150cc GY6 hard starting

Nospark · 02-02-2022, 10:11 AM

Looking for suggestions on where I might look to solve a hard start problem.
Adjusted valves
New carb, fuel lines, vacuum lines.
Fresh non-ethanol fuel
New CDI box, coil, wire & plug
Fresh battery - turns over fine
What's the gap for a plug on a 150cc china scoot?

TominMO · 02-02-2022, 05:04 PM

A good general purpose gap would be .030" or more.

How is the cam timing? Always start with basics, no assumptions.

Does it start at all? How does it run after starting?

Nospark · 02-03-2022, 03:23 PM

Yes, it will eventually will start and run a bit on center stand but a lot of cranking. Runs poorly.
Damn. I'm my own worst enemy. I just pulled and checked the plug gap on brand new A#1 china plug that came with new coil. It's at .010" and appears as though the piston may have touched it. Can't be sure about the piston kiss but, I'm sure about the .010" gap. I'll just bet ya, if I guy were to put in a quality brand plug, correct for the application, gapped @ .030", some improvement in this hard start condition might be made. What is conventional wisdom on best plug in these 150cc GY6 scoots?
Oh, and I didn't even think about timing. I'll YouTube about that. I currently have no idea do you check and set it.

TominMO · 02-03-2022, 06:44 PM

Probably the plug is/was your problem. Seems like everyone is using the NGK plug. I'll see if I can find the exact model. My Lifan X-pect's plug originally had a very tight gap too.

Edit: NGK DR8EA. I'd go with .035"

krat · 02-04-2022, 12:42 AM

You did a lot to the bike and it sounds like you have little experience with this engine. All of it can affect the way the bike starts and runs.

Reading more carefully I see that you replaced the carb. What did you go to and did you check the jetting. The 150 GY6 seems to run best with a 105 main and 35 pilot.

Did you hook the stock air box properly?

Did you reattach the electric enrichment (choke) properly?

Your description of what it is doing sounds like a super lean condition such as you get when opening the air box without changing the jets in the carb.

Nospark · 02-04-2022, 11:59 AM

Krat, Thx. I put a new plug in, NGK C7HSA. It started right up and idles fine. I did check the gap on the plug this time. I used the factory setting of .024". I replaced the carb with a cross I found on Amazon. Set idle mix 1 & 7/8 out. For the price of a new carb, I didn't feel like messing with the one that was in there. I have not checked the jetting. Air box is stock. I did have small hole worn in air box hose but, used some silicone to patch.

Nospark · 02-04-2022, 01:17 PM

Here is the description of the carb I bought and installed. "150cc Carburetor for GY6 4 Stroke Engines 125cc 150cc ATV Go Karts Scooter Mopeds QMJ/QMI157 QMJ/QMI152 - Manifold Intake Fiameter 24mm PD24J Carb" It measures the same intake and exhaust as one that was on scoot. I'm at 600ft elevation here in Milwaukee.
I have a lot of experience with working on engines but, 1st time messing with China GYC scooter. The scoot was given to me. It was a basket case. Broken throttle cable was the obvious issue. Replaced throttle and grips. Then identified junk battery and bad battery terminals. Fixed terminals & installed new batt to find no spark at plug. Checked all wiring harnesses but couldn't find anything broken or shorting. Couldn't resolve no spark issue after swapping out all new ignition system components and electrically checking each new component to confirm it was working as designed. So.... I cut kill circuit wire at CDI, then got spark. Wired in a kill switch so I could kill ignition after start. Wouldn't start so figured fuel/air. Drained old fuel, added new fuel. No joy. Replaced pitcock, fuel filter and fuel lines as I wasn't smelling fuel at the carb. Still no pop. Pulled and tossed carb and replaced. Then it would hard start and idle poorly. Confirmed wrong plug and gap and replaced with NGK with proper gap. Starts right up, idles great. Shuts down with kill switch. Can't test ride in Milwaukee yet unless you want frost bite. Will change oil and gear oil next, flush brake fluid, adjust brakes. check tire pressure. Then land speed record run.

Nospark · 02-04-2022, 01:26 PM

Krat, Can you share a source for the jets that will fit the carb I bought? I can easily rejet it but again, it needs to be jetted fr my elevation.

Nospark · 02-04-2022, 01:51 PM

Krat, Can you share a source for the jets that will fit the carb I bought? I can easily rejet it but again, it needs to be jetted for my elevation.

65cabriolet · 02-04-2022, 03:34 PM

perhaps these are what you're looking for?

https://www.amazon.com/Glixal-125cc-...ps%2C86&sr=8-3

Nospark · 02-04-2022, 03:52 PM

Thx, for the link for the main jets. I ordered them. Still want to find source for pilot jets.

krat · 02-04-2022, 09:54 PM

If you are now starting and idling OK I would not mess with the pilot jet. all it does is sustain smooth idle.

