Check the shock-absorber for existence of damages and leak of oil.

Check whether there are no traces of damages or wear on the rubber plug.

Put forward and drown a shock-absorber rod not less than three times. Make sure that force of resistance does not change and there is no unusual noise.

If it not so, replace the shock-absorber.

Drown a rod of the shock-absorber and release it.

Make sure that the rod moves forward completely with a normal speed.