William Eastman wrote:
> Clearing the carbs, also called clearing the plugs, means to rev the engine
> up after it has been idling for a while. High performance engines in
> particular don't like to idle for long periods of time. The idle gets
> lumpier and lumpier until the engine dies. I don't think that the carbs
> are actually getting backed up. My guess would be that the rich, cool
> mixture slightly fouls the plugs and increasing the rpm heats them up and
> clears them, hence the second, less common name. Most LBC manuals
> recommend reving the engine occasionally while setting the idle or to
> "clear the carbs (plugs)."
The actual reason for this is that during idle, the low airflow
doesn't do a very good job at keeping the fuel vapour suspended
in the air. So fuel collects along the pipes of the intake
manifold. If left there, it tears off in sheets at random
and goes through the engine...
When tuning of course, these random bursts of fuel ruin any
type of fine measurement you are trying to make at the carbs,
so you have to clean them out, usually by revving at 2500rpm
for 30 seconds or whatever the manual says. Then you can start
tuning again.
--
Trevor Boicey
Ottawa, Canada
tboicey@brit.ca
http://www.brit.ca/~tboicey/
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