XS400 ATV

[79xs]

Looks to be just where you want it to be IMO. How is the angle of the seat?

I'm thinking of cutting out the factory swingarm mounts and moving them up on my build just so I don't have to come up with something for my chain routing since I didn't drop the engine through the frame and the engine sprocket is way above the pivot.

It's really a hard frame to start with, but it's also good practice. Depending on what I do for a fuel tank I may end up tweaking the rear sub frame to fix the seat height. I checked out your build photos on the other site. I would bring up the pivot points for sure. Due to the swing arm angle you might be able to make up your whole height difference by extending the swing arm. Also, I have no idea if the size is even close, but a 1989-94 or so FZR 600 fuel tank has the same general shape as the one you are making.

 

[79xs]

Small update. All lower mounts are mocked up.

 

[rshutchinson]

The only thing with moving the pivot up is I would also need to move the upper shock mount up as well if I don't want to throw everything else off.

I've got an idea for the chain that I think might work so I'll look into that later. Anyway,enough about mine.

How much is left until you're ready to ride this one you think?

 

[79xs]

A lot is left to do. I am using this build as practice so I'm making sure not to rush myself.

Tonight I cut the front half the frame to add caster back to the a-arm mounts. I fully cut the frame near the front fuel tank mounts. I then slotted the top of the lower frame tubes. I used a ratchet strap to pull it until the angle matched that of my other stock frame.

Sneak peak mockup

Oh and I'm now 100% sure the rear sub frame will need to be rolled back.

 

[79xs]

It's been way too cold to work in the garage. I have been thinking about the exhaust a bit...

There is a very cool build on this site with a XS400 motor in a enduro. In that build they used 1.5 inch OD pre-bent exhaust tube from Summit Racing for headers. They only cost 13 bucks and kept the pipes tucked up next to the motor. I really liked it.

The only item I wasn't sure about was the tube size. 1.5 inch tube is indeed a perfect match for the stock exhaust OD and flanges, but since the stock exhaust is double walled it has a stock ID of 1.200 (give or take) At 16 gauge, the summit racing tube would have an ID of 1.375. I'm thinking of going with 1.375 OD, 16 gauge tube from summit that will leave me with a exhaust header ID of around 1.250. Any input?

 

[Wolfe_11B]

I used the same 1.5 od bends to do my exhaust. Worked well. You'll be fine either way. I just didn't want a visible size difference when transitioning between the two, so that's why I chose the 1.5

 

[79xs]

It's warming up outside so I started working on this again.

I used the same 1.5 od bends to do my exhaust. Worked well. You'll be fine either way. I just didn't want a visible size difference when transitioning between the two, so that's why I chose the 1.5

I'm just worried about losing some low end torque. I have access to a lathe so I could always cut some custom flanges. I'll have to think about this a bit.


In other news, rolling the front half of the frame back fixed all rear shock issues issues. I will not need to make any changes to my rear shock mounts. A slightly longer 400EX shock is all I needed to level it out. Now, I have to decide if I'm going to use a 2.5 gallon tank under the seat or try and do a custom tank over the motor.

 

[rshutchinson]

How big can you make a tank fit over the engine?

 

[79xs]

The tank can pretty much be the same size as the stock tank cover. It just can't dip between the frame tubes like the stock tank did. I don't have an A/C tig so it will have to be steel.

 

[rshutchinson]

I made mine out of 16ga steel using flux core. Some holes but sealed up best I could and then used seal-all on small pinholes that wouldn't close up.

 

[rshutchinson]

Any updates?

 

[79xs]

None on this.