This is my first 2 stroke in like 30 years.  When I first got my blaster, it was a fresh rebuild and ran great.  Now, it seems when I start it, let it warm up a little and take off, it don't want to build the rpms.  It is a lot colder now.  After a while it gets better but its kinda like a main jet being dirty where the low end is good but top end stutters.  Also, it wont idle now.  Should I pull off the carb and clean it or could the plug be getting fouled?  I have no idea what jets it has.  It has full FMF exhaust, .020 bore, full rebuild top and bottom, maybe 6 hours and was heat cycled and retorqued .  Timing is advanced 4 degrees.  I have the stock key to put the timing back to stock.  I want to ride on trails so should I put the timing back to stock?  Thanks guys.  Also, I think there may be too much oil in it.  where should it be on the site glass?  Thanks.