Lawnmower carburettor aargh!

Mother's lawnmower hasn't been used for about a year. She has had a hip operation so I cut the grass for her until she feels able/wants to. Her lawnmower is a Victa 3 two stroke. Now last time it was used, it worked. I know that it's the carburettor so I started by cleaning out the tank and removing the old petrol. Put in new petrol and it doesn't start. So I take apart the carby and clean it, unblock fuel lines with air compressor and it put it back together, still doesn't work with the added complication of the Priming pump gushing petrol everywhere. Petrol is getting into the carby from the tank but I don't think it's getting into the combustion chamber from there. I have been lugging my lawnmower over to her place but back is playing up so I'd like to see if I can fix hers.

Dazzler or any other experts, what should I do next bearing in mind I'm no expert on these things but was surprised at how few parts there were in this carby. Sure I can do this with a little bit of guidance.

Hi Tiger

Sounds like either the needle is not seating, the float is not in right or the rubber oring that seals the big black flat outside piece to the main body is missing or crushed.

Give this a try;

Take it off again and pull completely apart.

Im going through this blind so bare with me.

Tip the large body of the carby on its side so the small outlet that normally connects to the engine body (steel area) is down.

You should now be able to see down into the insides of the carby.

Find the float (big white thing with two little hangers that allow it to pivot from one corner.

Find the needle. It is normally red and about the size of two matchstick heads. It goes into the hole on the opposite side where the fuel comes in. Put the needle in the hole and the float on his hangers. Push lightly up with your finger and watch that the needle goes up. Lightly blow from the other side and it should not let any air through. Let it down and see if air comes through. If this is okay move on otherwise get a new needle and float.

Still on its side the needle and float are on, now put the bigger of the two grey coloured plastic bits in making sure the three little tangs/arms are in the slots on the side of the carby body and the concave sections are facing you. Now drop the other grey piece in so that it fits in the concave section.

Getting hazy now. I think you need to attach the throttle cable with the ball bit on the end into the grey thing (air/fuel adjuster) and this is done by holding the black throttle cable at about 30deg angle to the body and kind of clicking it into place.

Now get the round rubber diaphragm and the long pointy thing that looks like a chess pawn with its head hacked off and put it through from the bottom of the carby (small hole) and hold it in with your index finger of non master hand.

Push the rubber diaphagm over the pointy bit and then slide the metal clip the size of a 20c piece over the pointy bit and secure.

You should now have left a spring and the end cap of carby. The spring fits in a recess in the cap and against the steel bit on the diaphragm. Push the cap home.

Now VERY carefully cut the blue wire.....no the red wire :D.....no, dont cut any wires :wink:

Now I may have confused the models and you have one that has the float etc in the cap. If so its very similar. If you have no luck take some photos of the bits and I should talk you through it better.

good luck

dazzler

Hi Dazzler and thanks for your assistance on this.

I've taken some photos to show you what I have. Photos 1,2 and 5 are of the carb body. Photos 3 and 4 are of the float and needle parts. On this model the float and needle are in contained in a float chamber. When I had a close look at the float I noticed that there was no needle, this may have dropped out when I took it apart the other day. So I tried again today to fire the mower up and it didn't work. I have a Victa 2 stroke that does work and the carby is pretty much identical to my mum's mower, mine did have a needle but it's yellow. So I swapped the cap, float, jet and needle onto my mum's machine. Prime it and it starts leaking a bit of petrol under the cap, but it still won't start! Then I check the spark plug and it's flooded.
I guess we can conclude that the cap and float is not the problem as it works fine on my machine but there was a fair amount of leakage when I swapped them over and maybe it's not a perfect fit but they look the same. Does this mean that the problem is further on with the valve or the diaphragm. Both look fine, can 't see any perishing of any sort.
What now?:? By the way, there are 2 electrical wires that are connected to the carby, how do I disconnect these so I can take the whole carby assembly away from the machine?

Hi

this one is slightly different to my explanation. Firstly the wires shut off the engine when the cable is pulled to off. To remove there should be a small black rubber cover with one going straight in and the other at 90deg. The 90deg one fits in two small holes in the carb body and the rubber seal. Pull it out (may need to wiggle) and then the other one pulls out.

From the pics it looks like the model that has a round white plastic side which the float and needle sit in. Seeing as it is flooding it would be the needle / seat not quite right. I would go along to the victa man and get a replacement assembly which will have the side plate, o ring, needle and seat. They are pretty inexpensive and will solve the flooding problem and the sealing problem. Double check that the little oring is fitted correctly to stop any leaks. A little rubber grease or normal grease will help seal it.

In the meantime here is a tip. Turn the fuel off, drain the carby by opening it, take out the plug. Put a tiny (few drops) of oil down the spark hole and pull start twenty times to get the oil on the cylinder. Often when a motor has been flooded and is old any oil helping seal the rings/cylinder is washed away and you lose compression.

Remove the wires from the carby and isolate them. Wait half an hour and put the spark plug on the spark lead and ground its side to metal (motor is fine). Pull and see if it has spark. If it has spark put plug back in and turn the fuel on just a little (pull hose off carby to see that a little is running out.)

