Venting…

There’s a line on the left side of the engine (shown above) that is designed to collect overflow and fumes from the engine crankcase.    We’ve had a number of people ask what is in the line, and in particular, if it can contain gasoline.  What comes out of that line when draining it (there’s a plug to seal the line at the bottom) sure smells like gasoline sometimes.   We’ve asked Zongshen repeatedly if the line contains gasoline and the answer has always been that it does not.   What they communicated to us is that what is in the line is oil and not gasoline, and that there was no way for gasoline to get to that overflow line.   Until this morning, that is.    We asked the question again last night based on renewed interest in this question on a couple of the forums.    Here’s the answer we received this morning from a Zongshen engineering report dated 22 September 2015:

There are two possible reasons leading to “oil” or “gasoline” in the overflow line.

I.  If the seal of the balance shaft is broken or if the seal is not assembled well, there might be engine oil leakage.

II.  There might be some material in the overflow line, and it is normal and no problem. The material is a mixture of the gasoline and water (or just include a little engine oil).

When the rider cool starts the engine or when the engine is started in a low temperature, the some liquid gasoline may stick to the cylinder wall and goes into the crankcase when it enters into the combustion chamber. When the temperature of the engine turns higher, the liquid gasoline are volatilized and mixed with air and turns into a mixture air material. But when this mixture material comes into the overflow line, it is cooled, and it becomes a mixture liquid material of gasoline and water. It is a condensation phenomenon. Because of the special structure of NC250 and the overflow line, the condensed liquid material will not return the engine. During the road test of RX3 in 2014 we have found the liquid in the overflow line which is a mixture of gasoline and water. It is normal. It will not affect the engine or the model. The I. reason is with little possibility.

We offer our apologies for previously simply relaying what we were told (which subsequently proved to be inaccurate).