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Re: It RUNS!!, But.....

Subject: Re: It RUNS!!, But.....
From: (Ross MacPherson)
Date: Thu, 25 Apr 1996 01:02:18 -0700
>Last sunday we tried to set the carbs (SU AUD135) for my early '67 B.
>The carbs are rebuilt, I mean cleaned, new jets installed, needles
>(FX), float bowl jets and needles, etc. The engine is OK. We had
>adjusted the valves, set the timing (10 before TDC). The starter
>motor worked OK, engine ran fine (oil pressure 45 psi at idle when
>hot; 60 psi at 3000 rpm). I had Roger Garnetts article about SU
>tuning handy and a Haynes as well, and we have adjusted the carbs by
>the book. First synchronized them, with a handy tool from Gunson, and
>then adjusted the mixture.
>But the engine kept running very rich, even if the jet adjusting nuts
>were turned completely in (at that moment the engine ran rich, not
>very rich!) 
>Does anybody know what's the problem?
>Thanks in advance,
   Greetings Bert!
Sorry, I may be way behind on this. I got behind in my email and am in the
process of sifting through some 600+ messages.  If this has been covered and
/or solved please disregard....
Check your float levels.  If the float levers are at spec (probably about
7/16" at a guess) check for leaks in the floats themselves.     If the
floats have even the tiniest of leaks they will take on gasoline and start
to sink.  This allows the fuel level in the bowl to rise and so raises the
fuel level in the jet, resulting in a richer mixture: more leak = more sink
= more rich.  Remove and inspect the floats.  Give them a shake and listen
for a sloshing noise.  If you hear nothing your problem is elsewhere.  If
you DO hear a sloshing it will be impossible to set your mixture correctly
and the problem will steadily get worse.  The problem is easily rectified by
replacing or repairing your floats.  If you have plastic floats ( I think
all B's have plastic ?) I can offer guesses only, never done the repair on
plastic but have had success with earlier brass floats.  The principle is
the same, only repair materiel will differ.
Place the leakey float in a pot and cover with water. Weigh the float down
so that it is covered completely by the water. Bring the water to near
boiling and watch for bubbles escaping from the float.  Mark every location
you see bubbles comming from, each is a leak.  Simmer untill all bubbles
stop comming from the float.  You will at this point have boiled all the
fuel from inside the float. Remove the float from the water BEFORE turning
down the heat under the pot (or you'll fill your float with water) and
solder (or glue if plastic) up each leak.   
It's easier than it sounds.....really!  Of course simple replacement is
easier still but some of us have tighter LBC budgets than others.....
 Good Luck!
   ___        \______           Ross MacPherson
  / __ \ __ /       /------|)
/  (___)---------/ (___)        1947 MG-TC 3528
                                                1966 MGB-GT 

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