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Posted By : Sarah Haley, 13-Feb-2006, 02:43pm
Can anyone give me, as a bit of a mechanical duffer, some advice on the SU carbs on my 1500 Spitty? The problem is that the idle speed is far too fast once
the engine is up to a decent running temperature, and the hotter it gets, the faster the idle becomes. The cooling system should be working OK, as it's
just been flushed, refilled, thermostat replaced and the radiator core seems OK, as do the hoses. Initially I suspected the throttle/choke cables (it felt,
from the driver's seat as though the choke had remained on), but a poke around under the bonnet suggests that the cables aren't at fault. I imagine it's
the carbs that are to blame, but I'm not sure.
Be gentle with me, I know nothing!
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Posted By : Chris Taylor, 13-Feb-2006,
04:31pm
Could be a number of things.
I'd double check that the fast idle set up on the carbs is as per the workshop manual, and that the throttles can fully close down onto the idle
stops.
It is possible that the mixture is badly out of adjustment, so retuning is required. (The way the engine runs in general might give some
indicators).
It is also possible that the throttle spindles are so worn (do they wobble in tghe carb body if you grip each end of them?) and allowing air to leak
in? (Reconditioned carbs needed if so).
Not knowing how hot things are in your description (although at this time of the year not likely to be exactly roasting!) it might be the case that the
infamous "waxstat" jets in the carb are getting a bit warm and upsetting the mixture.