I bought my 750 shadow about a year and half ago and it ran fine until the shifter needed fixed, after I fixed the shifter I have not been able to get it to start. It turns over but does not fire. A friend of mine looked at it and poured gas straight into the crads and it back fired but did not start. I have replaced the plugs and dumped the old gas. Does any one have any suggestions as to how I can get my bike running again?