Victa G4 Carburetor In Depth Guide Part II

Learn how to correctly assemble a g4 carburetor

Tools/Parts Required 

  • Flat Head Screwdriver
  • Pliers
  • Carburetor Cleaner

Step 1.

Insert the cam back into place and ensure that it is moving correctly,  and make sure that it does so with relative ease. Turn the cam clockwise as far as it will go and then begin to reinsert the throttle cable – thread the cable into the appropriate grooves to hold it in place and slot the gold ball at the end of the cable into the cam (having the throttle in the off position makes this easiest).

Step 2

Next re-install the ignition wires by first turning the throttle to the middle position then place the cover and plug over the wires and insert the red wire through the hole in the body of the carburetor where it is supposed to go, push the cover flush against the carburetor body. The second ignition wire will be inserted at 90 degrees to the first, you will notice there are holes in the cover for this wire to be threaded through.

Step 3

Place the poppet valve through the designed hole from the bottom of the carburetor body, the pointy end should protrude from the hole in the centre of the cam. With the poppet valve in place you can now place the lifter in position – the lifter has written on it which side is intended to be place down – its three prongs slot into grooves on the inside of the carburetor body.

Step 4

Place the small spring into the grooves on the lifter then place the diaphragm over the pointy end of the poppet valve, it should clip in place – the shiny side of the diaphragm should face upwards. Also clip the metal retainer onto the end of the poppet valve – the flat side of the retainer should face down.

Step 5

Now we can move to the front of the carburetor – inspect the primer cap and ensure there aren’t any cracks or missing pieces (check the primer bulb too). Place the primer o-ring around the sides of the primer cap – as you do look out for any breaks or cracks in the o-ring. Place the small jet into the primer cap with the pointer end down then hook the float in place – when pushing the float up as much as possible the small jet should limit its movement; if this isn’t the case then the jet will need to be replaced.

Step 6

Move the primer cap and all the bits we have now attached into position in the front of the carburetor body, there is a line on the front of the primer cap which indicates the correct orientation of the primer cap – if the carburetor leaks petrol when reassembling this orientation is the first thing to check. Clean out the main jet and the screw the primer cap in place – gently tighten the main jet so as not to thread the plastic primer cap.


  1. Whew! what a job I’ve been having recently with my Victa, owned for the last 23 years!! with very little problem, however recently the decompressor valve went, I replaced it along with the carb diaphram and changed the kill switch to a manual.

    Now I can get the engine to run but its so erratic, can you confirm 2 things here,

    1. Is the carb needle definetely pointy end down, this seems so wrong as one would expect this to seal the fuel, but happy to be proved wrong.

    2. I have a spare brass fuel jet which has no hole on the “outside” and another which has a small hole in the slotted part of the jet, which one is correct? the holed one is original and ran fine for years but now lets fuel leak out, perhaps if the needle is the wrong way around.

    I also replaced the head gasket as a matter of course.

    Its been a brillaint piece of equipment and I think its something minor to sort but just cannot seem to get it running smoothly.

    Any help would be appreciated,
    from Scotland UK

    • Hi Rob

      1. The carby needle is pointy end down (Or Pointy End towards the brass seat) This is what creates the seal when the float rises.

      2. Where does the fuel leak from the primer bulb or the jet? There should be a hole in the shaft of the jet and a hole in the end that sits inside the carby.

      If it’s running very fast you may have air leaks causing a lean mix, you should cover the whole the original ignition wires resided in and check the air hose for any leaks if this is happening.

      Any further details about the behavior of the mower would help me suggest solutions.

  2. Dear Lachlan,

    Thats a real scottish name from here no doubt you will know your ancestory.

    Anyhow have managed to change the carb needle to pointy end facing the float, replaced both float and needle.

    I’ve changed the jet to a “non holed one” ( in the original outside slot, think it has just worn through from the inside) which I’ve now changed. Fuel was coming out of here but not the primer bulb.

    I used araldite on the old kill wire grommet hole on the carb body to seal following your advice about perhaps it might be air getting in. No diference

    Checked and changed the diaphram.

