Lifan 125cc oil info

[Markntony]

Hello everyone,

I bought a chinese pit bike to learn more about mechanic. Well I bought the right thing, cause When I started it, it was smoking like crazy, and liquid oil was dripping out of the exhaust port.

I changed the piston and piston rings. I also changed the gaskets on my way there, and finally, I ajusted valves and made sure they seat properly.

I don't think the cylinder is worn out, but I don't know what the ring gap is supposed to be.

Now, When I start it, there's way less smoke, but still a bit of liquid oil coming out from exhaust.

That leads me to 2 questions I would like to ask:

1- could it be a broken valve stem seal?
2- about those valve stem seal, I would like to know, how does this engine lubrication works, I don't get how oil can go from the engine Block to the head of the engine, where the cam and valves are.

thanks for your help

 

[andrewmac805]

Sorry can't help with your questions! But I have the 125cc lifan that has started to leak oil out of the exhaust too! Where did you get your rings and piston from?

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[Markntony]

I bought them from ebay!

I bought a first kit, and for some reason, I was not able to fit the piston in the cylinder and ended up binding the oil rings... I then ordered the exact same kit, but from another seller (it came with an orange keychain)... Can't Remember which seller it was though.. And this time I had no problem installing.

Now I would like to do some more tests, but Just as I installed the piston, the kick starter broke on me haha... Waiting for a New one.. Still from ebay.

 

[CookieMonster]

Hi,

In my opinion, it could be either, but I have not had the problem myself, and I’m not sure what the gap is meant to be.

Regarding question the second, the oil comes from the crank case and is pumped up one of the head studs and then at the head it is forced to the rear of the head (opposite to timing chain) where there is a plate with galleries that directs it inside the camshaft. The oil is then flung in the camshaft to lubricate the rocerks /cam and also flung around the head to cool it. The oil then returns down by the cam chain to the crank case.

With the exhaust valve being on the low side of the head you get oil pooling around the stem seal, if the seal is worn, then it could leak through. The seals should be available online and should not be too hard to replace, I’m sure there is a diy somewhere on his forum.


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[Markntony]

Thank you very much!

That was exactly the kind of explanation I was looking for

It should help me figuring out the problem.

 

[Markntony]

When I took the head and cylinder apart, I saw two "spacers" coming out from one of the studs. If I remember well, one was between the head and the cylinder, and the other one was between the cylinder and the crank case.

Are those two spacers there to allow oil to the head?

I'm almost sure I didn't replace them at the exact same place they were, cause I didn't find any information on where to place them.

Does anyone know, if I need to place them around one specific stud?

Thanks

 

[CookieMonster]

No worries, I think they go on a specific stud, I can’t remember which one, it’s been a while since I had the engine apart, it’s currently gathering dust in the garage.
I think their main purpose is as a dowel pin to properly locate the head to the cylinder, not sure about the oil flow I’d think it would be a bit restrictive for letting oil pass. Better to have a looser bore on the hole.


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