Note: When in mid air and holding the gas, the bike will tip forward a little when you hit the brake. This "trick" is used a few times in this solution
I used the Scorpion for this.
Start: Gun it until you hit the ramp, then brake to stop. Roll back until your front tire hits the flat of the the ramp, then gun it again. In midair tap brake. You should land straddling the bridge. A little gas will get you to the checkpoint.
1st Checkpoint: Light gas until the top of the rise, then pump the gas to get to the valley and the next checkpoint.
Alternately you can maintain momentum over the rise like I did in the video.
2nd Checkpoint: After the flat, go full on with the gas. at the very top of the ramp tap the brake. this should give you a flat landing if done properly.
3-6th Checkpoint: This one is tricky. you need a little speed to avoid getting your front tire stuck, but not so much coming off the flat that you topple. A short burst of medium throttle should do it. Coast down to the 4th checkpoint and when your back tire crosses it, gun the gas again. Keep gunning it until you pass the water.
7th Checkpoint: Easy on the throttle going up the steel ramps. **do NOT hit the brake in midair here.
8th Checkpoint: Easy on the speed until the bike tips down, then gun it until you do a small jump. Then just go easy on the gas until the next checkpoint.
9th Checkpoint: Use medium throttle up the ramp. Do not go for the shortcut up top, instead land safely below. Gentle throttle to the next Checkpoint.
10th Checkpoint: Gun it up the ramp, then let go of the gas until you land. **Do NOT hit brake in midair.
11th Checkpoint: Easy on the throttle until the next checkpoint.
12th Checkpoint: tap the gas to get off the platform, then easy gas up the ramp, then gun it as you start down after the crest.
Alternately you can get off the platform, then gun it to the end.