Which hotend does not clog and is good to use with a Bowden 1.75 mm setup?
To make the suggestion of Martin Carney a real answer and shift things away from comments:

Yes, moisture and dust can be a problem. Find elaborations on the moisture here:
Does filament have to be stored in an airtight environment.

Also, dust getting into the hot end won't make extrusion easier. (link with suitable information needed). There are filament cleaning 'devices' for print on thingiverse, have a look at things with the tag: filament cleaner.

There are some other things that are mostly discussed in relation to hot-end clogging, which are printing speed, retract setting and what I would call hot-end resistance. For all of those, read through this thread and refine your question according to what you tried and what the results were:
Repeatedly Clogged Printrbot Simple Extruder.