General Advice On Carburettor
Rebuilding.
By Bjorn ol-of Berglund
On every carburettor rebuilding there are a few basic
details that should be remembered, irrespective of what kind of carburettor
that will be rebuilt.
Always find out the spare part asset. It’s no fun at
all in the middle of the rebuilding to realise that the gasket that you’ll need
is nowhere to find. Make sure that you’ll have all the parts that you’ll need
before the dismantling. Of course there can come up some surprises when you
have started, but the minimum will be a gasket set.
You should also do some documentation, preferable with
a digital camera. It does not seem to be that difficult when you start to
dismantle it, but if you for some reason get delayed with the assembling, you
will realise how bad your memory actual is. A workshop manual covering your
specific carburettor is a good source for knowledge.
The carb that we are going to rebuild is a Zenith
42WIA 2, the very same that was original mounted on the MK3 Zodiac. It is in a
decent shape, with a little play in the throttle spindle, which has to be taken
care of.
When you remove the throttle spindle from the housing
you should be aware that the screws that keep the throttle to the spindle are
notched. That is to keep them from coming loose and fall into a cylinder.
The hole in the trottlebody has been oversized with a reamer,
and a bushing has been carefully pressed in place.
Then the axle diameter has then been turned down with
a lathe to match the bushing size. Still to do is shortening the bushing.
The needle valve is also account for as a wear part,
and is therefore replaced.
It is important to keep track on every screws when you
disassemble the carb, so a suggestion would be to group them in small plastic
bags. For example the upper body screws together, do not forget to take detail
pictures during the work.
When the whole carburettor is taken apart, or at least
as much as possible, the time for cleaning has come. If you do not happen to
have access to an ultrasound cleaner, you’ll have to use what you can get hold
on. Old toothbrushes are excellent to use. Compressed air is also a necessity,
there are a lot of narrow channels and holes in a carburettor that have to be
blown clean. To try to clean them with a wire, a drill or something else will
only end up in a destroyed carb.
The solvent to use is ordinary degreaser or some kind
of “carbcleaner”, along with a small brush it will
remove most of the dirt build-up. If the carburettor body is oxidized it has to
be glass blasted, but that requires that all channels and jets are properly
covered. If any glass should get into any channel, it will be really hard to
get clean again. After glass blasting an ultra-sound cleaning will be
necessary.
All linkage arms are glass-blasted and inspected for
wear. If any bindings occur in axels or linkages, should it be checked out.
Now for the fun part, rebuilding. As always a careful
and cleanliness assembling will ensure for a good result. Remember to apply a
light coating of grease on all moving parts. Sometimes renovation kits contain
an exploded view of the carb that are covering more than one version of the
carburettor. It is also during the assembling stage the initial settings are
done. For example the” float level.
If you forgot to
note the mixture screw settings during the dismantling, a workshop manual will
be handy.
Additional Info by Steve Pope (59-Z-MK2)
I had just finished rebuilding a pair of Mk2 Zenith 36 WIA carbies for my project when this article came in. I acquired two full
rebuild kits via EBay UK for a 1/3 f the cost I could acquire them from
anywhere else. These kits contained all the gaskets, jets, mixture screw,
seals, diaphragm, float valve etc. Kits are available still if you search and
cost around $100 each from Classic
Carbs here in Australia. The job is easy if you
do the Carbies in the 3 sections 1 at a time from
start to finish, that way you don’t have 100 bits and pieces lying on the bench
Note: It might
be advisable to use a little loctite on the throttle and
choke butterfly screws for peace of mind because like Bjorn said you don’t want
them ending up on top of the pistons.
Disclaimer:
The advice and guidelines given in these articles are given in good faith.
The owners and managers of the Galeforce Zephyr site will take no
responsibility for any injuries or loss sustained while carrying out the
described tasks and procedures or any consequences arising. Please read
the Safety First
Article
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