Front sprocket output shaft

[undead.metalhead]

I picked up a Banshee that is a basket case. I started looking at all the parts I'm going to need and I noticed the front sprocket is welded on and not even a good job at welding it so I have to change the shaft out. I've been looking online and I'm not finding any guides on this. Do I have to split the case to change out this shaft? I have a locked up yz250 motor I'm going to experiment with before tearing into this Banshee motor. I've never taken the bottom end of one of these apart so any guides or videos would be a big help.

[undead.metalhead]

While I'm in there what all should I replace? Seals, bearings etc

[Bennett131]

There is a bottom end walk through stickied, read through that it should give you an idea of what you're doing. Yes, i would replace all seals and at least inspect the bearings. While its apart id recommend having the crank trued and welded so it doesn't cause issues down the road. 

[trickedcarbine]

If you're going that far and actually about to pull all the gears off the shaft, you might as well call around and get a Pro mod transmission. It's not the full over ride like the drag guys run, but it makes trail bikes shift so much nicer.

[undead.metalhead]

This one does seem to be shifting hard I'm just turning the sprocket and moving through the gears but it still feels very clunky and tight. I'd bet they were using regular motor oil and not oil for wet clutches. The kicker doesn't grab everytime either. I think I'm gonna have my hands full with this build so I'm gonna redo everything.