Bombardier SeaDoo 1990 factory shop manual, Page 34Get this manual
Section 03 ENGINE Sub-section 03 (TOP END)
Cylinder Taper
Using cylinder bore gauge, measure cylinder diameter 16 rnrn (518 in) from top of cyiinder to just below auxiliary transfer port, facing exhaust port If the difference between readings exceed specification, cylinder should be rebored and honed or replaced
Clearance can be quickly checked with long feeler gaugeInsert feeler gauge in cylinder then slide piston (without piston rings installed) into cylinder as shown in the following illustration