VM26 jetting

Standaman · 12-30-2024, 05:43 PM

I know this conversation has been exhausted. But, I need help figuring out if I’m lean or rich. It’s a 04 GY-A 200, VM26, 165 main, 22.5, needle clip is in the middle, and 1 1/2 out on the air/fuel screw that’s( pre fuel bowl) just installed the “Genuine Mukuni” and trying to get it dialed in. I’ve gone from 120, 150, 165, 20 & 22.5. That’s all the jets I have at the moment. It has a uni filter and a aftermarket muffler. I live in VA , and today it was around 60 degrees. It’s not support stay this warm, after I warm it riding around the neighborhood, when I return I feel the engine is hot and sounds like it’s pinging a bit. But from the plug, it seems rich. When I hit the throttle from idle it Boggs, if I ease into it-it runs decent.

Standaman · 12-30-2024, 06:05 PM

https://www.icloud.com/attachment/?u...OV&sz=66616278

slithica · 01-05-2025, 11:59 AM

What jets are you running? It sounds like your idle jet is too lean and the main is too rich. Could be the valves too though, are they adjusted properly?

Standaman · 01-06-2025, 08:05 AM

I’m running 22.5 pilot and 165 main currently. Engine was just recently rebuilt with new piston and rings etc.. along with new stator and coil. Doesn’t help that in Va on the day of testing it’s 65 degrees now it’s in the 20’s and snowing just a week later. I purchased a genuine Mukuni last season and just got the time to install. My knockofff Mukuni had the fuel screw on the bottom and my genuine has the air screw pre fuel bowl closest to the air filter. As of yesterday once warmed up, in order to not hear the intermittent putt putt putt putt soumd and a bogg when I blip the throttle the air screw was a little more than 3 turns out which I believe is making it lean and I should decrease the pilot from 22.5 to a 20 I’m assuming. The putt, puttering sound is what I’ve never heard before and it’s driving me insane. I’ve spent the time dialing in the olde carb and know the routine. Then I thought what if it’s the coil & stator sense I had to buy two different ones from Aliexpress. It’s not like I can put a year make and model number. I can only go buy what 200cc, Chinese, Zhongshen, etc. And some product description still says some parts, size could vary from the product picture.

slithica · 01-06-2025, 10:12 AM

At 22.5 and 165 jets it sounds like they are indeed too lean at idle and too rich at throttle.

My engine is bigger than yours and uses a 145. I'm using the same carb too.

Standaman · 01-07-2025, 10:13 AM

Now that Im going down this rabbit whole, I'm starting to think it might be the new stator & pickup coil. My research has confirmed I installed a GY6 stator. Although it measured the same as my old one with slight differences. The attached pick up coil did not fit, so I ended buying one that was very close and wired it to the stator. It will start & go without any hesitation and plenty of power. As previous stated its the sound of a slight misfire at idle. the only way I can explain it - is it'll go (dadadada putt dadadada putt) haha , which will almost go away when I adjust the air screw. But, Ive gone from a 17, 20, 22.5, & 27 pilot. the 20 & 22.5 gave the best results but still has the crazy misfire. But not at full throttle... I did start a new Thread asking if anyone knows where I can purchase the CB style stator, it won't hurt installing the correct one, If I can find it..Ive also searched other threads but none of the links provided work. I do have a friend from China & has the taobao app and can order, but he says it's a process. So, I guess my question is ...can the GY6 Stator with & unknown pickup coil cause the interment spark/misfires & still run?

ProDigit · 01-07-2025, 09:57 PM

I'd start with a 35 pilot and a 120 main.
I hope you're putting that vm26 on a 150cc, because it's gonna be too big for a 125cc engine.

slithica · 01-08-2025, 10:11 AM

His first post says 200, so I hope that's what it is.

As for the pickup coil, if it's not the correct one... yeah it will cause issues.

