A jointing (sealing) compound for mower carb?

[Ross365]

Having trouble with a mower carb. There are only two screws hold the two halves together, I think it might be good to use a jointing compound (petrol resistant) on the thin gasket. Blue Hylomar is my usual go to, but wonder what else anyone would choose in preference? Hylomar might be a bit 'stodgy' for this.

There's an emulsion jet between the two halves of the body; if that it not perfectly sealed, it could be the cause of my problems.

 

[tigdlo]

Is the bowl face flat? Shouldn't be any need for sealant, flat sealing faces and a proper gasket is all that should be needed.

I've had sucess flattening Zenith carb bowls on a surface plate with 240grit wet and dry, the high spots were around the screw holes.

 

[Seadog]

Distortion through overtightening is normally why they leak. I used to see it time after time with the AMAL Monobloc float chamber cover.

 

[The_Yellow_Ardvark]

Blue hlyomere.
Spelling is wrong,

 

[Seadog]

Hylomar

 

[The_Yellow_Ardvark]

Hylomar

That as well.
The voice command does not like the A303.

 

[Ross365]

I am clutching at straws. My beloved Suffolk Punch served faithfully for 30 years and then one day stopped running. Long story short, I stripped the engine down and found it all looked very good except the exhaust valve clearance was way below what it should be and I dealt with that and out it back together. When all complete, it started on the first pull and I left it running for quite a few minutes, with no problem, and so I stopped it. That was weeks ago and that was the last time I got it to start.

Now, it's good if it runs for 10 seconds. The carb has been ultrasonically cleaned and loving re-assembled. It's currently got Aspen fuel in it. I don't think it's a spark problem (or it wouldn't start at all), but maybe it needs some of this hlyomere stuff?

 

[8ob]

I use a smear of grease on paper gaskets, shouldn't need any more than that unless the faces are distorted.

Bob

 

[voipio]

Emulsion tube holes clogged??

 

[ajlelectronics]

The clue may well be in that your exhast valve clearance had reduced. That is valve seat recession and you may well have a burnt valve seat which is making it difficult to start, due to lack of compression. It isn't really going to be down to the carburettor in my view, but Hylomar would be the stuff if you have to use anything. Like Bob, I use a thin smear of grease to seal a secondhand gasket, if I am forced into it.

 

[Ross365]

Yes, on my most recent re-build of the carb, I used a smear of silicone grease on the gasket.

Re the emulsion tube, that is stuck rigidly in the body; getting that out without damage looks risky. So, I tested it by filling a syringe with alcohol and placing the needle in the top of the tube. When I squeezed the syringe, lots of alcohol went through and came out of the pickup hole at the bottom. I suppose I could try heating the body to get it out, but it seems to be OK.

Re the valve, I had the head off and re-ground both valves and seats. Judging by the effort needed to pull the starter, there is good compression.

After the rebuild, what allowed it to run perfectly for some minutes until I stopped it, and it now it won't run? Think that has to be fuel or spark? Very odd though .

 

[8ob]

After the rebuild, what allowed it to run perfectly for some minutes until I stopped it, and it now it won't run? Think that has to be fuel or spark? Very odd though .

Easy start is your best friend on problems like these, a quick squirt of that and if its a carb problem it will fire up and stop. if it doesn't look elsewhere like ignition.

Bob

 

[julianthegypsy]

It's likely that although you had valve and seat reground, there's still not enough valve clearance, so it's fine when it's cold but too tight as soon as it heats up so it leaks. Get a feeler gauge between the valve and cam and if necessary just grind a bit of the end of the valve.

 

[Alan Reynolds]

It could be the plug. We have plugs on go karts that spark perfectly out of the engine but cause problems under compression. And you now have more of that now you ground the valve seats. Easy Start of a few drops of neat fuel in the plug hole should start the engine for a few seconds and help eliminate where the fault lies. Any pictures of carb and mower?

 

[voipio]

Re the emulsion tube, that is stuck rigidly in the body; getting that out without damage looks risky. So, I tested it by filling a syringe with alcohol and placing the needle in the top of the tube. When I squeezed the syringe, lots of alcohol went through and came out of the pickup hole at the bottom. I suppose I could try heating the body to get it out, but it seems to be OK.

The emulsion tube has lots of fine holes along the sides of the tube. If they're blocked, the emulsioning action doesn't happen, and the engine conks out on tickover.

 

[Ross365]

The emulsion tube has lots of fine holes along the sides of the tube. If they're blocked, the emulsioning action doesn't happen, and the engine conks out on tickover.

We may have our wires crossed. The carb I'm dealing with is the Zenith 13TCA-2. It does not have an emulsion tube - just a slow running tube as below. I cannot get that tube out. It does not look to have the holes in the side as do the emulsion tubes in other Zenith carbs.


See https://www.japgmowers.co.uk/carb-s...t-020582-q00500-q00699-f016s00500-15223-p.asp