Chainsaw Repair

Oil pump

The Dolmer 122 achillies heel, the oil pump is driven off the crank by a worm gear and pumps using a piston with a cam and spring mechanism, the flat on the end of the piston working as a rotary valve. The pump never wears out but the worm gear pair wear rapidly if engine lubrication is less than perfect and eventually the teeth strip resulting in a loss of bar oiling.

Dolmar modified the pump twice during the 122's lifetime, first the drive end of the pump was extended to form a support bearing (122S) and secondly the whole pump was moved from part of the crankcase to a seperate casting as in the later 123 saws (later 122S & 122SL).

As this saw is an early 122 model it has the early type pump, for which parts are no longer available. Lucky for me the pump was not in bad condition, the worm gear has some life left and fitting it on the crank in the opposite orientation presents unworn gear teeth to the pump pinion. The pump was showing wear but as only the later 122s type pump piston is available as a spare part i had to modify a 122s pump by removing the support bearing with a lathe and increasing the depth and diameter of the spring recess with a carbide drill.
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Thanks for reading :-)

Ade