I've honestly never used the wrong one so I can't say exactly what would happen if you used one that was slightly off spec wise.

You can measure the resistance between the new and old one to see if it's much different and lookup the spec possibly.

Most of these chinese bikes don't idle perfectly, hard to say if it's a bad misfire or not. Especially since it's just a single cylinder.

Mine runs great and all, but it's idle isn't perfect. Neither is the idle on any of my vehicles though. If you listen closely it's basically never perfect, even on newer vehicles.

So it's more about how off is it.

Standaman · 01-08-2025, 01:20 PM

Okay, yea I can give it a try, and Yes, its a ZS200 GY-A

ProDigit · 01-08-2025, 11:09 PM

For a 200, you're better off with a 28 or 30mm carburetor, though a 26 should give you rock solid idle with the right jets, but limits you in top speed.

Notjoemechanic · 01-16-2025, 03:28 PM

Start with an inline spark tester so you can see if you are loosing spark when it misfires. They are like 6 bucks on ebay. A bad cdi or other ignition components can sometimes cause intermittent missfires at specific rpms and make you think it is carb related. After you get the ignition sorted make absolutely sure you have no intake or exhaust leaks. Both will give you intermittent trouble when jetting and adjusting. Make sure you're float level is right and your float needle is properly seating. Make sure your choke or fuel enrichener is not sticking. It sounds to me you are way too lean at idle and way too rich on your main jet. Start with 1-1/2 turns on fuel screw and middle position on the needle just like you had it. Get your jets right first then mess with the fine tuning. I should run decent with just proper jetting first.

12-30-2024, 05:43 PM	#1
Standaman Join Date: Feb 2017 Location: Yorktown Va Posts: 20	VM26 jetting I know this conversation has been exhausted. But, I need help figuring out if I’m lean or rich. It’s a 04 GY-A 200, VM26, 165 main, 22.5, needle clip is in the middle, and 1 1/2 out on the air/fuel screw that’s( pre fuel bowl) just installed the “Genuine Mukuni” and trying to get it dialed in. I’ve gone from 120, 150, 165, 20 & 22.5. That’s all the jets I have at the moment. It has a uni filter and a aftermarket muffler. I live in VA , and today it was around 60 degrees. It’s not support stay this warm, after I warm it riding around the neighborhood, when I return I feel the engine is hot and sounds like it’s pinging a bit. But from the plug, it seems rich. When I hit the throttle from idle it Boggs, if I ease into it-it runs decent. Attached Thumbnails
	0

01-07-2025, 10:13 AM	#6
Standaman Join Date: Feb 2017 Location: Yorktown Va Posts: 20	Now that Im going down this rabbit whole, I'm starting to think it might be the new stator & pickup coil. My research has confirmed I installed a GY6 stator. Although it measured the same as my old one with slight differences. The attached pick up coil did not fit, so I ended buying one that was very close and wired it to the stator. It will start & go without any hesitation and plenty of power. As previous stated its the sound of a slight misfire at idle. the only way I can explain it - is it'll go (dadadada putt dadadada putt) haha , which will almost go away when I adjust the air screw. But, Ive gone from a 17, 20, 22.5, & 27 pilot. the 20 & 22.5 gave the best results but still has the crazy misfire. But not at full throttle... I did start a new Thread asking if anyone knows where I can purchase the CB style stator, it won't hurt installing the correct one, If I can find it..Ive also searched other threads but none of the links provided work. I do have a friend from China & has the taobao app and can order, but he says it's a process. So, I guess my question is ...can the GY6 Stator with & unknown pickup coil cause the interment spark/misfires & still run? Attached Thumbnails
	0

01-07-2025, 09:57 PM	#7
ProDigit Join Date: Aug 2013 Location: FL Posts: 402	I'd start with a 35 pilot and a 120 main. I hope you're putting that vm26 on a 150cc, because it's gonna be too big for a 125cc engine. __________________
	0

