The chain of my son razormx350 is runing backwards, how can I fix it?

I would first look under the seat and check for an obstruction. My wife's car had this issue a few years back and it turned out that one of my son's baseballs had gotten under her seat. It would still move forward, but would not go back. If that isn't your issue I would have the switch checked. If not the switch then look close at the wires. Wouldn't think it would be the motor, they either work or they don't.

when u replaced the battery sir

Infiniti/Nissan Seat fix - YouTube

? 3:31
www.youtube.com/watch?v=L1pTDadNdLw
May 25, 2012 - Uploaded by Nathan Melendez Fix the seat motor on a Infiniti Qx4 or a Nissan Pathfinder, and most other cars. ... Make seat make a clicking ...

I think your chain is worn to the point of needing to be replaced.
A chain that loose can break at high RPM and do a lot of damage to the saw and the person using it.

BR

Get a new one or a use one and repalce it your self

You will need to replace the power seat track transmission assembly. The reason is this, they do not service the parts, just the whole assembly, it is very expensive if available so I suggest you google used power seat transmissions and see if you can locate one.

The battery is located under the seat. Take your key and insert in the seat lock on the left side of the cycle. part #7. http://www.bikebandit.com/houseofmotorcycles/2004-honda-nrx1800-rune/o/m2423#sch309211 Lift of the seat and the battery is held in by a rubber strap and the two battery cable bolts. http://www.bikebandit.com/houseofmotorcycles/2004-honda-nrx1800-rune/o/m2423#sch310546

I think you have a short in the seat motor. Doublecheck circuit breaker for electric seats. It has a reset button on it. Perhaps it has tripped. If yes, need to find short in seat.

Unplug the joystick cable under the seat remove the seat if on a post lift handle on right side under seat and lift seat off post if not look for release levers behind front seat post and seat will rotate backwards to give you access to the batteriesdisconnect battery cables and install as on old batteries to new ones and reinstall Hope this helps

The wires will have pulled off the circuit board inside.

Remove screws (force a hex driver in there) and solder wire back on.

Train surgey (geddit) is very fiddly. Have a drink first! ;-)