    Checked both carb springs look fine.

    Checked the operation of the throttle cable, it does move the cam inside the carb its OK with full movement.

    Checked the rubber ring at the inlet manifold its OK.

    The air filter is old so I removed it just incase it was clogged, no diference so placed back in.

    Changed the decompressor valve which was needed, now that bit is perfect.

    Fuel is getting through from the tank OK, checked the air inlet on the tank cap, its OK.

    So, I can get it started easily enough I keep gently pressing the priming button, if I dont keep priming it just conks out after about 20 seconds.

    The revs stay pretty much on the high side, I tried to move the inner rod to position “A” and tried the other positions too but no change.

    Tried changing the body of the carb with a second hand one — no diference.

    I’ve had many motorcycles over the years and still do all my own car maintenance so I should be able to sort this one out but cant it would appear!!!

    The air hose next to the carb could do with a wee tighten up but I have run carbs on bikes before with no air filter so I didn’t think this would be too much of an issue.

    Now at a complete loss…………Grrrr

    Any help would be appreciated

    • Hi Rob

      The pointy end should face the brass seat in the primer cap not the float.

      You have checked most of the important pieces, The symptom of the high rev’s tends to happen in a lot of aging Victa’s, When all parts look and seem to function fine the best technique to slow them down is to use 1 or 2 of the brass poppet valve spacers we sell.

      The air hose being loose probably won’t make much difference, I experienced a mower with very similar issues about a month ago, I replaced the carby body to solve its issue.

      If it keeps running while priming there is two more things I would suggest checking, Get a small needle or wire and poke it through the hole in the carby body that starts where the main jet screws in and exits into the main body of the carby, this hole can sometimes get blocked.

      The other sugguestion would be to check the seal under the pull start and the sealed bearing at the bottom of the crankcase, Because if the carby is working and not blocked the only reason fuel would not make it to the combustion chamber is a lack of crankcase vacuum due to busted seals.

  3. Ok thanks again for your help Lachlan,

    I’ll give your suggestions another go and see how I get on.

    1. Given that I’d changed the carb bodies previously it may not be a blocked hole , but I have carbon depleting EGR valve spray I used on my car I might also give that the once over while in there with the fine needle.

    2. I had the pointy end in the right place to begin with will now change that back following the advice.

    3. I’ll get back to you once I’ve carried out the checkes on the seals, are these available to buy from you guys these days?

    Your help and guidance is very much appreciated.

    Kind regards

  4. Hi there

    I cleaned my carb and the mower would not start. Then I loosened the carb and it started. Then I noticed that if I just kept to carb close to the manifold it would run,but as soon as I would fit the carb. Then the motor would smudder and stop.
    Any idea what could be causing this?
    Thanks Nuno

    • Hi

      it sounds like your mower is being choked by lack of air flow, I would inspect your air filter and make sure there is not blockages in the hose connecting the filter to the carburetor.

  5. Great advice. You didn’t mention if there are two float valves (yellow and black0 I had an old black one in and got sold a yellow one – still won’t start. Got spark but a problem with fuel getting in. All new cover, needle and float. Could it be the screw that holds it all together?

  6. G’day,
    Great work with the website.
    I’ve stripped the carby and degreased it. I noticed what appeared to be grease on the internal moving parts, mostly between the cam and body.
    Did these come greased from the factory and do I need to re-grease it on reassembly?
    Cheers, Adam.

    • Hi Adam

      Either some 2 stroke oil or a small amount of grease can be used between the cam and the body, This will help ensure the throttle cable is not sticky when the carburetor is reassembled.

  7. Hi. Dr. Victa,

    My VC 300 has had all of the above easy bits serviced but still refuses to fire up.
    I have now checked the large O ring under the pullstart wheel–seems OK, but won’t start.

    Strange thing, when I remove the new sparkplug & pull the Cord the cord yields smoothly & steadily all the way to the 1m. of its length.
    But replace sparkplug & the Cord stops halfway out, the engine kicks back so fiercely it tugs the black plastic Cord Grip clean out of my hand & slams itself hard against the plastic cover. And after all the dramatics, no sign of a start–up. Any ideas ???

