KPR 200 dies in the heat. Help!

[swolff]

Hey guys, I'm having an issue with my 2021 Lifan KPR 200. The bike has run strong since I bought it, but on the first 85°+ day this year I couldn't get the engine passed 3500 RPM without it just cutting out and dying. I took my car to work instead, and when I came back home at around 11:00 p.m, it worked fine. I had the same experience a couple days later when we had the same temperatures. Everything is fine up to a quarter throttle, after that it just shuts off like I hit the kill switch. I keep the bike outside under a cover, but there's really no shade so it gets quite hot. Is this something to do with the thermal protection system? If so, can I just replace the thermometer with a certain value resistor?

[TominMO]

What valve clearances are you running? If they are too tight (and they do get tighter with use), then you are getting no breathing, so it dies. An internal combustion motor is just an air pump, driven by gas explosions. Especially the exhaust valve tends to get hot because it does not have fresh cool gasoline vapor coming across it like the intake valve does to cool it off. The exhaust valve gets the hot burned gases. So typically the exhaust valve is set slightly looser for that reason. Lifan recommends .06mm for both. That's .002" BTW.

This may also have contributed to your earlier problem that you thought was the carb.

And of course the higher the ambient temp, the more likely you are to experience this.

[swolff]

I'm not sure what the clearances are. I haven't touched any of the internals on this bike. I will get my feeler gauges and report back. I am positive it's not a carb issue however; it's a fuel injected bike.

[TominMO]

Originally Posted by swolff

I'm not sure what the clearances are. I haven't touched any of the internals on this bike. I will get my feeler gauges and report back. I am positive it's not a carb issue however; it's a fuel injected bike.

Oh OK, I thought it was a carby. Yeah, then all the more likely it is valve clearance-related.

Edit: I went back to your previous posts and saw that the carb issue was with a Hawk.

[swolff]

Originally Posted by TominMO

What valve clearances are you running? If they are too tight (and they do get tighter with use), then you are getting no breathing, so it dies. Lifan recommends .006" for both...
...And of course the higher the ambient temp, the more likely you are to experience this.

I couldn't find my feeler gauge, so this has taken longer than it should have. I finally caved and bought a new one. TominMO, you are a saint. You were spot-on with your diagnosis.The valves were way too tight. After setting them to .05mm everything seems to be working correctly.

[KPM]

Originally Posted by TominMO

What valve clearances are you running? If they are too tight (and they do get tighter with use)

Can you please explain how or why ?

[Falkon45]

Are you getting any check engine lights before it cuts off? Is this problem immediate, or after the bike has been running for a while? It's it only happening in the heat? Have you checked you coolant levels?

[swolff]

Originally Posted by Falkon45

Are you getting any check engine lights before it cuts off? Is this problem immediate, or after the bike has been running for a while? It's it only happening in the heat? Have you checked you coolant levels?

No CEL. Correct, I only experience the issue when its hot outside. It happens immediately. I just checked the coolant, it's full.

[Falkon45]

Where does your ECU sit? Is it close to the fairing? If it is, is the sun shining directly on that side?

I'm trying to remember if these engines have air intake temp sensors or not. I have a feeling that could be an issue.

[swolff]

Originally Posted by Falkon45

Where does your ECU sit? Is it close to the fairing? If it is, is the sun shining directly on that side?

I'm trying to remember if these engines have air intake temp sensors or not. I have a feeling that could be an issue.

The ECU sits under the pillion seat and is directly against a black fairing that does get a fair amount of sun. It probably gets quite hot. Should I relocate it?

Edit: looking at the schematics for the bike, I do see an IAT sensor. I don't know where it's physically located, but it does seem that it's present.

[TominMO]

Before you start worrying about ECU location and IAT sensors, check your valves. Always do the simple and cheap fixes first. No one should have to relocate their ECU.

[J4Fun]

Is there a stuck thermostat possibly, just thinking out loud?

[ChopperCharles]

Also replace that stock spark plug with an NGK, preferably an iridium plug. The Chinese plugs are almost universally junk.

charles.

[ChopperCharles]

Because the valve is slamming against the seat over and over and over again, at double the engine rpm. So at 7000rpm your valves are opening and closing 14,000 times in one minute. Multiply that by thousands of miles. Bits of valve wear off, bits of valve seat wear off. The wear means the valve now sits higher in the head, which reduces the clearance between follower and cam.

Valves CAN go the other way, and loosen up with time. That is usually due to poor metallurgy in either the camshaft or the rocker/follower. Or poor oiling. Or both. The cam is wearing away faster than the valves can recede into the head. That was a big problem with 1980s Hondas, but it's largely solved now.

Charles.

[KPM]

Thanks for the explanation. I knew part 2, but part 1 is new to me.