Victa G4 Carburetor Service

In this tutorial we will be demonstrating the service of a Victa G4 caburetor

Tools/Parts Required 

  • Flat Head Screwdriver
  • Phillips Head Screwdriver
  • G4 Carburetor Service Kit

Step 1.

We begin by turning off the fuel tap and removing the top cover.

Step 2

Once the carburetor is exposed we can remove the front plate and inspect the float, jet and seal and replace any parts that are damaged. It’s important that all parts are well cleaned before reassembly – a faulty float or jet will cause fuel to leak out the primer bulb.

Step 3

Once the front of the carburetor is reassembled you may proceed to inspect the body. After disconnecting the carburetor from the engine, carefully remove and inspect each part replacing those that are broken. The diaphragm is commonly the problem and the first thing to replace – it’s sometimes hard to tell whether it’s damaged (tell tale signs have been shown in video to make this easier).

Step 4

Reassemble the carburetor, making sure all parts are clean and that none are damaged.


  1. Hi,
    I had a leak and replaced the seals as described in this video. This fixed my leak problem but now my victa won’t shut off. I have to turn the fuel line off to shut it off. Can you help?

  2. I’ve been having trouble with one of these, its a Mustang from about 1987. Previously it would not start at all now it starts but won’t continue to run. I’ve replaced the float needle, faceplate and the diaphragm which had a small split in it.

    • It sounds as if there is a problem with fuel continuing to get through the carburetor after initial starting, there is a few things that can contribute to this, firstly i would check fuel flows freely through the fuel tap as sometimes this
      can be blocked or the fuel cap can breather can be blocked.

      if this does not solve the problem your lower Crankcase seal may be leaking causing a lack of vacuum in the combustion chamber which affects the engines ability to draw in fuel.

      • From the video it says that the wires should not be contacting. Mine aren’t contacting – I’ve installed all new rubber bits around the wires and they’re definitely not contacting.

        Would you be able to tell us what the actual problem is? I don’t really want to install a kill switch and would prefer if everything was completely original.


        • I’m not sure if the issue I’m having is the same as the original poster – the throttle was working fine before with the kill working when the throttle position was at “STOP”.

          But now the mower idles when throttle position is in the middle (sounds like it’ll kill but it just idles) – and when I move the throttle up or down it appears to increase the throttle.

          Is this a common problem? And what is the cause for it?


          • If your kill switch is not shutting off the mower when you move it to the stop position and is instead increasing the revs if means your wires are not making contact. this leaves the switch open and does not turn off the ignition. This is common and can happen if the wires are seated to far into the carburetor or too little. The mower should idle in the middle and rev and normal speed when are full throttle.

    • Had the same issue – If the mower will not continue to run check the float needle it may be the wrong way around – that fixed my mower

  3. Hi

    I removed the Cam, i am having trouble connecting the throttle cable back onto the cam

    any tips? or if you could make a video how to do this would be great

  4. Hi
    I wasn’t sure where to post this but i thought this might be alright since it has to do with the carby, i have a victa corvette 600 and for some reason it starts but cant be revved to high because it stalls however if you close the intake pipe it starts running fine. Any ideas what this might be?

    • Hi

      When you close the intake pipe are you completely cutting of the air supply? It sounds like your mower has a air leak causing it to run to fast. You will need to check all the O-rings, and check the intake pipe and carby body for cracks, Air can also be drawn in from damaged crankcase seals

  5. This is a great video-very easy to understand and well filmed.

    Quick question…I have a Victa 160cc 2 stroke that has a carby that looks like this G4 one.
    I’m trying to remove the carby from the main part of the engine, but when I twist the carby 25 degrees it won’t slide off. I can see the two plastic ‘clips’ that normally hold it in place have moved to the position where the slots are wider but it just won’t budge.

    Is there a trick to it or maybe something else that I need to loosen?

    I’m going to replace the diaphragm etc.

    • You may need to twist the carby further, Once it is twisted enough it should be free from the locking tabs and able to be pulled off, they can get a bit stuck if they are dirty or have not been removed in a long time

  6. Hi there.

    I have found that when the breather hose is disconnected from either the carburetor or the body of the mower, the revs increase significantly – I estimate it over doubles the rpm. Is this normal?

    • Yes this is normal, By having the intake removed you are allowing more air into the engine causing a lean fuel mix this leads to much greater rpm and can lead to engine damage from lack of lubrication if the fuel mix is too lean

  7. HI! I just finished cleaning my curby but after installing back everything, it only runs in 1 speed now . Even if I move the lever all the way up or down it stays in the same speed. But if you put it slightly before the Run position, it slows down a bit, What could be the problem? I have checked the connection of the cable again and it sits the way it should be. Also I installed an external kill switch to turn of the engine. Pls, Help Thanks!

      • Thanks for the prompt reply. Will check possible air leaks and will block off the hole from the old switch. Currently it’s not overreving, its just that the lever is not functioning as it used to be before cleaning the curby. Will be back after doing your advice. Thanks again!

  8. Hi,
    Iam going to fix a leak in my primer. The seal needs replacing – which I will do but when I go to place the screw back in it doesn’t tighten up but when I try it without the cover on its tightens without any problem. Damned if I know whats happening. Fuel also flows out through the primer cap hole – could this be because the scews not tighteneing or is my float faulty?

