": Hi the problem of my dirtbike won't start when I let it sit for the weekend.<br>: I don't think it is the sparkplung because I just put a new one in.Do you think it might be the piston because I haven't looked at it yet.Ithink it might be the airfilter<br>: <br>Of course you realize that this is a moped discussion board??? Anyway, ther is most likely not a problem with your piston or airfilter. If it's a ""hard to start"" problem, and you are getting a good spark, the most likely problem is a fuel/air related problem. This means a problem in the carburetor. If you give a more complete description of the problem, it will be easier for someone to help. Again, the chances are good that your no-start situation is related to the carb.<p>Steve."