Lifan KPX Throttle Response / possible detonation

letsride · 10-27-2022, 02:40 PM

Well after riding my KPX some more, I wanted to report this. I haven't mentioned it before now as I was hoping the control module would "learn" so to speak. Simply put a CARB has better throttle response than this bike has. It has been that way since the day I started it. There is a noticeable lag in the twist of the throttle and the engine reacting to throttle input.

Another issue I suspect is going on is I heard what sounds like detonation at low speeds. And no, I was not lugging a gear too high for the speed I was traveling. Not sure if it truly is detonation (spark knock) or something is vibrating under the tank towards the top end of the motor. I'll know more when I have time to yank the plug to read it. Hopefully it isn't a lean condition as I have no idea how to richen the mix

.

Just an update to this here community, I'm not one of those people who champion anything they own as being the greatest thing since sliced bread. I will spit the good, the bad, and the ugly.

**JerryHawk250** · 10-27-2022, 03:24 PM

I have no issues with mine. You can richen up the idle mixture. There is what called the Idle gulp adjustment screw on the throttle body. Some of the Xpect guys had this same issue you describe and that fixed it. Here's a link to the instructions.
https://netcult.ch/elmue/HUD%20ECU%2...4%20Manual.pdf

TominMO · 10-28-2022, 08:22 AM

Quote:

Originally Posted by JerryHawk250

I have no issues with mine. You can richen up the idle mixture. There is what called the Idle gulp adjustment screw on the throttle body. Some of the Xpect guys had this same issue you describe and that fixed it. Here's a link to the instructions.
https://netcult.ch/elmue/HUD%20ECU%2...4%20Manual.pdf

On pages 29 and 30. Thanks Jerry!
Note that in the instructions on page 30 they call the screw a bolt.
PS, no issue with my KPX's idle either.

**JerryHawk250** · 10-28-2022, 08:51 AM

Quote:

Originally Posted by TominMO

On pages 29 and 30. Thanks Jerry!
Note that in the instructions on page 30 they call the screw a bolt.
PS, no issue with my KPX's idle either.

It starts on page 40.

letsride · 10-27-2022, 06:05 PM

Awesome! Thanks Jerry I will give that a try.

**JerryHawk250** · 10-28-2022, 08:38 AM

Quote:

Originally Posted by letsride

Awesome! Thanks Jerry I will give that a try.

Let us know if it helped.

letsride · 10-28-2022, 02:32 PM

Quote:

Originally Posted by JerryHawk250

Let us know if it helped.

I sure will, I'll tinker with it this weekend.

pathn · 10-29-2022, 11:23 AM

RE idle gulp adjusting screw:
Not finding it my kpx.

Mine is kinda jerky at low throttle too. I checked the plug and it is not a nice tan, it's white and too clean. Idles good. I haven't sprayed wd40 on the intake yet, but the bolts are tight and clamp to the throttle body is tight. No CEL.

Any ideas?

**JerryHawk250** · 10-31-2022, 10:37 AM

Quote:

Originally Posted by pathn

RE idle gulp adjusting screw:
Not finding it my kpx.

Mine is kinda jerky at low throttle too. I checked the plug and it is not a nice tan, it's white and too clean. Idles good. I haven't sprayed wd40 on the intake yet, but the bolts are tight and clamp to the throttle body is tight. No CEL.

Any ideas?

I never physically looked for it on my KPX yet. I'm wondering if this is something that has changed on the KPX or may have a cover over it. Now i need to take a closer look to se if it even exist anymore.

Did you happen to take pictures of the throttle body?

Hunnicutt · 10-28-2022, 08:14 AM

Would 93 octane help your KPX?

**JerryHawk250** · 10-28-2022, 08:43 AM

Quote:

Originally Posted by Hunnicutt

Would 93 octane help your KPX?

