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Re: Weber VS SU Question

To: spridgets@Autox.Team.Net
Subject: Re: Weber VS SU Question
Date: Tue, 01 Feb 2005 22:18:37 GMT
Kirk...

Assuming your 1275 is stock.....the old Weber 45DCOE side-draft Sprite
set-up came calibrated for the stock motor and in my case, worked
trouble free right out of the box.

I am advised the Japanese kits will come the same way, except the
Japanese version will have provision for external adjustment of float
level and accelerator pump fuel delivery quantity.

The toughest part of of tuning a Weber is usually "progression" .... that
area between off-idle and the main system coming in.

However, in the already calibrated kits available, this has already
been attended to for the STOCK engine. If you start making major
changes in cam profile, then you'll have to recalibrate the carb. for
such changes but, that's another story.

Most people get into trouble when they try to "save" money by picking
up a "used" 45DOE from another engine, buy a suitable intake manifold
and slap the carb on their Sprite without the benefit of "correct"
calibrated parts (jets, emulsion tubes, idle jets and the like) along
with lack of "open throat" or "fixed venturi" (and maybe specifically,
Weber) edcuation.

So, buy the Haynes manual on Webers so you can read up and
"understand" it's design and "why" and "how come" and how it differs
from the SU "variable choke" design.

There are also two booklets (soft cover) out by Passini. The
"orange"one covers theory and the "green" one is "practical/
operational". But stick with the kits and you won't "need"
these....good reading though if you're interested! :)

The Weber is the Sopwith Camel of carburators. It is designed to be
fine tuned to the application...extremely sensitive to itty-bitty
inputs. Get ham-handed with it and it won't exactly kill you like a
Camel will (and did....the Camel killed as many WW1 pilots in
accidents as were shot down while flying it in combat...I bet you
didn't know this, Kirk....and could care less) but it will frustrate
the hell outta you trying to get the motor to run "properly".

Like the Camel, the Weber is a pussycat in the hands of one who is
educated and favors an educated, assertive touch.....

....as opposed to....  the ham handed, aggressive "you better respond
right to this jet change you SOB or I'll beat the livin' sh-t outta
you with a BFH" approach.

However...  Stay with the calibrated kits specific to the application
and as long as the engine is reasonably healthy, you should have as
many problems as I did when installing one on my stock 1275....which
is to say...NONE.

What will the DCOE do for you as compared
to the stock twin 1.25 induction set-up?

Upgraded breathing comes as part of 
the package, to begin with.

First of all, most 45DCOE's come with air-horns. To fit the Spridget
engine compartment, you want one with air horns on the short side, so
you can fit a decent air filter which in and of itself, will provide
freer breathing than the "tubed" stock cans. Course, this depends upon
the length of intake manifold the carb kit comes with.

For even more free breathing, you want a K & N filter for the filter
can. These usually come properly oiled from the factory and are
included in APT (www.aptfast.com) Weber filter assemblies. These are
premium filters which will last many, many moons with little
maintenance (thus...$$$$$!!:).

What else. Providing the engine is healthy and drawing good
vacuum...faster initial response off the line. Slightly less torque in
the low and low/midrange but more in mid-range to high/midrange and at
the very top. Now these are not "huge" changes in torque/power. They
are minor ones. The biggest most noticeable change I found was more
"immediate" initial throttle response, "off-idle". The engine "reacts"
more quickly to the foot.

One other thing....no more having to synch.  carbs of course. Or
screwing around setting mixture. Set the volume (idle) screws on the
45DCOE according to the Haynes Manual using a tachometer and your
done..basically forever and ever unless you make "engine" changes
(cam, higher static compression ratio, sustantially different ignition
advance curve, etc.).

Webers have teenie-tiny channels within.  A spec of sand can block
these and 'cause all sorts of rough running problems. Use K&N "Sealing
Grease" between filter and filter can. Use a fuel filter between the
tank and fuel pump....another between the pump and carb.

Well...that's all I can think of right now.

You owe me big-time, Kirk.  I missed Judge Judy writing this. 

But it'll re-play at 10PM tonight after O'Reilly & Hannity and
Colmes....  so you lucked out! Enjoy!! :):)

Cap'n Bob
Finally de-frosted
(and running:) '60 Frog





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