Keeway k light 125 - low rpm popping and hesitation

SPORADIC · 10-24-2024, 06:55 PM

Hi all

Trying to get to the bottom of fixing this bike for my partner. Picked it up a while back and been doing little bits to it here and there.

The bike has done just over 3k miles on a 2019 reg.

The issue:

Giving the throttle a little blip or even a slow rev, it hesitates, pops, splutters etc then revs fine over 3k. if you rev it higher up the range then blip throttle, it will likley rev ok. It idles fine and only really cuts out after blipping or slow revving.

What iv fixed so far -

The 5v rail/supply to the map/intake sensor had low voltage/resistance. Traced this back to terminals needing tighening up as they corroded. Replaced the sensor while i was there. I deal in electronics so im not too bad with a multimeter. I have gone over the wiring diagram and checked i have the correct voltages/resistances etc to as many things i could test. Battery, rectifier etc all working well.

I have replaced the sparkplug for a fresh new ngk as i read the factory fitted are pants.

I have noticed a couple of things, i do feel like it smells a bit too strong of fuel. if i squeeze/restrict the intake manifold to restrict the airflow it clears up the throttle response right away and doesnt pop or lag.

There's a lot of induction noise, kinda like a bogging sound through the intake when revving.

Next step i think is valve clearance's

Just looking for a bit of direction. Thanks all

TominMO · 10-24-2024, 08:34 PM

Valve clearances should always be checked on these Chinese bikes, if only to eliminate that as an issue, so you do not have multiple issues to chase down.

My immediate guess is that your main jet is too lean. Especially if it is stock jetted for emissions. Squeezing the rubber manifold restricts air, so this artificially restores something like a proper mixture for too-lean fueling.

Thumper · 10-24-2024, 08:59 PM

Used and who knows how long parked or quality of fuel...

Before assuming it is jetted improperly...I would pull that carb and clean it. Check the float valve and use carb cleaner on the jets! And verify that fuel is flowing freely to the carb. Maybe that's all it needs.

And yes, check valve clearance. THEN, after you know you have a clean carb and valves adjusted, Test it.

SPORADIC · 10-25-2024, 02:40 AM

Thanks both for the replys! I should have stated properly that its an EFI bike. I have also tested the tps for the correct voltage/position and no flat spots. Forgot to say that in first post.

Truth be told, i added more fuel to the tank rather than draining. Thats a really good point maybe i should just drain it and run complete fresh.

Valves are on my list this weekend.

SPORADIC · 11-14-2024, 06:29 PM

Had a mega busy run latley so only managed to get some tool time in this week, the bike had to be put tothe bottom of the job list!

Fuel, plug etc all replaced, its still the same. I have stripped off the cam cover and had a look.

Im not sure exactly how to check with pushrod engines. Theres play in both rockers at true TDC. The gaps seem tight and hard to get the feeler gauges in without having to press the rocker back onto the ball/knuckle of the push rod if that makes sense??

ProDigit · 11-14-2024, 09:51 PM

Have you removed the cat, replaced the exhaust system, or done any intake or exhaust mods?

SPORADIC · 11-15-2024, 07:20 AM

Hi Prodigit

No, the bike is completly stock. In my opinion, for a bike
Of this engine size and the fact its running a standard airbox, it has a lot of boggy induction noise. Sometimes the popping is through the exhaust, and sometimes i have felt it through the airbox boot.

Going back to the valves, iv watched a few videos online. Some people "lift" the rocker up to put the feeler gauge in, some people sort of cut it into the gap.

I feel like the correct way to measure and adjust the gap is to make sure the rocker is tight against the pushrod. This would give the true gap.

