I have 98 blaster and when I replaced the exhaust with the fatty pipe and fmf silencer I had to rejet my carb to get it to run, I had the same simptoms you are having, BUT why did the exhaust fall off? Because of damage, rust, heat? if it had an exhaust leak before it broke off it may have been tuned to compensate for the leak, if you sealed the leak now then you might be too lean or too rich, I adjusted my secondary or idle jet and I kick started no problem, give me alittle more info and I might be able to step you in the right direction.....