Re: fast idle on 2000 roadster

[Simon Favre <simon@domain.elided>]

Mark, 
There are a couple of things to check on this. Make sure the timing is
correct, because timing that's too advanced will produce exactly those
symptoms.

The other thing that comes to mind is carb balance. The idle speed screw
only operates on one carb. The other is slaved to that one. If the slave
is still open when you adjust the other one closed, the car may idle
fast and unevenly. The best way to check this in the car is using the
inspection covers on top of the idle progression holes. The newer Webers
do not have these removable covers, which is a great pity. If you look
at the idle screws, between each idle screw and the nearby accelerator
pump jet cover, there should be a brass plug with a screw slot. If what
you have looks like a miniature freeze plug, the rest of this will not
help. This check is done with the motor off. You remove one inspection
cover from each carb. Screw in the idle speed screw until you can see
the butterfly valve thru one of the progression holes in the carb with
the idle speed screw. Adjust the balance screw until the slave carb has
its butterfly valve in exactly the same position under the progression
holes. Close up the holes, readjust the idle speed screw to where it was
and then fire it up for further tuning. Always do the final idle mixture
adjustments after the car is fully warmed up.

If you can drive the car after this, an air leak in the manifold should
make one plug come out a lot lighter than the others. An idle drop test
may make it more obvious which cylinder is causing the fast idle, if it
persists. An idle drop test consists of pulling one spark plug wire at a
time while the motor idles. You need specially insulated pliers, or an
engine diagnostic instrument to do this test without getting shocked.

If your carbs are old, they may need rebuilding. The bearings on the
throttle shaft can leak air if they are worn. You can usually find this
out by shooting them with WD-40. The liquid will seal them up temporarily.
If the idle drops, then comes back up after shooting the shafts, you have
worn bearings in your Webers.

Good luck with it.

Simon

Mark Dubovick wrote:

>I've got a cast iron 2000 ('61) which has been changed from solex to
>webr 40 DCOE carbs. After fitting the jets from a Euro 2000 setup the
>car idles at 2000rpm. I haven't done a whole lot of troubleshooting.
>Turning the idles screws to minimum does nothing. The throttle shaft is
>at minimum throttle position. Does anyone have any ideas? My guess is a
>intake leak by the carb shock mounts or somewhere in the intake manifold
>area. Any help is appreciated.

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