10-24-2024, 06:55 PM	#1
SPORADIC Join Date: Oct 2024 Posts: 5	Keeway k light 125 - low rpm popping and hesitation Hi all Trying to get to the bottom of fixing this bike for my partner. Picked it up a while back and been doing little bits to it here and there. The bike has done just over 3k miles on a 2019 reg. The issue: Giving the throttle a little blip or even a slow rev, it hesitates, pops, splutters etc then revs fine over 3k. if you rev it higher up the range then blip throttle, it will likley rev ok. It idles fine and only really cuts out after blipping or slow revving. What iv fixed so far - The 5v rail/supply to the map/intake sensor had low voltage/resistance. Traced this back to terminals needing tighening up as they corroded. Replaced the sensor while i was there. I deal in electronics so im not too bad with a multimeter. I have gone over the wiring diagram and checked i have the correct voltages/resistances etc to as many things i could test. Battery, rectifier etc all working well. I have replaced the sparkplug for a fresh new ngk as i read the factory fitted are pants. I have noticed a couple of things, i do feel like it smells a bit too strong of fuel. if i squeeze/restrict the intake manifold to restrict the airflow it clears up the throttle response right away and doesnt pop or lag. There's a lot of induction noise, kinda like a bogging sound through the intake when revving. Next step i think is valve clearance's Just looking for a bit of direction. Thanks all
	0

10-24-2024, 08:34 PM	#2
TominMO Join Date: Sep 2021 Location: De Soto, MO Posts: 1,979	Valve clearances should always be checked on these Chinese bikes, if only to eliminate that as an issue, so you do not have multiple issues to chase down. My immediate guess is that your main jet is too lean. Especially if it is stock jetted for emissions. Squeezing the rubber manifold restricts air, so this artificially restores something like a proper mixture for too-lean fueling. __________________ 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
	1

10-24-2024, 08:59 PM	#3
Thumper Join Date: Feb 2021 Location: Kansas City Posts: 2,784	Used and who knows how long parked or quality of fuel... Before assuming it is jetted improperly...I would pull that carb and clean it. Check the float valve and use carb cleaner on the jets! And verify that fuel is flowing freely to the carb. Maybe that's all it needs. And yes, check valve clearance. THEN, after you know you have a clean carb and valves adjusted, Test it. __________________ No matter where you go, there you are
	2

10-25-2024, 02:40 AM	#4
SPORADIC Join Date: Oct 2024 Posts: 5	Thanks both for the replys! I should have stated properly that its an EFI bike. I have also tested the tps for the correct voltage/position and no flat spots. Forgot to say that in first post. Truth be told, i added more fuel to the tank rather than draining. Thats a really good point maybe i should just drain it and run complete fresh. Valves are on my list this weekend. Last edited by SPORADIC; 10-25-2024 at 04:42 AM.
	3

11-14-2024, 09:51 PM	#6
ProDigit Join Date: Aug 2013 Location: FL Posts: 376	Have you removed the cat, replaced the exhaust system, or done any intake or exhaust mods? __________________
	0

11-14-2024, 06:29 PM	#5
SPORADIC Join Date: Oct 2024 Posts: 5	Had a mega busy run latley so only managed to get some tool time in this week, the bike had to be put tothe bottom of the job list! Fuel, plug etc all replaced, its still the same. I have stripped off the cam cover and had a look. Im not sure exactly how to check with pushrod engines. Theres play in both rockers at true TDC. The gaps seem tight and hard to get the feeler gauges in without having to press the rocker back onto the ball/knuckle of the push rod if that makes sense??
	0

11-15-2024, 07:20 AM	#7
SPORADIC Join Date: Oct 2024 Posts: 5	Hi Prodigit No, the bike is completly stock. In my opinion, for a bike Of this engine size and the fact its running a standard airbox, it has a lot of boggy induction noise. Sometimes the popping is through the exhaust, and sometimes i have felt it through the airbox boot. Going back to the valves, iv watched a few videos online. Some people "lift" the rocker up to put the feeler gauge in, some people sort of cut it into the gap. I feel like the correct way to measure and adjust the gap is to make sure the rocker is tight against the pushrod. This would give the true gap.
	0