William Eastman wrote:
>
> Bruce,
>
> 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)."
>
> As far as tuning a pair of SU's, I think that the most important first
> step is to get the two carburators set the same. This is where standard
> tuning procedures work great. The old "lift the dashpot" aproach will
> probably give fairly consistent results for a good starting point.
> Personally, I took my dashpots off and measured the position of the needles
> and seats and set them at the same point for both carbs using a dial
> calipers. I then lifted the dashpots to get them as close as I could.
> After that, I am still fine tuning but I always adjust them both the same
> amount. I just leaned them a flat two weeks ago because its warmer
> outside. I am considering leaning them another flat now to improve the
> idle. Read the plugs to judge the overall state of tune since you do not
> want to go lean under power.
>
> Regards,
> Bill Eastman
> 61 MGA
About two years ago (7 - 8k miles) I re-synched the carbs on the
roadster from first principles, it took an hour or more. Last year I
didn't touch the carbs at all, except possibly idle speeed (both screws
the same amount). This year I replaced plugs and points, reset the
timing, took a deep breath and checked the carbs. Not only was the sync
nigh-on perfect but the mixture was too. Just had to back off the idle
a tad. Aren't SUs supposed to go off tune?
PaulH.
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