Replacing Tensioning Check Valve

The purpose of the check valve (2) is to prevent the saw chain from becoming slack from external obstructions e.g. undergrowth. If this function fail, the check valve (2) or the spring (3) may have to be replaced or disassembled and cleaned. To replace the check valve and the spring, do as described below.

Before performing any maintenance or service work, lower the attachment to the ground and shut off the engine. Turn off any master shut-offs and do not allow personnel in the cab. Remove the saw chain.

When working on the saw chain always ensure the engine is shut off and wear safety gloves to prevent injuries. Remove the saw chain when making any adjustments or servicing the saw unit. Loosen the fasteners (1) and pull out the Pilot Valve (2) Remove the check valve (2) by using the installation tool, P/N 0690149. Remove the spring (4). Install the new spring if required. Install the check valve by using the installation tool,

P/N 0690149. .

If using a normal hex key to install the check valve, this may cause the washer on the back side of the check valve to fall off and disfunction the check valve. If this happens, make sure that the machined surface of the washer is facing the check valve when reassembling. If a little grease is applied to the washer, it will stick to the check valve when reassembling. Test the function of the check valve by pushing it with e.g a small screw driver. The washer on the check valve must be able to move approx. 0.5mm Install the pilot valve (2) and tighten the fasteners (1) Install the saw chain.

Fig. 27Replacing check valve - Saw activated tensioning Fasteners, 2 pcs. Pilot Valve Check Valve Spring

Fig. 28Pilot Valve - Saw activated tensioning Fasteners Washer Plunge O-ring

Fig. 29Check Valve Assembly