The KPX doesn't need 93 octane. It will run fine on 87 octane which is what the specifications call for. It probably wasn't tuned correctly at the factory and is running a little lean. At least we know how to correct it if it happens. When I did my valve adjustment i pulled my plug. Nice light tan color.

letsride · 03-20-2023, 10:46 AM

I have not dove into this issue with my KPX yet. I'm ashamed to admit the bike sits alot of the time, still doesn't have many miles on it at all. But I did start it up yesterday and let it run for a bit. The issue is still there, I need to figure it out. I plan to use the manual posted to see if this "gulp screw" exists on this model. I'll also see if I can make a video of what it's doing. I also need to pull the spark plug and check the color.

PATHN, Did you ever resolve the issue with your KPX?

TitusvilleRmiles · 02-25-2024, 05:09 PM

In response to this thread I have a 2023 KPX 250 with 25 miles on the clock and looking at this EFI manual shown on this thread my injection does not resemble this configuration. I am aware of the re-mapping of the cdi which I will take on at a different time to fix hesitation in throttle. I do not see any Idle gulp adjustment screw and have looked everywhere. The issue is: even though it idles ok it sounds almost like pinging/ engine ping/knock on immediate acceleration all gears. If it is too lean I cannot see where there is any adjustment screw. I am using 90 Rev octane from the get go. I thought it was a rattle and have tightened , zip tied everything under the sun.
I have checked all clamps and checked for air leaks.
email. is ok: rmilesmeritage@gmail.com

MotoJane · 04-30-2024, 11:59 AM

I picked up my KPX 250 a couple of weeks ago and I'm having the same issues as others with the ping/click during acceleration. I don't hear it at speed or idle just when I'm going through the gears. It can be loud so with a helmet on I have no issue hearing it. I checked the provided manual and this bike has no gulp screw. No adjustment screws at all that I can see on the 2023 KPX 250. Anyone find a solution to this issue? I only have like 50 miles on the bike. I contacted Venom the folks I got the bike from with zero response.

**JerryHawk250** · 04-30-2024, 01:55 PM

Quote:

Originally Posted by MotoJane

I picked up my KPX 250 a couple of weeks ago and I'm having the same issues as others with the ping/click during acceleration. I don't hear it at speed or idle just when I'm going through the gears. It can be loud so with a helmet on I have no issue hearing it. I checked the provided manual and this bike has no gulp screw. No adjustment screws at all that I can see on the 2023 KPX 250. Anyone find a solution to this issue? I only have like 50 miles on the bike. I contacted Venom the folks I got the bike from with zero response.

You will need to contact American Lifan. They will either send you a programmer to reflash the ECU or have you send in the ECU for them to reflash.

10-27-2022, 02:40 PM	#1
letsride Join Date: Oct 2013 Location: Leesville SC Posts: 835	Lifan KPX Throttle Response / possible detonation Well after riding my KPX some more, I wanted to report this. I haven't mentioned it before now as I was hoping the control module would "learn" so to speak. Simply put a CARB has better throttle response than this bike has. It has been that way since the day I started it. There is a noticeable lag in the twist of the throttle and the engine reacting to throttle input. Another issue I suspect is going on is I heard what sounds like detonation at low speeds. And no, I was not lugging a gear too high for the speed I was traveling. Not sure if it truly is detonation (spark knock) or something is vibrating under the tank towards the top end of the motor. I'll know more when I have time to yank the plug to read it. Hopefully it isn't a lean condition as I have no idea how to richen the mix . Just an update to this here community, I'm not one of those people who champion anything they own as being the greatest thing since sliced bread. I will spit the good, the bad, and the ugly. __________________ My Stable- 2022 Lifan KPX250 , 2023 Royal Enfield Himalayan, 1992 Honda GL1500 Goldwing, SSR 70 Auto, Kymco Mongoose 90, Honda Four Trax 300
	0

