My tw125 has done 23,000 miles and is used during May to October on a daily round trip of 16 miles with some rest days.

Occasionally, when I park it on the stand before trying to start it and open the fuel tap, there is a discharge of liquid from a drain tube behind the engine and in front of the rear forks. The liquid seems to be oily water. When this happens, the bike is impossible to start with the self-starter but can be bump started often with some reluctance.

I am guessing that the liquid comes from the emission separation box which receives crankcase vapours. Perhaps this liquid syphons off when the separation box is full. Perhaps also some liquid finds its way into the carburettor and this is hindering ignition.

Please can anyone advise me as to what is happening, why, and what to do about it? Thanks.

Totally different bike but I had an XJ600 Diversion that had similar symptoms with the leakage although mine wouldnt havent issues starting. Saying that though, does the breather pipe from the crankcase lead back into your Air Box? If it does have a look in the Air box, on the Divy I found that my air filter was sitting in a pool of this oily/water mix (Which I suppose could make it difficult to start..).

I just dismantled the box, gave it a good clean (including the inside of the pipe from the crankcase as it was all gunged up) and changed the filter, then after going for a good ride the performance difference was noticeable, as well as no more oily mess on the street when I park up.

Just a suggestion, hope this helps!