Full throttle and start pulling. It should start before it floods and it should run.

But base line would be replace those carb parts.

good luck

And when its all back together if it still won't start , change the plug and get a can of aerostart from supercheep , spray liberally into the air filter and try again :2tsup:

Quote:

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Originally Posted by Ashore

And when its all back together if it still won't start , change the plug and get a can of aerostart from supercheep , spray liberally into the air filter and try again :2tsup:

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You butcher :p

Don't be mean get her a new cheapy and save the hassles:D
Pete

Dazzler you are a GENIUS!!!! Did what you said and it started and ran. Only problem was that it didn't turn off immediately when I turned the petrol off, nor when I turned off the throttle cable. Does this mean that the cable is not set right? Also there was a lot of blue smoke. Can we now conclude that the problem is the float assembly and a new one will fix everything?

Anyway, greenie sent and thank you very much, my back appreciates it :U.

She will take a while to stop after the fuel tap is turned off as the fuel has to be used up from the fuel bowl and as the wires are disconnected it wont short the electrics as normal to shut off.

A new float, needle and cover and oring should fix it. And the blue smoke is from the oil so no big prob!

cheers

dazzler

Thanks, Dazzler. Only thing is I didn't disconnect the wires. Am curious though as to why did it start? Obviously turning the fuel tap released some petrol but why the full throttle, what effect does that have?

If an engine is flooded full throttle allows more oxygen in so it leans it back enough to start sometimes.

If the wires are connected properly they should have stopped the motor when the throttle was shut off. To check they are fitted properly go to full throttle (engine off) and lightly feel the wires. As you close the throttle to off you should feel them move slightly as they are forced into contact by the grey part (sliding venturi) inside the carb. If not there may be an adjustment issue.

But, you are better off running it out of fuel so that the carb is empty and there is no chance of the fuel going off. I usually turn the fuel off on my last run on the lawn and it stops shortly after.

cheers

Thanks for that info Dazzler. Flushed with success on the Victa, I do have another lawn mower which is a 4 stroke Rover with a similar carby issue. Bought if from a garage sale as a backup for the Victa and it stands tucked away in the shed. Now you've guessed it, it doesn't start, it worked once. I've always been wary of dabbling with a 4 stroke, 2 stroke I can handle because of its greater simplicity. There's no fuel tap that I can see on it, are these much harder to fix and have you any advice on these (ie 4 stroke mowers)?

By the way Ashore, I did use Start Ya Bastard on the Victa but it failed to do anything.

Here is a photo of the Rover.

Quote:

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Originally Posted by Tiger

By the way Ashore, I did use Start Ya Bastard on the Victa but it failed to do anything.

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From your description it was proberly the fuel and the fact it flooded, Dazzlers fix was the right way to go but sometimes if you drain the fuel , clear any blocked fuel lines drain the carby remove the plug and turn it over a few times without the plug in , add as daz said a couple of drops of oil turn it over again slowly to coat the liner and rings make sure the plug is good , clean and the gap right and is getting a spark , spray aerostart into the cylinder , 4-5 seconds worth replace the plug more aerostart into the air filter breather 10 seconds worth go to 1/2 choke and go for it , Butcher I know but it works :B

If you have this issue on a 4 stroke check your sump as your oil will have been greatly diluted by fuel, usually when a needle/float isn't sealing off then you'll have to change the oil out.

For the rover, I don't know anything about the brand, we don't have it over here, but for general 4 stroke troubleshooting I usually just replace the basics, air filter, spark plug, if it has an inline filter that goes too, dump out all the fuel from the tank, look and see if there is water in what you dumped out, it will be pooled at the bottom, put fresh gas in, give it a try. If it doesn't work then you have three basics you need for it to run, fuel, spark, and air. If you replaced the filter, you know it has air, a trivial thing but its very common for a pugged air filter to make them run pig rich and hard to start, and the air filters on these things get absolutely filthy in no time at all. Spark is easy to check, if you don't have a tester, either in line or mechanical type, then just pull the plug out, leave it hooked to the wire, place it near the head so it can jump to the metal and pull the cord a few times and see if you're getting a good spark. If not, then you can usually pull the flywheel off and clean the mags with some sandpaper, they get rusty sometimes. If that doesn't work, then its the little coil thingie. Check that its not just a bad connection on the safety switch first though, thats more common than the other two.

If you're getting spark though, then you probably just have a clogged up carb. Get a spray can of carb cleaner, a little tiny wire (florist flower wrapping wire works well) and strip the carb down. There will be lots of little tiny holes, some of which you almost need a magnifying glass to see, use your wire on these to make sure they are clear. You should have one or two on the needed that screws up from the bowl if you have that type of carb, there will be a few other misc holes and orifices throughout the carb as well, give everything a liberal spraying of carb cleaner and scrub anything that looks gunky. I like to adjust the needle and float at this time and you can er suck on the inlet tube to make sure it is sealing, some people dont' care to do this but it saves you from having to go back in.