Lifan KPX Throttle Response / possible detonation

[MotoJane]

Originally Posted by JerryHawk250

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

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]

Originally Posted by J4Fun

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]

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

[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.

Originally Posted by MotoJane

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.