Your needle takes over almost immediately after you start rolling on a GY6. It controls flow up to 1/2- 2/3 or so on the throttle and then the main jet kicks in.

You might want to shim the needle but that can be done with tiny stainless steel washers from any hardware store and save yourself the hassle of ordering and waiting for delivery.

Scoot49 is the best place to go for scooter carb education.

https://www.youtube.com/c/49ccscoot

Nospark · 02-07-2022, 11:37 AM

Krat, Thank you. Most helpful. I agree on the needle as next priority if the scoot doesn't respond to throttle well. I keep finding things that messed up that need correcting. I'm the forth owner. The other three should have left their tools in the box. I should have done this sooner, but tonight I'm going to check compression. Obviously I have enough for the engine to start and idle but, I'm curious to learn just how much life may have been beaten out of this grinder. I did change the engine oil last night. Looked surprisingly good. Replaced with synthetic 15W-30 cause that's what I had sitting around. Drained gear case and looked and smelled decent as well. I'm going to fill that with synthetic as well, 75W-90. I didn't have any. Gotta visit the Autozone for that later today.

02-02-2022, 05:04 PM	#2
TominMO Join Date: Sep 2021 Location: De Soto, MO Posts: 1,977	A good general purpose gap would be .030" or more. How is the cam timing? Always start with basics, no assumptions. Does it start at all? How does it run after starting? __________________ 2021 Lifan Xpect--sold 2022 Lifan KPX 1972 Honda CT90--The Carrot 1969 Honda CT90--The Tomahto Cheesy is the WDK (workplace drama king). Now retired. Nope, back in the saddle. Nope, finally retired. Climate: The Movie https://www.youtube.com/watch?v=A24fWmNA6lM How our government really works https://www.youtube.com/watch?v=QjadCd0VRBw Question all authority.....think for yourself
	0

02-03-2022, 06:44 PM	#4
TominMO Join Date: Sep 2021 Location: De Soto, MO Posts: 1,977	Probably the plug is/was your problem. Seems like everyone is using the NGK plug. I'll see if I can find the exact model. My Lifan X-pect's plug originally had a very tight gap too. Edit: NGK DR8EA. I'd go with .035" __________________ 2021 Lifan Xpect--sold 2022 Lifan KPX 1972 Honda CT90--The Carrot 1969 Honda CT90--The Tomahto Cheesy is the WDK (workplace drama king). Now retired. Nope, back in the saddle. Nope, finally retired. Climate: The Movie https://www.youtube.com/watch?v=A24fWmNA6lM How our government really works https://www.youtube.com/watch?v=QjadCd0VRBw Question all authority.....think for yourself
	0

02-04-2022, 12:42 AM	#5
krat Join Date: Nov 2019 Location: KY Posts: 277	You did a lot to the bike and it sounds like you have little experience with this engine. All of it can affect the way the bike starts and runs. Reading more carefully I see that you replaced the carb. What did you go to and did you check the jetting. The 150 GY6 seems to run best with a 105 main and 35 pilot. Did you hook the stock air box properly? Did you reattach the electric enrichment (choke) properly? Your description of what it is doing sounds like a super lean condition such as you get when opening the air box without changing the jets in the carb. __________________ %90 of the Chinese motorbikes ever made are still on the road. The other %10 made it back home.
	0

02-04-2022, 09:54 PM	#12
krat Join Date: Nov 2019 Location: KY Posts: 277	If you are now starting and idling OK I would not mess with the pilot jet. all it does is sustain smooth idle. Your needle takes over almost immediately after you start rolling on a GY6. It controls flow up to 1/2- 2/3 or so on the throttle and then the main jet kicks in. You might want to shim the needle but that can be done with tiny stainless steel washers from any hardware store and save yourself the hassle of ordering and waiting for delivery. Scoot49 is the best place to go for scooter carb education. https://www.youtube.com/c/49ccscoot __________________ %90 of the Chinese motorbikes ever made are still on the road. The other %10 made it back home.
	0

02-02-2022, 10:11 AM	#1
Nospark Join Date: Jan 2022 Location: Milwaukee, WI Posts: 167	150cc GY6 hard starting Looking for suggestions on where I might look to solve a hard start problem. Adjusted valves New carb, fuel lines, vacuum lines. Fresh non-ethanol fuel New CDI box, coil, wire & plug Fresh battery - turns over fine What's the gap for a plug on a 150cc china scoot?
	0

