I think i have to replace the belt that is run by the underpullys, what is this belt called?? what are the signs that tell you that this belt needs to be changed and how much does it cost to get it replaced through mazda??

 

I'm pretty sure that the rx-7 store carry's the replacement belt. Also, K2RD.com carry's them.

 

It needs replacement when it looks old and you can see little cracks in the rubber ribs. Any auto parts store is likely to have a belt for you in stock, or be able to special order one if you need a weird size. If you have underdrive pulleys, the stock sized belt won't fit, so you may need to measure (use a string or tape measure) or try a few belts if you have lost the instructions, changed other pulleys, or the size has rubbed off your existing belt.

Belts are usually less than $20 and are not hard to replace. Just be sure you get the belt tension right, which you can do by moving the existing belt with your fingers to see how far it deflects and then set the tension for the new belt to be about the same.

-Max