    Also a Victa apprentice I know suggested I remove the exhaust box & inspect the piston for scratches.M y Victa has had v. little use, been well housed, how in the world could the piston have been scratched ???

    Would apprec. your diagnosis & suggested treatm’t.



    • Hi Tony

      The most common cause of the symptoms you describe is not having the blades and blade carrier installed or having them installed incorrectly. The blades must be firmly & correctly installed in order for the mower to start correctly, if they are not the timing of the engine is disturbed and it tries to start in reverse yanking the pull cord out of your hand.

      If you Victa has had little use there should be little scratching present, Scratches are caused by a number of factors, Dirt passing through the air filter into the engine, Incorrect Fuel mix & Excessive carbon buildup inside the engine.


  8. Hi,what is a poppet valve spacer,and where do they go? I have an ageing victa and it tends to run very high revs,where on your site can I purchase them? Thank you kindly

  9. Thanks Lachlan ,I have a victa master cut 460,had purchased a diaphragm and new springs,put the carby back correctly,but it will not accelerate or decelerate,just idles ,the poppet valve looks rather past its day,as does the cam ,when I purchased mower not long ago you could only push the accelerator down half way,maybe I would need to purchase a new carby body? Cam and poppet valve,do you sell the G4 body,your help would me much appreciated,love your site and your online shop,you have been a great help,all the very best,Andrew PS is the poppet valve supposed to click into place? As mine just spins around,thanks again

  10. Hi , Lachlan
    I am refurbing the carb on my Victa Keystart ca 1994, I think. I replaced the cap some years ago and found that the original white needle was too long, so I solved it with a bit of careful filing and shaping. Seemed ok for some years, but now needs some tlc. The cap is genuine Victa CR03501A; according to the catalog, the needle is CR03404A. On your website and everywhere else, there seem to be two different needles (long and short, yellow and black) offered as replacements “for all models from 1974 onward” for the same 03404A part.
    How can this be? What is the difference between short and long? I can’t find any answer despite hours of googling. Noting my experience with the original white needle, I suspect length is significant; the lack of info on the web and ambiguity about interchangeability suggests otherwise.
    Sure, I can just get one of each and “suck it and see”, but I prefer to know.
    Can you clarify, please?

    • Hi Roman

      The difference in length is very small about 0.6mm in most cases either needle would work, However the yellow needle tends to suit older primer caps better then the black. The black needle is used for most new caps and the yellow should be used if the black needle is not long enough to allow the needle to seal in the copper seat located in the primer cap. I believe the yellow needle was first made to be more visible then the black to avoid being lost as easily.

  11. Thanks, Lachlan. My original white needle was so long that the float would not swing up far enough to enable the cap to go on. Hence the careful filing I referred to. I probably removed less than a mm, but of course that amplifies to quite a long distance at the extremity of the bowl.
    I’ll order one of each, anyway.
    BTW, I love your videos. They have helped me a lot (I don’t fix a lot of lawnmowers!)

    Thanks again

  12. G’day again mate…..
    I am still trying to fix my Victa Vantage……I got it in 2006 but it hasn’t been used a lot. It’s a bloody good little mower and I don’t want to get rid of it.

    The primer bulb cracked and eventually I got a new primer cap kit….with a yellow needle. I thought that would do the job. Anyway I can see through the white primer cap and it won’t fill up with fuel past the level of about 8-10 mm, even when I press it furiously. Could that mean that the needle is too long and therefore “plugging the hole / sealing the hole/ cutting off fuel intake to bowl…… too early? The reason I think that … because the mower is still in pretty good condition. I pulled the carby apart tonight thinking the diaphragm is no good but it seems ok. The rubber boot / grommet for the 2 x ignition wires is stuffed. I know I can put a manual ignition / on-off switch there but can you tell me …is it imperative to have that hole sealed if it doesn’t have wires or rubber boot sealing it now?

