OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Victa Two Stroke Engines Victa Decompressor Valve - Rebuild How-To

G'day folks,
As there doesn't seem to be a detailed procedure for this on ODK, I've decided to write one. So here goes.

One type of Victa decompressor valve, the 'long' type P/No EN72135, as fitted to the full-crank engines, is now NLA from any trade supplier. So rebuilds will become increasingly necessary, to keep these older mowers running.

As part of a minor overhaul of a 160cc full crank engine that I currently have as a 'work in progress', the deco valve will be rebuilt, using a rebuild kit supplied by the ODK shop; it's HERE

Here's the deco valve, as removed from the engine. NB: Only deco valves [like this one] which have 3 spring clips around the periphery of the diaphragm chamber can be rebuilt. BTW, removal of this valve requires a 13/16" AF open end spanner. The later short types have a 3/4" hex.



The white nylon 'decompressor nozzle' often doesn't survive having its hose removed, and this one hasn't. However, black nylon replacements are available, cheap, and now listed by the ODK Shop HERE.

Next step is just cleaning up the valve in the parts wash, so I won't put up a pic of that...

Part 1 Dismantling/Cleaning

First step is to pry off the 3 clips. This has to be done with care, as these ones are the original 'jesus clips'.
Those are the ones that cause one to exclaim 'Jesus, where did that go', as they fly off to who knows where.

A sharp pointed scriber is my tool of choice.



It is used as shown, under the outer edge.

NB: It is only shown facing the camera for clarity; this job is best done with the clip facing away from you, pointing towards a catch container, or backstop, to trap any flyaways.



First view of the valve innards.



The valve components, arranged in order of removal, top to bottom, then left to right and up. Note the carbon deposits visible on the stem of the poppet valve. The foam filter is generally cactus; a wipe with a petrol soaked rag will help in removing any sticky remnant bits of it.



The retaining clip at the top of the poppet valve stem is trickier than it at first seems; it has an inner flange to lock it into the small spring. To remove it, the small spring has to be compressed a bit first. The points of a pair of dividers work well here.



The poppet valve; cleaned up by wire brushing. I used a vise with soft aluminium jaw covers to hold it during this process, and a hand wire brush.



It's also worth de-coking the valve bore above the poppet valve seat; a 9mm or 23/64" drill bit is a very good tool for this job. This valve wasn't at all badly coked up; we used to see much worse, back in the days of BP Zoom 25 pre-mixed fuel.