It appears to be one of the genuine Lifan 127's (54 x 55.5) with 138 on the cylinder ! It's got the Lifan quality control certificate with it . Just ask him (thru contact seller) to guarantee that it's a genuine Lifan and will come in a sealed and unopened box from the Lifan factory - then save the email plus his reply - then pay him with a credit card or paypal (if he takes it) - then hit him with "item not as described" and get a full refund if it turns out to be non genuine .
For some reason or other , some Lifans come with the logo cast on the side and some don't . DHZ's 140's don't have Lifan on the cases either - but they are delivered in a Genuine Lifan box and have the certificate with them . Some of the all black 140's on ebay have Lifan on the cases - it's a bit of a head scratching situation . Maybe a seller can shed some light on the subject ?
I have a Lifan 120 with 124 in raised casting on the cylinder and it has Lifan cast on both cases and was delivered in the Lifan box with the inspection certificate . I paid more for it (at the time) than our 140 . Who knows - maybe Lifan sells the engines a bit cheaper without the logo on the cases !
138's sold in the US have Lifan on the side and look the same as the 124's :
eBay Motors: LIFAN 138CC ENGINE MOTOR XR50 CRF50 XR CRF 50 Z50 125CC (item 270125180568 end time Jun-05-07 02:29:11 PDT)
Maybe they have a "special" ebay sellers order line with assembled engines that have blank cylinders sitting in boxes ready to go . Then when they get an order for a certain cc capacity engine , they quickly get an assembly line of old peasants with small hammers and centre punches to give them their cc capacity ????????????