    I can get the mower going if I pump the primer cap for ages …then it will run for a few seconds and cut out.
    Oh…when I put the carby back after dismantling it….the operation of the throttle is sticking and jamming somewhere , especially from “hot start to run” positions. I have taken it off and on a heap of times and looked at your tutorials about re installing the carby….I can’t seem to see what I wrong. ( I have taken out the ignition wires from the carby) I will plug up the hole with something like glue or silicon if you advise.
    What do you think mate….? Do I need a new carby…..different needle……diaphragm kit ? I am wondering how come the throttle operation is jamming up in there a certain positions after I reassemble the carby.
    Grass is about 3 foot high now out the back!
    Great videos too….

    • Hi Mick

      yes It may be that the yellow needle is too long, This would not allow fuel to flow into the bowl properly, You can sand down or cut off the end of the needle to make it a little bit shorter as long as you leave the end that goes into the seat untouched. The black needle is about 0.7mm Shorter then the yellow.

      The rubber electrical boots need to be either replaced or the hole sealed up, Without the hole sealed the carburetor often runs lean due to the increased airflow.

      The throttle cables are quite sensitive, If there is any resistance within the carburetor the wire will often flex rather then push the cam this makes it feel jammed, after the cable has started flexing it is often hard to stop it, If there is no resistance in the carburetor all you can do is check the end of the cable and make sure it is not bent at all. Sometimes a small bend in the cable weakens it and causes the flexing problem.

  13. Thanks heaps for your reply, you answered everything and in good detail! I’ll try those recommendations on the weekend. I gotta tell you…your tutorials are ” on the money” with quality and explanations. I’m sure they’re a real help to a lot of people fixing their mowers.
    Thanks again guys,

  14. Hi again Lachlan or Push Mower Repair admin……

    I sanded down the needle a bit, gently… it and now the carby fills up to 1/2 the level of the white plate, maybe a touch more….( I can see through it to verify that).

    I have had the carby off heaps of times and refitted it, I plugged up the hole where the ignition wires used to go through. They don’t go there anymore because the rubber boots had deteriorated badly so I decided to omit them and just use a manual system. Anyway I have had the mower running a few times but still it only goes for few seconds, until the fuel goes out of the crank I think. I’m wondering if I have made the needle too short, or if the diaphragm is too weak, ( from pulling it off and on heaps of times).

    The little round piece ( about the size of a 20 cent coin) on the back end of the carby facing rearwards……( where a vacuum hose goes) …is it supposed to be really easy to pull / push in and out? It seems really hard to pull out but really easy to push in. What position should it be in at start-up? I’m wondering if that is a culprit too.
    One other thing that I find strange / different to before……..there is always a residue of nice oil deposited under the carby, onto the body of the mower , if I leave the fuel tap on. I have not noticed it before. It is a pool of nice oil which I assume is left after the fuel has evaporated. I have a 25:1 fresh mix.
    Maybe I should think about a new carby…….if that is the case Lachlan what is the price of a replacement carby from your store.
    Appreciate your advice on this Lachlan / Push mower repair ……

    • Hi Mick

      Sounds like the needle problem has now been fixed, Halfway filled is how it is supposed to be.

      The plastic plug in the carburetor cap is a lot harder to get out then it is to get in that is normal, The diaphragm should be okay as long as it’s edge sits nicely around the carburetor so a seal can be formed when the lid is in place.

      Victa’s have a tendency to slowly leak fuel when the tap is left on as it passes into the carburetor and leaks out the joint where the carburetor manifold and the carburetor join, There is no much that can be done to stop that its best to just turn the fuel off after use.

      a full replacement carburetor is $125

      It may be worth checking the following to eliminate problems, Decompressor function, Compression, and the top and bottom crankcase seals.

  15. Hi Push Mower Repair….

    Thanks for that advice. I checked the decompressor and it seemed ok apart from the little valve that seemed to be a bit weak on the “return spring strength”. It doesn’t have the little outside retaining clips like on your video….instead, the 2 pieces are crimped together by the top piece wrapping around the other. I assume that when one takes it apart the integrity of the unit is compromised a bit.