    • Hi

      if the screw tightens without the cap on it should also tighten with the cap on it may just be a bit temperamental to get it started, It does not need to be too tight as the thread is plastic and can be easily damaged if tightened too far. Fuel coming through the primer cap hole is caused either by a faulty needle or float not properly sealing when the fuel reaches the correct level

  9. G’day Mate….
    Good videos and simple to follow. Anyway ….just wondering, I’ve replaced the carby white side cover and needle coz my bulb was leaking…now it doesn’t want to fill up the carby. It runs if I put fuel in the cylinder. I prime the !^@$# out of it and it and I can see through the plastic cover it only fills up to about less than 1cm. I haven’t had a go at taking the carby apart yet but the original problem was just the cracked primer bulb. ( that was almost 2 years ago and am only just getting stuck into fixing it) .Yeah, I put in a new needle and white side plate , bulb and “o” ring…….Just seems to only want to go for a few seconds and run out of fuel. Prime the hell out of it again and it will go again.
    I’m hoping I will find a problem with the diaphragm or something.

    • Hi Mick

      The fuelling issue is most likely to be caused by the float and or needle, Both items have to be able to move freely, Sometimes there can be rough edges on the float of needle, A light sand will usually remove them and allow better movement. It is also worth checking that the copper seat in the primer cap is correctly seated, They can sometimes dislodge and this will effect the fuelling. To check it use a screwdriver or small bolt to push the seat it will move further up if it is dislodged. The seat is located where the needle goes in the primer cap.

  10. Hi,

    Thanks for taking your time to providing these tutorials.

    I have a Victa MSP-462 Mastercut mower

    I inspected the float, jet and seal which had been recently serviced. All in good condition

    I found excess fuel inside which was milky white; all drain out when I pulled out the cover.

    Having all parts in place again and screw, the mower managed to start-up with little pulling effort.

    After cutting lawn fuel 30min. , fuel ran out so turned the tap in the off position.

    After giving a 10-15 min to cool I then refilled tank. when I turned tap to on position and was priming the mower, I noticed fuel started leaking just under the carb. itself.

    Was unable to get it started again and mow.

    Is there something that I missed or did I only solve only part of the issue?

    • Hi Tomi

      The mower should not need to be primed after sitting for only 10-15 minutes, priming could have flooded the engine, When you say leaking under the carb, could you determine which seal the fuel was leaking from.

  11. Hi,

    I forgot to turn the fuel tap off after finishing, now my mower isn’t the same anymore. Normally I’d wait a day after turning it off and it goes back to normal, but now it’s completely not working 🙁

    I’ve cleaned out the carburetor, replaced spark plug, new fuel, and added fuel into the spark plug hole and it went back to working like new again. Next day I take it out it’s not working anymore! Now I get this hissy noise whenever I pull the cable to start it. I checked the decompressor and it seemed to be fine but I wasn’t sure. Argh help!

    • Hi Pat

      The hissing noise sounds like you may have blown out the head gasket and thus have lost compression, It is a simple process to remove the 4 bolts in the cylinder head to check the condition of the gasket.

  12. Hello,
    I’ve had running issues for the last few weeks and after replacing the head gasket I have also replaced a few parts on the carb. New diaphragm, needle and cleaned out the insides of the carb.
    Then the carb flooded and this killed the spark plug so bought a new spark plug and it started up. Then after 30mins of mowing I stopped to move to the front lawn and it wouldn’t start again along with the carb flooding again.
    I’m still getting spark and have cleaned out the float bowl of the carb again but she just won’t fire this time and floods but not every time.
    Also, the area around the decompression valve gets oily black. Is this normal?


    • Hi Mike

      When it was mowing did it seem sluggish and very smokey? It sounds like the mower is running too rich. Which parts have been replaced in the carburetor

    • Hiya,

      It was sluggish until it had warmed up and is always fairly smokey on start up but less so once warmed up.
      When emptying the grass catcher so the mower is stationary but running it will increase the revs as it sits there and I have to throttle it down.
      I did a full service kits last year so all the ‘O’ rings have been replaced. The diaphragm was replaced at the same time but has been renewed during this bout of trouble shooting as the replaced one had already lost it’s shape on the outer edge. The springs on both side of the diaphragm are in great condition. It’s also now runnings a yellow needle isn’t of the black as even a new black needle made the float hit the primer cap.
      The mower is easily 15yrs old and until I took ownership hadn’t really been serviced very much, if at all, in those 15 years.
      I’m wondering if it needs a new primer cap?


      • Hi Mike

        A new primer cap would be the next logical step in the troubleshooting process as flooding issues can be cause by a worn out cap.

  13. Hi, i have an old-ish Victa with a G4 carburetor that has worked ok for years. I recently cleaned out the cylinder head and serviced the front of the carburetor, replacing the seal and the needle. Now the mower starts ok but goes through a cycle of revving up and revving down every ten seconds. When it revs down it often cuts out altogether but if i stop mowing it will usually rev up again, only to rev down again after ten seconds. Very frustrating. What have i done wrong?

      • Awesome thank you. I didn’t get far with mowing today. Looks like next Thursdays job is rebuilding a carburetor!

  14. Thank you for the excellent tutorials. I have a VICTA 140cc Super Catcher lawnmower.
    It has recently started surging. I am guessing this has something to do with the carburettor?

    • Yes surging is most often carburetor related. A clean and service should reveal any issues present

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