem with it its a gx 150cc yerfdog
Poster #54 [05/19/13]
i have a quantum carbide 150cc it wont start unless you spray carb clean in it. When it does run you have to hold it wide open or it wants to die.when you try to start without carb clean it fires sometimes, idles for a minute then dies or if you give it gas it will die. again you have to hold it wide open as soon as it starts. what is wrong with it
Poster #55 [05/26/13]
to num 54 seems like u have a vacum problem probably in intake hose. it tends to crack.
Poster #56 [06/04/13]
I have a tomberlin crossfire 150cc and it has started sputtering when revved out...any answeres to what could make it do that
Poster #57 [07/31/13]
post 51 your resister is missing
Poster #58 [08/04/13]
where can i find proper vacuum hose diagram for hammer head 150?
Poster #59 [09/01/13]
use carb and choke cleaner to start engines,it won't dry out your piston.
Poster #60 [10/21/13]
I have a Chinese ATV 150cc GY6 electronic choke. Won't start without starting fluid! After it warms up runs and starts fine! Allready replaced the choke, made no difference!
Poster #61 [11/26/13]
I have a carter talon 150 that will not idle. I have 2.1 vdc going to the enricher and am not sure that is enough to heat the wax up? can I up the voltage to speed the process up?
Poster #62 [12/08/13]
i have a hammerhead gts150 itll start and i can ride then when i stop ill hit the gass and itll just sit there and sound like its flooding itself i need help asap
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