X2 Truebluemax.
And yes, you need 1/4" spacers on each side up front and you have to shorten the rear AC cross shaft which is pretty easy. The amount depends on what you use for drop brackets (aluminum or steel, thick or thin)
For positioning, I used TBM's measurements as a guideline to get me in the park. The key here is make sure you are at least 1.75 higher (Y dimension) than stock because the approach angle is so low on the AC rails. You need to draw a straight line between the centerline of the front suspension shaft bolt hole (in the tunnel) and the centerline of the drive sprocket. That's what all of my X-Y measurements are based on.
In terms of moving the front suspension axle forward, 2 inches will work and give you lots of space to adjust your track tension but be careful with this. If you go too far forward your rail tips will be pushing into your track. I am very tight on this measure at @ 1-1/4". CAD says I can do it, but I know I am very tight. So somewhere between the 2" and 1-1/4" should work.
Also, my measures assume 2 things:
1) you are using the stock AC 153 rails that have a 21 degree tip up (that's what mine measured, not 18 as advertized in AC literature, but its almost the same as timbersled (22 deg) with iceage rails and the new design Yamaha (22 deg). My measures will work with the iceage rails too.
2) you are running the stock yami 7 tooth, 3" pitch drivers, or any aftermarket with the same 7 x 3 spec. A bigger driver will change the spec.
In terms of the back drop brackets, the key is the distance between front and back axles needs to be 31.25". Mine are up 2.00" (Y) and ahead 1.55" (X), and this is tied directly to how much I moved my front.
Finally...Two other considerations
1. Anti-Stab kit, Anti-Stab kit, Anti-Stab kit. You don't... you'll be short a track sooner or later....usually sooner.
2. this setup moves your track a bit higher in the tunnel, approximately 1-1/8" so if you are running an undertunnel, make sure you have the necessary clearance to protect that investment.
I am right in the process of doing this install, having just got my tunnel back from the painters. Hoping to finish it in the next week or so. I'll post pictures once finished.
OTM
