Should I refuse my advisor's request to write a research paper? My school policy for PhDs does not require any publications, but it's good to publish anyway. Recently my advisor asked me to write a journal paper, but I have more experiments to focus on.

Should I refuse him or just put my work on hold for a while? Personally I want to publish, but this time I am really not in position to write quality paper as I need focus on my work to finish my PhD on time.
I suspect that the time you invest in writing any papers now will be mostly paid back because it will make it much easier to write your dissertation.

I published several papers during my PhD research, and am currently writing my dissertation. My first step was to copy the introduction from each paper into my literature review chapter, and put the body of each paper into a separate chapter of my thesis. Of course, I have to write segues and reorganise the information a bit, but that gave me a big head start on the dissertation. Of course, you'll need to check that the copyright agreement you sign with the publisher allows you to include content from your paper in your PhD dissertation (most do), and also verify that your institution allows this as well.

Another tip: If you write a paper, hang onto any material that you cut out to meet space requirements. You may want to include that material in your thesis.