Over Rev,
Since I had put the atv back together and could no longer get at the bowl easily, I cheated and leaned out the mixture by lowering the needle. I also tried running with the air filter off. Both resulted in worse performance which would indicate running lean. That is when I pulled the plug and checked it to confirm that I was running too lean. Much too my suprise, the plug was black (way black) and covered in soot as opposed to the ash color I was expecting. This is when I noticed I was having trouble getting spark so getting spark became the focus of my trouble shooting.
A weak spark is just a guess based on what conditions I am seeing.
(intermitent spark when grounded on the cylinder head even with a clean plug, trouble starting, bad performance at full throtle that gets worse with more air, and a black sooty plug if I do manage to get it started). If I can rule out weak spark then that is one less variable and I can stop worrying about the electrical side.
I think I will take the carb off again, clean it, check the main jet as you recommened, lower the needle one slot and try to fire it. If it runs again, I will check the plug before I make any adjustments. I've tried so many settings now that I can't keep straight what order I did things in. How do you tell the difference between gas and oil fouling?
BTW - If these symptoms sound like something else or you think I am way off track by all means don't hesitate to say so. I am no mechanic and am working simply from this web site and a grade 9 small engines class that I took over 25 years ago
Thanks for your help
Chris.