For something in the 26 to 35cc size have a look at the following and decide on what works for you price wise and which suits your application the best. The DLE is the powerhouse of the bunch. The MLD 35 looks good as a prototype, we'll see how it does once it is released.
Zenoah G26
DLE 30
Syssa SAP 180
JC 28
MLD 28 and soon to be released MLD 35