Lifan KPX Throttle Response / possible detonation

[letsride]

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 :hmm:.

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. :lmao:

[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%20Hacker/Lifan%20EFI%209%20Euro%204%20Manual.pdf

[letsride]

Awesome! Thanks Jerry I will give that a try.

[Hunnicutt]

Would 93 octane help your KPX?

[TominMO]

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%20Hacker/Lifan%20EFI%209%20Euro%204%20Manual.pdfOn 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]

Awesome! Thanks Jerry I will give that a try.

Let us know if it helped.

[JerryHawk250]

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.

[JerryHawk250]

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]

Let us know if it helped.

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

[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?

[JerryHawk250]

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. :hmm: Did you happen to take pictures of the throttle body?

[pathn]

I didn't until just now. The photos pretty much show what you can see from the right side. I did pull the bracket off that holds the throttle cable, and removed the wheel the cable attaches to. The left side has some sensors that I did not remove, but they don't look like there's room to have an adjustment screw under them.

I was riding it yesterday without a helmet and ear plugs (I'm in Mexico riding around a small town) and could hear the tinkle of spark ping. It's not a knock, and it's for sure not detonation (very destructive). The kpx is the first vehicle I've had with efi on an air cooled engine, so it could be normal. Still don't like the plug color.

My V6 ford van has spark ping when you start to load the engine (starting up a hill). Efi in cars with knock sensors advance the ignition until there is a knock, keeping the ignition as advanced as it can be. Seems to work with liquid cooled engines for a few hundred thousand miles...

Right side
https://journaldelpacifico.com/tbody_right_side.jpg

Left side

https://journaldelpacifico.com/tbody_left_side.jpg

[letsride]

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]

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]

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]

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.

[Ratbagger]

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.


I just contacted them and they told me to send my ECU to Venom Motorsports.

[MotoJane]

Well bummer on sending in the ECU. I just purchased this biking knowing about ECU issues with the bike. When speaking with the sales guy at Venom I asked if they would put the latest ECU into the bike and was assured it would be included. I need to call them, this isn't adding up. The throttle will give some slight hesitation and I know that points to the ECU or adjust the throttle. I've checked the throttle and it's fine, no major slack or kink. Well, heck.

[Megadan]

Well bummer on sending in the ECU. I just purchased this biking knowing about ECU issues with the bike. When speaking with the sales guy at Venom I asked if they would put the latest ECU into the bike and was assured it would be included. I need to call them, this isn't adding up. The throttle will give some slight hesitation and I know that points to the ECU or adjust the throttle. I've checked the throttle and it's fine, no major slack or kink. Well, heck.

Venom bought up a bunch of stock due to EPA regulations causing many of Lifans bikes to not be legal for the immediate future until they can pass certain regulations. You likely got shipped a bike from that pool of vehicles with an older ECU and Venom was simply not aware of it because they knew all of the bikes they were shipped had the upgraded ECU, and yours simply didn't.

[MotoJane]

Well after many, many attempts to have someone anyone over at Venom contact me it's a bust. My KPX 250 is a lemon and the company just isn't getting back to me on this issue. I called all last week, called this week and they keep telling me "someone" will contact you and they don't. At high idle the bike sounds like there is sand in the motor and when I drive it the bike knock/pings as you get down the road. I'm afraid it will leave me on the side of the road so I don't go far from home. I haven't even got the bike past 45 mph. I wouldn't in fear of my life. I have changed the old and put all the proper oil in the engine. I did find some flakes but the oil wasn't that bad. I think this thing is going to seize up while riding. I did ask them about the ECU and the customer care woman on the phone told me the bike was too new and it has the latest ECU flash. I guess I'm going to sell this junk online as scrap. I'm out over $3,000 buck.

[J4Fun]

If was my bike I would empty the fuel out and get fresh from somewhere else and see if that helps. I know it can’t be bad fuel, but it seems like it. My thoughts…

[MotoJane]

I've tried new fuel with no change. That was one of my first thinking. I will keep posting here "if" Venom ever comes back with any response or help diagnosing this issue, so far nothing.

[JerryHawk250]

Did you check to see if you have an exhaust leak where the header meets the head? You will get a similar noise with an exhaust leak.