01-08-2025, 11:09 PM	#10
ProDigit Join Date: Aug 2013 Location: FL Posts: 402	For a 200, you're better off with a 28 or 30mm carburetor, though a 26 should give you rock solid idle with the right jets, but limits you in top speed. __________________
	0

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12-30-2024, 06:05 PM	#2
Standaman Join Date: Feb 2017 Location: Yorktown Va Posts: 20	https://www.icloud.com/attachment/?u...OV&sz=66616278
	0

01-05-2025, 11:59 AM	#3
slithica Join Date: Jan 2021 Posts: 67	What jets are you running? It sounds like your idle jet is too lean and the main is too rich. Could be the valves too though, are they adjusted properly?
	0

01-06-2025, 08:05 AM	#4
Standaman Join Date: Feb 2017 Location: Yorktown Va Posts: 20	I’m running 22.5 pilot and 165 main currently. Engine was just recently rebuilt with new piston and rings etc.. along with new stator and coil. Doesn’t help that in Va on the day of testing it’s 65 degrees now it’s in the 20’s and snowing just a week later. I purchased a genuine Mukuni last season and just got the time to install. My knockofff Mukuni had the fuel screw on the bottom and my genuine has the air screw pre fuel bowl closest to the air filter. As of yesterday once warmed up, in order to not hear the intermittent putt putt putt putt soumd and a bogg when I blip the throttle the air screw was a little more than 3 turns out which I believe is making it lean and I should decrease the pilot from 22.5 to a 20 I’m assuming. The putt, puttering sound is what I’ve never heard before and it’s driving me insane. I’ve spent the time dialing in the olde carb and know the routine. Then I thought what if it’s the coil & stator sense I had to buy two different ones from Aliexpress. It’s not like I can put a year make and model number. I can only go buy what 200cc, Chinese, Zhongshen, etc. And some product description still says some parts, size could vary from the product picture.
	0

01-06-2025, 10:12 AM	#5
slithica Join Date: Jan 2021 Posts: 67	At 22.5 and 165 jets it sounds like they are indeed too lean at idle and too rich at throttle. My engine is bigger than yours and uses a 145. I'm using the same carb too.
	0

01-08-2025, 10:11 AM	#8
slithica Join Date: Jan 2021 Posts: 67	His first post says 200, so I hope that's what it is. As for the pickup coil, if it's not the correct one... yeah it will cause issues. I've honestly never used the wrong one so I can't say exactly what would happen if you used one that was slightly off spec wise. You can measure the resistance between the new and old one to see if it's much different and lookup the spec possibly. Most of these chinese bikes don't idle perfectly, hard to say if it's a bad misfire or not. Especially since it's just a single cylinder. Mine runs great and all, but it's idle isn't perfect. Neither is the idle on any of my vehicles though. If you listen closely it's basically never perfect, even on newer vehicles. So it's more about how off is it.
	1

01-08-2025, 01:20 PM	#9
Standaman Join Date: Feb 2017 Location: Yorktown Va Posts: 20	Okay, yea I can give it a try, and Yes, its a ZS200 GY-A
	0

01-16-2025, 03:28 PM	#11
Notjoemechanic Join Date: Mar 2024 Location: Dothan, Al Posts: 30	Start with an inline spark tester so you can see if you are loosing spark when it misfires. They are like 6 bucks on ebay. A bad cdi or other ignition components can sometimes cause intermittent missfires at specific rpms and make you think it is carb related. After you get the ignition sorted make absolutely sure you have no intake or exhaust leaks. Both will give you intermittent trouble when jetting and adjusting. Make sure you're float level is right and your float needle is properly seating. Make sure your choke or fuel enrichener is not sticking. It sounds to me you are way too lean at idle and way too rich on your main jet. Start with 1-1/2 turns on fuel screw and middle position on the needle just like you had it. Get your jets right first then mess with the fine tuning. I should run decent with just proper jetting first.
	2