This might sound like a too good to be true infomercial buts its not.
I see a lot of this issue especially in the spring when people bring their bikes in for a tuneup after riding for a year or two, or even just from riding through the winter. The chain gets worn out.
There is a special chain wear checking tool that can show how worn a chain is. Ideally a chain should be replaced before its 75% worn. The reason for this is, the front chain rings and rear cogs wear along with the chain. If you wait until the chain is 100% worn or more, a new chain may not mesh well with the teeth on your chain rings and cogs, and could slip right out of the valley’s between the teeth, especially under load.
If your chain is over 100% worn there are likely only two options to remedy the situation. Leave the chain on and ride it until your drive system (chain, front chain rings and rear cogs) is completely worn out and then replace everything, or replace everything immediately.
Depending on the quality of the parts you want to have installed, the cost for type of job could start around $120 with parts and labour.
The life of the drive system can be lengthened considerably by checking the wear on the chain and changing it regularly. The frequency that it needs to be changed will vary depending on how much the bike is ridden, the weather and surface conditions its ridden in, and how often the chain is lubed and cleaned.
Generally, changing a chain once or even twice a year is considerably less expensive and inconvenient than being hit by a big bill for changing out your entire drivetrain when you least expect it.