I've done this on my Sportrak and all the Fourtrak's I've seen seem to have the same dash. I must say it's a fairly horrible job for what should be such a simple task.

First you must remove the plastic beneath the steering column or remove the glove box depending on which side you need to replace. Then the metal struts need to come out to free the edge of the dash from the centre console. There is a bolt located near the door hinge which will allow some movement in the section of the dash housing the speaker. You'll probably need an extension to reach it. There are three bolts across the top of the dash, one behind the three central gauges and one on each side about six inches from the corner of the windscreen. I would recommend removing the central one and the one on the required side.

You should now be able to push the dash housing the speaker out enough to access it with your head in the footwell. Two screws hold the metal plat that the speaker is attached to. One is easy to remove and at the bottom, the other is a bit more tricky and at the top. I found this very hard to put back and subsequntely tighten. A screw head in a ratchet adapter held by hand proved the best way for me once it was in.

My speakers were 10cm and if you get ones with the 4 corner hols they will drop straigh into the metal plate. I kept the old connector and soldered it to some wire to attach to my new speaker.

In my case the headunit was also at fault, I would check this and the wire first. You can do this with a multimeter on the connector near the speakers, you don't need to remove anything to access these. Make sure your multimeter is set to AC (I spent ages wondering why I was getting strange readings before I realised that for once I wasn't testing a DC circuit!) The voltage should increase as you turn the volume up, my R/H output was pretty much dead.

Hope this is of help to you. Some might say it's more worth your while ditching the factory spaces and fitting something bigger into the doors. I couldn't find the space with the manual wind windows but I'm not sure if the Fourtrak has bigger doors.

Tully