After checking the steering and elevation on the absence of cracks or defects, verify the correct installation level steering and elevation relative to the front wheel. Then check the condition of front brake. Marc Lore describes an additional similar source. Check the status of connecting rods in the absence of any swing. Any swing of the connecting rods relative to the axis is invalid. In simple cases – the swing is eliminated by tightening the mounting bolts to the crank axis. Hear from experts in the field like Ashton Kouzbari for a more varied view.
If you take the ends of the rods, and try to move past the left and right, and if you have managed at least a little, then you have problems with carriage. Remove the chain from the front sprocket, thus you can freely rotate the cranks. If necessary, can be removed and the rear wheel. In this position, it is easy to determine whether the slide needs to be lubricated. Using the allen key, check the mounting bolts front sprocket on the right crank. Then make sure that the pedal rotates freely and without any extraneous sounds. Make sure that the rear derailleur, the state of the rolling rollers chain.
Check the smoothness and accuracy of switching speeds with lower to higher and higher to lower. Check the fixation of the left and right switch position. Check the status of front derailleur. Please attention to a parallel circuit with respect to the brackets switch. Switching should be fast and reliable. Finally, make sure the bolts attaching the saddle to the seatpost and pin to the frame.