10-27-2022, 03:24 PM	#2
JerryHawk250 Moderator Join Date: Oct 2016 Location: Houma, La. Posts: 11,713	I have no issues with mine. You can richen up the idle mixture. There is what called the Idle gulp adjustment screw on the throttle body. Some of the Xpect guys had this same issue you describe and that fixed it. Here's a link to the instructions. https://netcult.ch/elmue/HUD%20ECU%2...4%20Manual.pdf __________________ 2024 Linhai 300 ATV 4x4 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
	2

10-27-2022, 06:05 PM	#5
letsride Join Date: Oct 2013 Location: Leesville SC Posts: 835	Awesome! Thanks Jerry I will give that a try. __________________ My Stable- 2022 Lifan KPX250 , 2023 Royal Enfield Himalayan, 1992 Honda GL1500 Goldwing, SSR 70 Auto, Kymco Mongoose 90, Honda Four Trax 300
	1

10-28-2022, 08:14 AM	#10
Hunnicutt Join Date: Apr 2021 Location: Central Florida Posts: 103	Would 93 octane help your KPX? __________________ ___________________________________ 2021 CSC TT250 - Silver (Mine) "Buzz" 2021 CSC TT250 - White (Wife's) "Seymour" 2021 CSC TT250 - White (Daughter's) "Gemini"
	0

03-20-2023, 10:46 AM	#12
letsride Join Date: Oct 2013 Location: Leesville SC Posts: 835	I have not dove into this issue with my KPX yet. I'm ashamed to admit the bike sits alot of the time, still doesn't have many miles on it at all. But I did start it up yesterday and let it run for a bit. The issue is still there, I need to figure it out. I plan to use the manual posted to see if this "gulp screw" exists on this model. I'll also see if I can make a video of what it's doing. I also need to pull the spark plug and check the color. PATHN, Did you ever resolve the issue with your KPX? __________________ My Stable- 2022 Lifan KPX250 , 2023 Royal Enfield Himalayan, 1992 Honda GL1500 Goldwing, SSR 70 Auto, Kymco Mongoose 90, Honda Four Trax 300
	0

10-29-2022, 11:23 AM	#8
pathn Join Date: Sep 2022 Location: pnw, southern baja Posts: 21	RE idle gulp adjusting screw: Not finding it my kpx. Mine is kinda jerky at low throttle too. I checked the plug and it is not a nice tan, it's white and too clean. Idles good. I haven't sprayed wd40 on the intake yet, but the bolts are tight and clamp to the throttle body is tight. No CEL. Any ideas?
	0

02-25-2024, 05:09 PM	#13
TitusvilleRmiles Join Date: Feb 2024 Posts: 12	detonation ?pinging In response to this thread I have a 2023 KPX 250 with 25 miles on the clock and looking at this EFI manual shown on this thread my injection does not resemble this configuration. I am aware of the re-mapping of the cdi which I will take on at a different time to fix hesitation in throttle. I do not see any Idle gulp adjustment screw and have looked everywhere. The issue is: even though it idles ok it sounds almost like pinging/ engine ping/knock on immediate acceleration all gears. If it is too lean I cannot see where there is any adjustment screw. I am using 90 Rev octane from the get go. I thought it was a rattle and have tightened , zip tied everything under the sun. I have checked all clamps and checked for air leaks. email. is ok: rmilesmeritage@gmail.com
	1

04-30-2024, 11:59 AM	#14
MotoJane Join Date: Apr 2020 Location: South West Posts: 10	Ping/Click KPX 250 2023 I picked up my KPX 250 a couple of weeks ago and I'm having the same issues as others with the ping/click during acceleration. I don't hear it at speed or idle just when I'm going through the gears. It can be loud so with a helmet on I have no issue hearing it. I checked the provided manual and this bike has no gulp screw. No adjustment screws at all that I can see on the 2023 KPX 250. Anyone find a solution to this issue? I only have like 50 miles on the bike. I contacted Venom the folks I got the bike from with zero response.
	0