The early Mitsubishi engine use a small "jet valve'' next to the main intake valve. This small additional valve directs a portion of the air/fuel mixture at the spark plug, allowing hotter and more complete combustion. The jet valve must be removed before removing the larger valves.
The jet valve assembly is screwed into the head. The use of special tool (socket) MD 998310 is required to remove and install the valve. When using the tool, make certain that the wrench is not tilted with respect to the center of the valve. If the wrench is tilted, the excess pressure on the spring retainer may bend the valve stem, causing it to bind during operation. Remove the assembly and set it aside.
| Fig. 1: The location of one of the jet valves on a Mitsubishi
head
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| Fig. 2: Use a spring compressor to compress the valve
spring and remove the valve spring retainers
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| Fig. 3: Once the valve spring retainers are removed,
separate the valve spring from the cylinder head
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| Fig. 4: Remove the valve stem seals with a pair of pliers
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On all heads, install a standard valve spring compressor and tighten it to compress the spring. Remove the valve spring retainers (collets) from the valve stem. A small magnet can be very helpful for this. Slowly loosen the spring compressor and remove the valve spring retainer, the spring and the lower spring washer (spring seat). The valve can now be withdrawn from the combustion side of the head. Use a pair of pliers to remove the valve stem seal from each position. Discard the seals immediately; they cannot be reused.
Each valve should be cleaned to remove the carbon deposits from the valve head and stem. This may be done either with chemical cleaners (wear eye protection and gloves) or with the wire brush and power drill used to clean the head. Do not use sandpaper or other abrasives to clean the valves.
