The bumping clearance can be checked by the following methods:
1.In case a suitable opening is available the piston can be barred to the top dead centric and then feeler gauges can be put inside and the clearances checked at two three points.
2.The more convenient method is to take lead wire from the engine store and make a small ball based on the expected clearance and put it between the piston and the head from the valve opening. Then the piston is slowly turned to the top dead centre with the help of a Tommy bar. After that the piston is again turned down and the lead wire ball is extracted and the thickness measured with the help of a micrometer. This measurement would give the bumping clearance.
The caution which must be observed in these methods is that the clearances of the main and the crank pin bearing have not been taken into account. The correct method is thus that after turning the piston to top dead centre the piston connecting rod must be jacked up with the help of a crow bar. It is only after this hidden clearance has been accounted for, will the correct bumping clearance be found.