Method of mounting a timing gear on a crankshaft

A method of mounting a timing gear on a crankshaft having a mounting portion integrally formed therewith, the timing gear having formed therein a bore having a diameter which is made smaller than that of the mounting portion of the crankshaft and a first key way formed in the bore of the timing gear, the first key way being angularly indexed with respect to a tooth of the timing gear, the mounting portion of the crankshaft having formed therein a second key way angularly indexed with respect to a pin portion of the crankshaft, the method comprising:

• securing a guide jig having a mounting key portion and a guide key portion formed therein to the mounting portion of said crankshaft with the mounting key portion being in register with said second key way;
• heating said timing gear to expand the diameter of the bore so that the same becomes larger than that of the mounting portion of said crankshaft;
• mounting said timing gear on the mounting portion of said crankshaft by engaging the first key way of said timing gear with the guide key portion of said guide jig;
• detaching said guide jig from the mounting portion of said crankshaft while keeping said timing gear mounted in place;
• and
• cooling said timing gear to shrink the diameter of the bore so that the same tends to become smaller than that of the mounting portion of said crankshaft thereby firmly mounting said timing gear on the mounting portion of said crankshaft.