02-03-2022, 03:23 PM	#3
Nospark Join Date: Jan 2022 Location: Milwaukee, WI Posts: 167	Yes, it will eventually will start and run a bit on center stand but a lot of cranking. Runs poorly. Damn. I'm my own worst enemy. I just pulled and checked the plug gap on brand new A#1 china plug that came with new coil. It's at .010" and appears as though the piston may have touched it. Can't be sure about the piston kiss but, I'm sure about the .010" gap. I'll just bet ya, if I guy were to put in a quality brand plug, correct for the application, gapped @ .030", some improvement in this hard start condition might be made. What is conventional wisdom on best plug in these 150cc GY6 scoots? Oh, and I didn't even think about timing. I'll YouTube about that. I currently have no idea do you check and set it.
	0

02-04-2022, 11:59 AM	#6
Nospark Join Date: Jan 2022 Location: Milwaukee, WI Posts: 167	Krat, Thx. I put a new plug in, NGK C7HSA. It started right up and idles fine. I did check the gap on the plug this time. I used the factory setting of .024". I replaced the carb with a cross I found on Amazon. Set idle mix 1 & 7/8 out. For the price of a new carb, I didn't feel like messing with the one that was in there. I have not checked the jetting. Air box is stock. I did have small hole worn in air box hose but, used some silicone to patch.
	1

02-04-2022, 01:17 PM	#7
Nospark Join Date: Jan 2022 Location: Milwaukee, WI Posts: 167	Here is the description of the carb I bought and installed. "150cc Carburetor for GY6 4 Stroke Engines 125cc 150cc ATV Go Karts Scooter Mopeds QMJ/QMI157 QMJ/QMI152 - Manifold Intake Fiameter 24mm PD24J Carb" It measures the same intake and exhaust as one that was on scoot. I'm at 600ft elevation here in Milwaukee. I have a lot of experience with working on engines but, 1st time messing with China GYC scooter. The scoot was given to me. It was a basket case. Broken throttle cable was the obvious issue. Replaced throttle and grips. Then identified junk battery and bad battery terminals. Fixed terminals & installed new batt to find no spark at plug. Checked all wiring harnesses but couldn't find anything broken or shorting. Couldn't resolve no spark issue after swapping out all new ignition system components and electrically checking each new component to confirm it was working as designed. So.... I cut kill circuit wire at CDI, then got spark. Wired in a kill switch so I could kill ignition after start. Wouldn't start so figured fuel/air. Drained old fuel, added new fuel. No joy. Replaced pitcock, fuel filter and fuel lines as I wasn't smelling fuel at the carb. Still no pop. Pulled and tossed carb and replaced. Then it would hard start and idle poorly. Confirmed wrong plug and gap and replaced with NGK with proper gap. Starts right up, idles great. Shuts down with kill switch. Can't test ride in Milwaukee yet unless you want frost bite. Will change oil and gear oil next, flush brake fluid, adjust brakes. check tire pressure. Then land speed record run.
	0

02-04-2022, 01:26 PM	#8
Nospark Join Date: Jan 2022 Location: Milwaukee, WI Posts: 167	Krat, Can you share a source for the jets that will fit the carb I bought? I can easily rejet it but again, it needs to be jetted fr my elevation.
	0

02-04-2022, 01:51 PM	#9
Nospark Join Date: Jan 2022 Location: Milwaukee, WI Posts: 167	Krat, Can you share a source for the jets that will fit the carb I bought? I can easily rejet it but again, it needs to be jetted for my elevation.
	0

02-04-2022, 03:34 PM	#10
65cabriolet Join Date: Feb 2018 Location: Brighton CO Posts: 54	perhaps these are what you're looking for? https://www.amazon.com/Glixal-125cc-...ps%2C86&sr=8-3
	0

02-04-2022, 03:52 PM	#11
Nospark Join Date: Jan 2022 Location: Milwaukee, WI Posts: 167	Thx, for the link for the main jets. I ordered them. Still want to find source for pilot jets.
	0

02-07-2022, 11:37 AM	#13
Nospark Join Date: Jan 2022 Location: Milwaukee, WI Posts: 167	Krat, Thank you. Most helpful. I agree on the needle as next priority if the scoot doesn't respond to throttle well. I keep finding things that messed up that need correcting. I'm the forth owner. The other three should have left their tools in the box. I should have done this sooner, but tonight I'm going to check compression. Obviously I have enough for the engine to start and idle but, I'm curious to learn just how much life may have been beaten out of this grinder. I did change the engine oil last night. Looked surprisingly good. Replaced with synthetic 15W-30 cause that's what I had sitting around. Drained gear case and looked and smelled decent as well. I'm going to fill that with synthetic as well, 75W-90. I didn't have any. Gotta visit the Autozone for that later today.
	0