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Collection, Preservation and Display of Old Lawn Mowers

slow running tube zenith 13 tca2 question

What's the best method of extracting a stuck slow running tube from a zenith 13 tca 2 without damaging it?

I have heated the body with an electric paint stripping gun and applied plus-gas and attempted pulling with pliers but being brass a I dare not apply to much pressure in case I squash it.

I did remove one successfully before, but I used a blow torch and succeeded in melting the body a little bit. The carb worked though, although being very worn mechanically it did not idle very well.

I don't want to risk doing that again.

wristpin Thu, 15/12/2016

They can be difficult but I would say that you are on the right track with the hot air gun although before I owned such a thing I found that putting the whole carb bowl in a pan of water on the stove and giving it a good rolling boil for about five minutes got a good uniform heat into it.

The calibrated bit is at the opposite end so you can afford to be a bit brutal with the bit that's sticking up. Good square ended pliers end on and wiggle a bit or failing that and with care, side cutters as close to the bowl body as poss but with a small diameter nail or twist drill laid across the top as a fulcrum and then lever down on the handles .

If you do squash it a bit they can be recovered with the careful application of the tip if a scriber to restore the shape and replacements are still available.

The fuel for the slow running mix is drawn up that tube (more correctly pushed up by atmospheric pressure) into a gallery below the idle adjustment screw from where, when mixed with air, it enters the inlet manifold through a tiny hole (no 6 on the second Dropbox link) which is only visible / accessible looking into the manifold from the engine end  - and then with a good light. On a couple of occasions I have found that hole blocked and had to probe it with a bit of fine wire to clear it.…


goodgrass Fri, 16/12/2016


It's out - intact. I inserted a welding cleaning tip which fitted the tube exactly preventing it from collapsing when extracting. I used a bit of a slight twisting motion to free it.

The needle seat was also a pig to get out, somebody had been riving on with that and damaged the slot.

wristpin Fri, 16/12/2016

That's a great idea and like many such ideas - so simple!

On the subject of your needle seat , brass carburettor jets and emulsion tubes with a single screwdriver slot are prone to suffering from similar abuse but the best approach is a decent hollow ground screwdriver which, unlike a conventional slightly tapered one, will reduce the tendency to cam out of the slot.

Equally, if the seat or jet has a hexagon rather than a slot the best approach is with a single hex socket rather than the more usual bi-hex or multi hex socket.


goodgrass Mon, 19/12/2016

thanks for sharing the photos.

I will have a look for one of those, although in my case the damage was already done by somebody else.

I had to resort to heat mole-grips and plus gas  as it was well and truly jammed with varnish

wristpin Tue, 20/12/2016

Jet screw drivers.

Originally I made my own from a bit of silver steel rod but over the years collected a couple of others.

The green one is a German made Weralit which was, I think, an Aspera " special tool" and the two red ones are of American Millers Falls  manufacture bought as Briggs and Stratton service tools.