Lifan KPX Throttle Response / possible detonation

[Ratbagger]

Originally Posted by JerryHawk250

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.

[Thumper]

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.

Sounds like classic lean mixture. Good luck. Some folks do OK with it, but others have excessive lean issues.

My "primitive" carbed bikes can't adjust automatically for elevation/temperature. Nothing over 500 feet in evelation within 500 miles of here, but I will be moving. So I will rejet accordingly. You can do that with a carburetor.

[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

[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]

Originally Posted by 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