lsm125, airbox+oil=bad

So my lsm125 has been dumping oil out of the air box. When it happens my oil reservoir doesn't decrease so I'm guessing its a combination of water and oil. The garage I bought the thing from claims because I'm going flat out (60-70mph) for a sustained amount of time, but my route to work is ten mile of dual carriage way so I haven't got much choice.

I'm an amateur when it comes to mechanics so I need a bit of help with this. I'm pretty sure there shouldn't be oil in the airbox ever and I'm not sure how it would be getting there. I'd guess there's excessive pressure forcing the oil/water up the tubes, but don't know how id check or remedy this... something else I'd noticed was that the big tube leading to the air box has been compressed, is this going to make any real difference to the bike?
And last, but not least, the oil hose leading to the top of the head (which comes from an oil pump?) is slightly to small so oil drips onto the head. This is a five minute fix but when I disconnect the hose will oil flow freely from the hole or is there likely a valve of some sort preventing this?

Ta for any help!

Well, foam air filters must be oiled. Who knows, maybe mechanics were too enthusiastic with oiling.

I would certainly try to "uncompress" that compressed hose, because it is not hard to understand that air flow is decreased thru such a pipe.

As I know, these our Chinese small displacement engines have no by-pass valves or something similar in lubrication system. There are few calibrated holes here and there in the oil lines and that's it.

I would be concerned about that dripping in the cylinder head. Oil pumps in a cold engine, with cold oil, should pump at least 3 bar, and when the system reaches working temperature, not less than 1 bar. And you can understand that with this pressure, oil should not just drip into the head, but to flow in a strong, stable stream. Because of the only-dripping you mentioned, I would check the condition of rocker arms and camshaft lobes, to see that they did not get this bluish color, which indicates overheating of the head due to deficiency
of oil.

Ta for the reply Zorge. I'll have to strip the thing down tomorrow and have a proper look around. I'll take a few photos if anything looks dodgy.
And I didn't mean it drips, more that a small amount is being let out (the hose is about 5mm too short)

Hold on. As you can see, my English is poor, so let's go again: is there dripping happens INSIDE the motor head, where the rockers and camshaft are?

And one more thing: is your bike's engine stock, or is it modded, because you mentioned oil hose which could be disconnected, and I have not seen external oil line on the photos of the LSM?

I've tried to add a photo but on my phone so it may not work.
The top of the head has a metal tube, on this tube is a rubber hose leading to what I presume is an oil pump (not sure if it is a pump though). The hose is slightly to short so some of the metal tube underneath is showing. A small amount of oil escapes from the hose and leaks over the head casing.

Attachment 12379

Regarding the issue of "oil in the airbox" ...

I don't know your particular engine, but I am going to guess that it probably has some form of Crankcase Ventilation (CCV). CCV was one of the first engineering attempts at emissions control. Toxic fumes (including oil vapor) inside your crankcase were routed up a tube, back into the the airbox, so that these noxious fumes would be "recycled" and hopefully burnt up through the combustion chamber. It was common for a small amount of oil to appear at the bottom of the air box.

If, however, it looks like it is an oil/water mixture in the air box, this could point to something with a little more concern. If it is water, on an air-cooled engine (i.e., there are no water passages in the cylinder head), that would suggest water is somehow getting inside your crankcase (not a good thing). It is probably not water, though - it is probably fuel that might appear like water. Fuel vapor can get inside your crankcase if your piston rings are worn, and/or if the engine is overheating and/or being run at WOT (wide open throttle).

Also, overfilling engine oil (putting too much in) will cause some of that excess oil to be pushed up through the CCV system, depositing itself in the airbox.

A small amount of oil in the airbox is not a concern. It is unlikely (actually, impossible) that oil in an airbox could somehow be coming through the carb, and then through your paper filter, ending up deposited in your airbox. If your bike has an oil-impregnated air filter (unlikely with a 125), then that could also be a possible explanation. I'd guess that a simple 125 would use paper air filters.

Good luck.

Lao Jia hou, ta for the reply. I've been busy past few days, but plan on having a good look inside the airbox tomorrow, so I'll have a proper look at what's going on and report my findings back. As for the presence of water: I only presumed it was water because I'd notice my oil reservoir emptying more if the amount of liquid coming out was all oil, which I'm not. It makes more sense that its petrol because of the consistency of the liquid when it dries out a bit. Should I not be worried about fuel coming through then if I have had the throttle fully open for a while?


I've contacted lexmoto via Facebook and they've basically said the same. They've advised I reduce my oil from nearly full (1 litre) as it is to about 800ml. I must say they responded incredibly quickly and have answered a couple more questions I had.

Oh man, on your photo is not oil line - as Lao Jia Hou said, it is some kind air recirculation system. The entire system can be removed from the engine, but it is better that not to complicate your life. Simplest cure for this "salivating" would be a good, strong clamp. Also check this rubber hose, to be sure that there is no cracks or some other damage, and, if possible, I would try to fit it through another path, in order to eliminate that "about 5mm too short".

if you had water in the crankcase mixed with oil, you could see that the oil looks like a milkshake. It's not uncommon and, as practice shows, not deadly for the engine - it is sufficient to ride bike and because of the hot engine and oil, water will evaporate. I guess that you bike is not parked under the gutter, but certainly you can not avoid water to condenses in the crankcase. In fact, you can, by moving away from "Misty Albion". :icon10:

In other hand, petrol in oil is net a good thing. It shows that there is something deeply wrong, but I doubt that you wouldn't noticed that something is wrong with the engine (hard to start it, unstable running, no power, bike doesn't reaches his top speed). But, in any case, I would apply an old recipe for longevity of the engine - do not exceed 3/4 throttle.

Speedyspeedyboy, one more thing: I've noticed that pretty often guys from the UK ask questions about the virtually basic maintenance and repairing of their motorcycles, whether it comes to Lexmoto, Pulse Adrenaline or any Chinese bike. Is in the UK any C-moto forum, where people can share their experiences and information?

Cheers Zorge. Explained a lot for me. Everything you said makes perfect sense! Except for moving away from wet old England!
I visit a couple other bike forums but the general response to Chinese bikes is "get something else". Not to mention people are very good at guessing about engines they've not seen. I'm not very good with engines simply because I have less than a years experience on bikes!
I do try to avoid full throttle but my route to work is 10 mile of dual carriage way, and keeping a lsm at 60+ in wind or on a slight hill means I have to have it pinned.

I've been using this forum because despite limited members everyone seems happy to help, and they all know what they're on about! (Not to mention how funny some of the chinglish can be)

Tell me few more things: how much you weight and does your everyday itinerary has road climbs or bumper-to-bumper city traffic , or those are flat country roads with long stretches? I ask you this, because if you have a version of the itinerary closer to the second description, you might be able to squeeze out maybe extra ten miles of maximum speed by juggling with different size sprockets.

I'm 11.5 stone (73kg). Skinny but I'm 6.5 foot.
I'm mainly on tight twisty country lanes, between 30-50mph. But I spend a lot of time on long, straight, 60 - 70mph, two lane roads. I dont spend much time bumper to bumper but its necessary sometimes.
I really would appreciate a bit more top speed, but not sure if it'd be worth the lack of acceleration. And the acceleration would be good, but I'd not want to ride it if it was any slower. I really don't know though.

It seems to me you're the one who.... how to say... sets riding pace, and not, as it is in urban areas, traffic itself sets the pace.

If you get a chance, try a couple teeth bigger front sprocket or a half dozen teeth smaller rear sprocket. It may work for you.