    The crank-case (upper) seal….I think it was a bit stretched and was a very very loose fit in the recess for it.

    I visited my local tip and was able to cannibalise an old Victa Mustang that was already pulled apart. I got the de-compressor, the top crankcase oil seal and a carby complete…for 2$. I gave them 5$. I had to clean the carby a lot , cos it had 5-8mm of built up gunk all through it but the diaphragm was noticeably stronger than my other one. It made a better seal I think. I sealed up the hole for the ignition wires with epoxy liquid steel. The throttle is a bit funny at the bottom of the controls (“Hot Start / Run”) and there is a distinct “clunk” …..I have noticed that if that “clunk” doesn’t happen the mower won’t start and so you just pull throttle control back to “Stop” and then down to “Hot-Start / Run” again. I know it says to do that on the control box but I have never really paid much attention to that and it seemed to go ok.
    Anyway, the mower runs really well…..I am happy with it now. Next I will put a simple “On / Off” toggle switch on it.
    Cheers heaps for your help….I learnt a lot getting it up and running.


  16. Lachlan, Mick
    Sounds like a common problem. I just recently rebuilt my Victa (thanks Lachlan for the parts and advice) and it started first time but speed hunted badly and would not keep going. Fuel starvation. Turns out that the carb needle was too long (I had the black – supposedly short- one) and the float sat on the bottom of the carby bowl with no scope at all to move up. I ended up taking about 0.9mm off the bottom of the needle to just get 2-3 mm float movement. Just mowed my lawn now for the first time since rebuild, and all was sweet.
    I have just read Mick’s post and Lachlan’s reply that the carby is supposed to be about half full. I will check this next time I mow. Maybe the needle is STILL too long.
    As I started, sounds like a common problem; a couple of earlier posts in this thread suggest the same issue.
    Lachlan, may be worth adding a bit to your video to confirm the amount of float movement there should be.
    Also , Lachlan,, you say in your recent reply to Mick that “Victas have a tendency to leak fuel….”.
    This can only happen in the way you describe if the needle doesn’t shut properly on its seat. Is that the case?

    • Hi Roman

      If the mower performed fine I would assume the needle length is no longer a problem, Yes when sitting over long periods fuel can get between the needle and the seat and slowly fill the carburetor, We have seen this occur over a period of weeks or just a few days depending on the condition of the needles and seats. As such we recommend turning the fuel off after mowing to eliminate any possible leaks whilst the mower is sitting unused.

  17. I have an old Vivta Mustang 18 V40 GTS that I am having trouble with with petrol leaking out of the Priming Bulb, Sholuld this be in a Horozontal position .
    The mower goes well and Would like to keep it but I need it to be relaible
    Does the brass screw Ie I presume the jet by screwing in or out alter the speed of the mower or do you screw it in hard to seal the o ring ..
    Thanks Don.

    • Hi Don

      Leaking out of the primer bulb is usually cased by a float or needle problem that causes the fuel level to be too high inside the carburetor. You should check there is no burrs on the float arms or needle and that it can move up and down freely.

      The brass jet is tighten firmly it does not adjust the speed of the mower. However you should be careful when tightening as you do not want to damage the plastic threads.

  18. Hi Lachlan
    I noticed that the poppet valve has an on its base an A, 2, C and a also a raised stem (located between the 2 and C).

    What is their significance and correct positioning?

    • Hi Frank

      The default setting is on C, The A setting slightly reduces the idle speed. I do not know the effect of the 2 setting

  19. Hi
    I had the same problem with my G4 carby and I followed your good advices through this thread. Replacing the needle, buble plate’s O ring, diaphragm, setting the poppet valve the recommended A position, but no brass spacer(s). It started for the second pull of the cord, but the idle speed in the Run/Cold start position is high. If I push the throttle down to Hot Start position it slows down and stops.
    There is another problem too. I tried to use the mower with the high idle speed in the Run/Cold start position, but if the surface (the land) is not flat (horizontal), but sloppy to the right as you push the mower, it will stop.
    Can you please recommend some solution?

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