[Megadan]

If you are not having luck getting in contact with Venom then call back American Lifan and inform them of your issue and see if they can offer an alternative. Sometimes you have to play the game a bit to get what you need. Just try to keep your cool, don't let your emotions run away with you and just approach it like a math problem that needs to be solved.

As for metal flecks in the oil, if the engine has less than a thousand miles on it, that will be normal. Seeing as yours has just 50 ish miles on it, expect a lot more. Part of the normal break-in process. Without being able to hear the engine for myself I can't give much diagnosis, but even if the thing is going to fail, Lifan has a 2 year warranty on those bikes if I remember correctly. Use it. Don't sell it just because you are emotional.

[buzz]

good luck

[PeanutRG]

Well after many, many attempts to have someone anyone over at Venom contact me it's a bust. My KPX 250 is a lemon and the company just isn't getting back to me on this issue. I called all last week, called this week and they keep telling me "someone" will contact you and they don't. At high idle the bike sounds like there is sand in the motor and when I drive it the bike knock/pings as you get down the road. I'm afraid it will leave me on the side of the road so I don't go far from home. I haven't even got the bike past 45 mph. I wouldn't in fear of my life. I have changed the old and put all the proper oil in the engine. I did find some flakes but the oil wasn't that bad. I think this thing is going to seize up while riding. I did ask them about the ECU and the customer care woman on the phone told me the bike was too new and it has the latest ECU flash. I guess I'm going to sell this junk online as scrap. I'm out over $3,000 buck.

You don't have a lemon and it's not scrap. You should upload a video of the noise so we can atleast hear it. The engine will quiet down as you break it in. Everything you've said is normal within spec.. I have 600 miles on my kpx and iv been running 90 ethonal free gas. Every once in awhile I also get a slight ping. Ecu has been sent in already.... it's normal. These are small thumper engines. They're going to sound like a well oiled sowing machine.

[JerryHawk250]

MotoJane, Another possibility is that the Valves may need adjusting. Even though it is a new bike, As many of us know on the forum. Most of these bikes come from the factory with valve gaps set to tight or even too loose.

[MotoJane]

I worked with my neighbor on doing a valve adjustment. He's a retired ASC mechanic. Wow, things went from bad to worse if that's possible. Something is wrong with this engine. The valves were tight but after doing the valve adjustment this thing click and clanks down the road. I wouldn't trust driving the bike more than 2 miles from my home. I'm at a loss. These bikes really don't have much in the way of adjustments. These noises in the engine are not normal, I've been riding bikes for over 30 years.

[JerryHawk250]

I worked with my neighbor on doing a valve adjustment. He's a retired ASC mechanic. Wow, things went from bad to worse if that's possible. Something is wrong with this engine. The valves were tight but after doing the valve adjustment this thing click and clanks down the road. I wouldn't trust driving the bike more than 2 miles from my home. I'm at a loss. These bikes really don't have much in the way of adjustments. These noises in the engine are not normal, I've been riding bikes for over 30 years.
Do you have any video so we can hear? That would really help in diagnosing the problem.

[J4Fun]

I worked with my neighbor on doing a valve adjustment. He's a retired ASC mechanic. Wow, things went from bad to worse if that's possible. Something is wrong with this engine. The valves were tight but after doing the valve adjustment this thing click and clanks down the road. I wouldn't trust driving the bike more than 2 miles from my home. I'm at a loss. These bikes really don't have much in the way of adjustments. These noises in the engine are not normal, I've been riding bikes for over 30 years.

With respect here, after adjusting the valves and it went from bad to worse, that’s pointing to the valves. We’re assuming that the engine was on the compression stroke when the valves were adjusted? Easy to to get things wrong here. Plenty of info. on how to adjust them here. Thinking out loud…

[MotoJane]

Do you have any video so we can hear? That would really help in diagnosing the problem.

:clap: Venom is in the building! They've called me! As for the sound, I've sent them a clip of it and they told me to stop riding the bike. They are working with the manufacture and we are on the road for a warranty issue. In the interest of the warranty and not wanting to hurt Lifan I'm not going to upload the video. I understand things happen, it's normally a one off, but this is the world not a video game.

