Yamaha MT-09 (’21–’23) — Seat Slope Mod Install Guide

This guide covers installing the Yamaha MT-09 (’21–’23) Seat Slope Mod (Gen 3). It shims the shared tank/seat forward bracket up by 6–8 mm to level out the front of the seat, and includes optional eccentric rubber bushings that keep the tank close to its stock height.

Before you begin

• Not a confident wrench? The install is simple, but if you’re not comfortable with this kind of work, have a qualified mechanic do it.
• Do this with the fuel tank mostly empty. You’ll unbolt the rear of the tank, where most of its weight sits. A full tank feels like it won’t move — this is the #1 source of support emails.
• Take photos before you start. A simple mechanic’s trick to remember how everything looked and make sure nothing’s missed.
• Some photos are from pre-production runs — minor items have changed (e.g., the top bolt washers now ship as small washers instead of large shoulder/fender washers).

How it works

There are two parts to this kit. The seat-bracket shims raise the seat mount by 6–8 mm to level the seat. The eccentric tank bushings (optional) shift the tank bolts down in their holes, lowering the tank by 3–4 mm so it stays near stock height as the seat goes up. The diagram below shows the stack layout.

Installation steps

1. Put the bike on a stand — a center stand is ideal. A side stand works but is harder, since the rear of the tank wants to shift to the downhill side.
2. Unbolt the two tank bolts and remove the metal sleeves from the OE rubber bushings — keep the sleeves. Support the tank with something soft (like wood blocks) so it doesn’t sink onto the frame.
3. Unbolt the four seat-bracket bolts. Keep the OE bolts for a possible return to stock — they aren’t reused in this kit.
4. Swap the bushings. Take the bracket off, push out the OE rubber bushings, and press in the JK3D eccentric bushings — flange toward the tank, with the offset hole at the bottom (6 o’clock). Push the OE steel sleeves back in. (Gen 4 only: if the seat won’t align, try the eccentrics flange-side toward the seat for more clearance.)
5. Reattach the bracket to the tank. Set it back on, align the tank, reinstall the OE tank bolts, and torque to 7 Nm.
6. Build each shim stack: washer on top → 6 mm shim → optional 2 mm shim.
7. Slide a shim stack under each side. Gently but firmly grab the bracket by the center and slide the stacks in. A second person helps here because of the tank weight, but it can be done solo.
8. Insert the kit’s 6 mm bolts (with washers), thread them into the frame by hand, and snug them for now.
9. Install the seat and check the alignment and feel. (Gen 3: don’t accidentally use the upper slot when seating the bracket — it can make the seat unstable.)
10. Final torque. Once the alignment and height are right, remove the 6 mm bolts one at a time, add a small dab of blue threadlocker (never red), and torque to 12 Nm, working in a cross pattern so the bracket stays centered on the frame.

Adjusting the height: if the stack is too tall, remove the 2 mm shim and re-torque. If the tank is lifted higher than you’d like, use the eccentric bushings (Step 4) — they drop the tank 3–4 mm to offset the seat rise.

After the install

• You may want to tweak your handlebar angle to match the new seat position — do a little testing and fine-tuning.
• After a couple of months of hot-weather riding, recheck the frame/bracket bolts for any play.