are you by chance using gas with ethanol in it? if so, that gas will gum up in about 3 weeks and the pilor jets in the bikes crabs are sooooooooo tiny that they will get a small piece of gum or varnish in them real quick. I learned the hard way.....had my carbs ckeanes and re-synched twice this year before i FINALLY found out why from a mechanic. Now I only use 100% gas mixed with 1 oz. of Seafoam fuel additivee/stabilizer per gal. of gas. Mine runs awesome now.