[MotoJane]

With respect here, after adjusting the valves and it went from bad to worse, that’s pointing to the valves. We’re assuming that the engine was on the compression stroke when the valves were adjusted? Easy to to get things wrong here. Plenty of info. on how to adjust them here. Thinking out loud…

As I said I did have a real mechanic helping me with the adjustment. I agree something in the valves on this bike is seriously wrong and it isn't an adjustment. Maybe they aren't seating correctly or they are bent from the factory. I'm not sure but the way the sound of this engine something is seriously wrong.

[TitusvilleRmiles]

In regards to the noises and engine issues we emailed about here is what I got. After putting 200 miles on this bike I have accepted the minor noises that the engine makes and I am ok with it because of this quiet riding bike that has no muffler noise and you can only hear the engine, and that is ok with me. There is no detonation and I can only attribute the noises to engine vibration. As far a adjusting valves if you read the service manual you will easily find Top Dead Center easily by viewing the flywheel location and timing sprocket. I did this just to check the chain tension and it ended up ok. I want to add that I changed the oil at 50 miles on the odometer with the recommended oil and filter and yes the metal flakes were obvious. Riding with the this stock rear sprocket it is somewhat of a dog and in 2nd and 3rd gear cruising the local streets at 25 mph the transmission sounds whiney and tolerances may be the issue, but who cares , I don't. As far as the throttle response the re-flashing worked to some extent but, not great. I felt if I gave it a go at the TPS it might help and by ordering a test harness off Ebay ( see pic ) I was able to check and adjust the TPS value from .650 - .850 and it really isn't doing much. The service manual TPS value for idle is about .600 and I have tried several values and still not perfected. I am interested in swapping out this carb and then call it quits. I am ok with this bike and this is a lot of bike for the money but, here is the fact Jack. If you have ever rode a Honda, or Suzuki like I have you will not like the quality or power range of this bike. It is cheap, the parts are cheap, and the price is cheap. You get what you pay for and I again am impressed that someone can build a 250 for this price and make a profit. I will ride it most likely for another year and hopefully trade it in for a real bike.

[TitusvilleRmiles]

In regards to the noises and engine issues we emailed about here is what I got. After putting 200 miles on this bike I have accepted the minor noises that the engine makes and I am ok with it because of this quiet riding bike that has no muffler noise and you can only hear the engine, and that is ok with me. There is no detonation and I can only attribute the noises to engine vibration. As far a adjusting valves if you read the service manual you will easily find Top Dead Center easily by viewing the flywheel location and timing sprocket. I did this just to check the chain tension and it ended up ok. I want to add that I changed the oil at 50 miles on the odometer with the recommended oil and filter and yes the metal flakes were obvious. Riding with the this stock rear sprocket it is somewhat of a dog and in 2nd and 3rd gear cruising the local streets at 25 mph the transmission sounds whiney and tolerances may be the issue, but who cares , I don't. As far as the throttle response the re-flashing worked to some extent but, not great. I felt if I gave it a go at the TPS it might help and by ordering a test harness off Ebay ( see pic ) I was able to check and adjust the TPS value from .650 - .850 and it really isn't doing much. The service manual TPS value for idle is about .600 and I have tried several values and still not perfected. I am interested in swapping out this carb and then call it quits. I am ok with this bike and this is a lot of bike for the money but, here is the fact Jack. If you have ever rode a Honda, or Suzuki like I have you will not like the quality or power range of this bike. It is cheap, the parts are cheap, and the price is cheap. You get what you pay for and I again am impressed that someone can build a 250 for this price and make a profit. I will ride it most likely for another year and hopefully trade it in for a real bike.
The TPS harness on Ebay fit was for a Huskqvarna

[MotoJane]

I had a bad one and man what a mess that can be. After working with Venom I took my back back to Cali and they fixed it up. Yes, I said that right. I don't live that far so I was able to take the bike back for a total engine replacement. They checked the engine and yes it had something wrong. In the end the company stood by their product and fixed the bike. I'm riding my KPX now and it is a wonder machine.


:clap: Venom is in the building! They've called me! As for the sound, I've sent them a clip of it and they told me to stop riding the bike. They are working with the manufacture and we are on the road for a warranty issue. In the interest of the warranty and not wanting to hurt Lifan I'm not going to upload the video. I understand things happen, it's normally a one off, but this is the world not a video game.