Victa Decompressor Troubleshooting

Learn how to Troubleshoot a Victa Decompressor.

Tools/Parts Required 

  • 3/4 Spanner
  • New Decompressor

Step 1.

Check around the decompressor for oil/fuel as this can suggest problems.

Step 2

Next test the decompressor sucking on the nozzle and checking if the valve moves. you can also blow on the nozzle and no air should come out of the decompressor.


  1. thanks for the very helpful video guides, guys.
    It looks like my decompressor is slightly different. Instead of two halves clipped together, mine is a single piece. Is there any way to open it up and replace the internals ?

    • Hi

      Unfortunately those decompressors are not serviceable and there is no way to open them without cutting/grinding.

  2. my victa revs up can’t control revs then it backfires and stops. could be trouble with leaking crankcase?

  3. thank you . my 2 stroke victa decompressor does have oil leaking , but sucking on it the valve does return. I reinstalled it and it started ok then revved up a bit then I adjusted the throttle so it didn’t over rev,and I ended cutting most of my lawn, then all of a sudden it revved up and stopped, then it wouldn’t start.

    • Hi

      Oil leaking from the decompressor is a sign that it is not working as well as it should be. Suddenly revving up & stopping is a common symptom of carburetor problems, This happens most often because the mower cannot get fuel as the mower staves of fuel the mixture becomes lean causing rpm to increase before it completely runs out of petrol.

  4. Very useful videos.

    I suspect my decompressor may be faulty as the starter meets almost impossible resistance during the engine cycle. Removing either the decompressor or the spark plug eliminates the resistance. Also, pushing the decompressor valve out by using the blunt end of a pencil on the vacuum tube side of the unit allows the starter to turn the engine normally.

    To my mind this all points to a faulty decompressor, but what puzzles me is I’ve seen reference to work-arounds by replacing the decompressor unit with a spark plug. The article that suggests this says it will make starting a little harder, but in my case the resistance is so strong it’s effectively impossible to start.

    Am I missing something? I’d happily order a new decompressor if I could be confident that would fix the problem.

    • Hi Norman

      This a a relatively common issue and there are two main causes, The most common cause it that you either do not have the blade carrier and blades fitted to the mower or you have the blade carrier improperly fitted.

      The blade carrier and blades must be firmed secured so that the blade carrier cannot rotate without the engine also rotating. With the blade carrier loose the engines timing is incorrect and the mower with try to start in reverse this makes it extremely difficult to pull the starter cord.

      If you blade carrier is firmly fitted than the decompressor is usually the cause of the issue.

      • Thanks for your reply on the above comment, it solved the pull cord resistance problem I had, I checked the decompressor and it appeared to be working okay.
        So I checked the blade carrier which I thought was tightened okay but after closer inspection I found there was a slight vertical movement on it, so I started to undo it and found the nut had loosened ever so slightly, after undoing it and resetting it voila the problem went away and the mower started without a hitch.

        • Mr anonymous. The blade disc nut MUST be tightened up at 55 foot pounds with a torque wrench otherwise the blade disc can come loose or come off completely during use and you or someone else will be severely injured.

  5. Hi
    Is the decompressor just for easy start or does it effect engine revs?
    My imperial starts and idles but as soon as you go to rev it up it backfires and stops, I’ve cleaned the carby but still is happening.
    Any ideas?

    • The decompressor can effect the engine if it is damaged, A simple test is to remove it and replace it with a used spark plug then test the performance of the mower.

  6. Hi, my lawnmower won’t start, I noticed black oil near the decompresser, but I trouble shoot the decompresser like you have shown, and seems to be fine, could it be something else?
    Thank you very much appreciated.

  7. Winner! Thanks for the video. Compressor was broken just as in your video. So, I have ordered a replacement from your company. many thanks.

  8. Hi, my mastercut 460 is pulling without the rev bar engaged and when I pull the bar, it rips my hand back into the mower with the compression, like a jamming kickback. I had the decompression valve off for inspection. The valve was slow and stuck once pushing it and may have done damage spraying carb clean into the holes in it thinking I was cleaning it, also blueish smoke firing out around it or the head

    • Getting the cord ripped out of your hand is usually either decompressor fault or the blade carrier is loose or not installed.

  9. Hi Lachlan,
    Regarding the decompressor on Power stroke engines, I had the internal packing fall out when I cleaned the unit & blew it out. Could please advise if this will cause an issue?
    Thanks in advance,
    Cheers mate,

    Gleen Fonti

    • Hi Glenn

      Without the foam there is no filter on any air which may get sucked into the engine during the intake cycle so short term is not too much of a problem, Over the long term you will get more dust sucked into the engine which would contribute to faster wear then if you have the foam in good condition.

  10. Hey there, i have an 2 stroke victa which both has surface rust and still runs. one day while I was mowing my back lawn. halfway done, my lawnmower was not running properly and it even stalled. it was hard to start, when I got it running, I looked at it for a bit while idling like crap and when I saw it backfire through the decompressor, I replaced it from my other victa which was for parts. i thought it would run better but It did the same thing! while I ran it, I pressed the bulb a couple of times, it ran fine then ran like crap again and realized, do I have a vacuum leak or what? I replaced the spark plug, still doing the freaking same thing! and I know people which have similar problems to my victa, it was running fine and it even idled fine before it even happened.

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