Bull 200 engine is running lean

Martin1978 · 08-06-2020, 11:56 PM

Hi, everyone,
I'm new to the forum here, would like to say hello to everyone! It's nice that this forum exists, since info on our machines is sometimes a little scarce. Soo... I have a question for those of you that have a gy6 powered quad, more precisely a Bull 200: I just bought a Bull 200 and it all seems to be in good working order, however I have noticed that the machine sometimes likes to die while idling, especially when the engine is still warming up. Also it will backfire at times when letting off the throttle, from experience with my mini bikes, I remembered that this means she's probably running lean. Upon checking the plug, I saw that instead of a nice coffee brown, the plug was kinda greyish. So I'd imagine that this is an issue I need to address. I stopped riding after that. The stock carb from what I hear is a California epa carb and can not be adjusted, so my first question is: Is this true and if it can be adjusted what do I need to alter? I know main jet and fuel/air mix screw. I just don't know what sizes will be ballpark. I'm in southern Utah, where it gets real hot and my elevation is 5400 feet. If the stock unit is useless, what other carb do you all suggest? I'd like a nice slide carb as an upgrade. So I need to know the mm diameter, what main jet, etc. I don't want to spend a mountain of cash. I was looking at the nibbi brand carbs. I guess the most important thing is, which mm do I need for it to bolt right up to my machine? I know that was a lot, however any help would be greatly appreciated. Thank you in advance!

**JerryHawk250** · 08-07-2020, 07:35 AM

Welcome aboard! The carb can be adjusted. There is either a brass or aluminum plug covering he idle mixture screw. It can be drilled out to gain access to the idle mixture screw. It's located on the right side of the carb nearest the engine.

To access the jets you will need to slot the bowl screws with a dremel or hacksaw so a flat head can be used to remove the screws.

SevereTrauma · 08-07-2020, 09:08 AM

Welcome. I can't wait for it to not be 100+ so I can ride my Bull again.

Martin1978 · 08-07-2020, 03:11 PM

Thank you so much for the help! I guess I'll pull the carb off and have a look. The mixture screw only adjusts the lower rpm mixture right? Or does it affect everything right up to WOT? Reason why I ask is do I need a new main jet? If so where does one get jets for the stock carb?

**JerryHawk250** · 08-07-2020, 03:23 PM

Quote:

Originally Posted by Martin1978

Thank you so much for the help! I guess I'll pull the carb off and have a look. The mixture screw only adjusts the lower rpm mixture right? Or does it affect everything right up to WOT? Reason why I ask is do I need a new main jet? If so where does one get jets for the stock carb?

It only adjust the idle mixture. They are usually set pretty lean. The main jet controls the 3/4- WOT.

Martin1978 · 08-07-2020, 10:15 PM

Did as suggested, slotted, bowl screws, drilled the mix screw cover, adjusted screw 2 1/2 turns out, reamed the main jet to approx a #100 from #94 and guess what? Smooth starts/idle, no more backfires engine runs cooler, plug looks normal now and still has same power. I call that a win! Cost? $0. Thank you so much for the help it's really appreciated!

FLASHLIGHTBOY · 08-09-2020, 06:55 PM

I do not understand.... making the jet bigger and this gives more fuel... how it runs cooler... and the air screws.... do they only effect the air mixture at idle ... at highter rpm... the air screw does do nothing>??? please correct me if I am wrong... so more fuel ... lets it start easier... that is like if you raised the clip on the throttle body rod down... the the needle will come up to expose the hole in th e jet to let it suck in more fuel.... for start up... ok... will wait for the jury on this...

dugndeep · 08-29-2020, 10:40 AM

When I first got mine I had trouble with the idle after start-up,I think the electric choke wasn't right but now that it has got broken in,it works fine.I get a few backfires when I let off the throttle from wide open,I just assume that is normal for a CARB compliant vehicle now-a-days.

Fumblecopter · 08-29-2020, 10:49 PM

So has anyone bought a replacement carb for these? If so, which one?

Fumblecopter · 09-27-2020, 08:34 PM

So I bought a new carb on amazon...found here. https://www.amazon.com/dp/B01G3M42L6..._s5sCFbKCEXR0Y works great after I plugged up the empty hole on it with an m8 screw. Seems to run stronger now. Old carb got crud in it because the lousy fuel filter wasn't really filtering anything.

