Vince--Since the problem started after a period when the carb seemed to
work, I would look for a plugging or air leak problem. The throttle
shaft/butterfly warpage possibility is real but less likely. Try these
tips.
Directly behind the idle mixture screw adjuster is a brass slotted head
screw. that seals the progression holes. check to see that the holes are
clean and that the screw head seals to the carb body. If the idle is ok
but the engine stutters when you just crack the throttle, it is likely that
the progression holes are plugged, or leaking air. It is entirely possible
that the throttle shaft/butterfly are warped but not likely. When you get
your book, check out the idle to progression phase diagram. another
possibility is a plugged idle jet which would starve the progression circuit
by not allowing sufficient fuel to enter both from the idle mixture orifice
and the progression holes. If the carb sat for some time and yukked up the
internal channels, a complete disassembly and chem-tool boil out is in
order.
One way to check this is to use a strong flashlight and mirror and to watch
for fuel coming out of the progression holes as you crack the throttle just
past idle. They should come in as the throttle plate rotates just past the
holes.
Oh yes, read the book and study the circuit diagrams. Webers can drive
one nuts.
-----Original Message-----
From: Vince De Palma <greenery@gte.net>
To: Friends of Triumph <fot@autox.team.net>
Date: Monday, July 19, 1999 7:53 PM
Subject: Spitfire With Weber Problem
>Amici,
>I've got a technical problem for you.
>
>I have a racing 1147 Spitfire with a single Weber 40 DCOE carburetor. It
>works great except at 1000-2000 rpm where is sputters and stumbles. This
>causes no end of problems when I try to start from a stop. I've already
>burned up a clutch. I've been through the carb about a dozen times and
>it's clean and all there. The engine is fine, good compression, spark
>advance correct, dwell ok, valves properly set, no manifold or carb leaks.
>
>So what's wrong? The carb was purchased used a few years ago and worked
>fine for a while, then started acting up with no apparent cause. It may
>need tuning, so I've ordered a Weber book which will be here in a week or
>two. Meanwhile I'll let you experts help.
>
>Any ideas??
>
>vince de palma
>greenery@gte.net
>
>
|