bemyself,
I think, too that you're overdoing the oil in your home brew. Back many, many years ago (mid 1960s) when I was a fledgling modeler living in Hong Kong, castor oil and methanol were readily available and reasonable in price, whereas commercial glow fuel was horrendously expensive and hard to come by. Is this the case in Thailand?
As I remember, my formula was 4 parts methanol to 1 part castor oil like yours. Yes, you will get a gooey sludge running pure castor oil and part of the problem could be the quality of the castor oil. (I remember that the castor we used to buy back then differed in color and viscosity from batch to batch). It couldn't hurt, though , to richen up the mix a bit, especially if you see metal bits.
Just thought I'd share a bit of my own experience. Good luck.

papermache