08-07-2020, 07:35 AM	#2
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,585	Welcome aboard! The carb can be adjusted. There is either a brass or aluminum plug covering he idle mixture screw. It can be drilled out to gain access to the idle mixture screw. It's located on the right side of the carb nearest the engine. To access the jets you will need to slot the bowl screws with a dremel or hacksaw so a flat head can be used to remove the screws. __________________ 2023 Lifan Lycan 250 Chopper 2023 Venom Evader 2022 Lifan KPX250 2020 Kawasaki Vulcan S (Sold) 2004 Honda ST 1300 2016 Black Hawk 250 (sold) Keihin PE30 carb,125 main,38 slow.Pod filter,ported & decked head 10:1 CR,Direct Ignition Coil,15/40Sprockets,NGK DPR8EIX-9,De-Cat,Dual Oil Cooler,Digital Cluster 2016 Cazador180 XL 2014 Coolster150 JerryHawk250.com My YouTube Channel
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08-09-2020, 06:55 PM	#7
FLASHLIGHTBOY Join Date: May 2009 Location: SASKATOON Posts: 1,161	jet I do not understand.... making the jet bigger and this gives more fuel... how it runs cooler... and the air screws.... do they only effect the air mixture at idle ... at highter rpm... the air screw does do nothing>??? please correct me if I am wrong... so more fuel ... lets it start easier... that is like if you raised the clip on the throttle body rod down... the the needle will come up to expose the hole in th e jet to let it suck in more fuel.... for start up... ok... will wait for the jury on this... __________________ DEALER FOR ZSTAR & GIO PRODUCTS, TAOTAO ABIBABA ATV ETC
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08-06-2020, 11:56 PM	#1
Martin1978 Join Date: Aug 2020 Location: St.George, Utah Posts: 3	Bull 200 engine is running lean Hi, everyone, I'm new to the forum here, would like to say hello to everyone! It's nice that this forum exists, since info on our machines is sometimes a little scarce. Soo... I have a question for those of you that have a gy6 powered quad, more precisely a Bull 200: I just bought a Bull 200 and it all seems to be in good working order, however I have noticed that the machine sometimes likes to die while idling, especially when the engine is still warming up. Also it will backfire at times when letting off the throttle, from experience with my mini bikes, I remembered that this means she's probably running lean. Upon checking the plug, I saw that instead of a nice coffee brown, the plug was kinda greyish. So I'd imagine that this is an issue I need to address. I stopped riding after that. The stock carb from what I hear is a California epa carb and can not be adjusted, so my first question is: Is this true and if it can be adjusted what do I need to alter? I know main jet and fuel/air mix screw. I just don't know what sizes will be ballpark. I'm in southern Utah, where it gets real hot and my elevation is 5400 feet. If the stock unit is useless, what other carb do you all suggest? I'd like a nice slide carb as an upgrade. So I need to know the mm diameter, what main jet, etc. I don't want to spend a mountain of cash. I was looking at the nibbi brand carbs. I guess the most important thing is, which mm do I need for it to bolt right up to my machine? I know that was a lot, however any help would be greatly appreciated. Thank you in advance!
	0

08-07-2020, 09:08 AM	#3
SevereTrauma Join Date: Oct 2019 Location: Tucson, AZ Posts: 85	Welcome. I can't wait for it to not be 100+ so I can ride my Bull again.
	0

08-07-2020, 03:11 PM	#4
Martin1978 Join Date: Aug 2020 Location: St.George, Utah Posts: 3	Thank you so much for the help! I guess I'll pull the carb off and have a look. The mixture screw only adjusts the lower rpm mixture right? Or does it affect everything right up to WOT? Reason why I ask is do I need a new main jet? If so where does one get jets for the stock carb?
	0

08-07-2020, 10:15 PM	#6
Martin1978 Join Date: Aug 2020 Location: St.George, Utah Posts: 3	Did as suggested, slotted, bowl screws, drilled the mix screw cover, adjusted screw 2 1/2 turns out, reamed the main jet to approx a #100 from #94 and guess what? Smooth starts/idle, no more backfires engine runs cooler, plug looks normal now and still has same power. I call that a win! Cost? $0. Thank you so much for the help it's really appreciated!
	4

08-29-2020, 10:40 AM	#8
dugndeep Join Date: Jul 2019 Location: Lancaster,Ky Posts: 442	When I first got mine I had trouble with the idle after start-up,I think the electric choke wasn't right but now that it has got broken in,it works fine.I get a few backfires when I let off the throttle from wide open,I just assume that is normal for a CARB compliant vehicle now-a-days.
	0

08-29-2020, 10:49 PM	#9
Fumblecopter Join Date: Apr 2018 Posts: 62	So has anyone bought a replacement carb for these? If so, which one?
	0

09-27-2020, 08:34 PM	#10
Fumblecopter Join Date: Apr 2018 Posts: 62	So I bought a new carb on amazon...found here. https://www.amazon.com/dp/B01G3M42L6..._s5sCFbKCEXR0Y works great after I plugged up the empty hole on it with an m8 screw. Seems to run stronger now. Old carb got crud in it because the lousy fuel filter wasn't really filtering anything.
	0