Hi Phillip,
I'll throw in my two cents here:
If it's backfiring out of the carbs (as opposed to out of
the exhaust), it'll always look white, because it's fuel
mist being spit out there. Backfiring through the carbs
makes me think it's an intake vacuum lea,k or timing.
Make sure all the carb and manifold nuts & bolts are tight,
and recheck the timing just to be sure. You can spray WD40
(or pretty much anything) around the edges of the sealing
surfaces (with the engine running) and listen carefully for
any change in the idle speed or backfiring frequency.. When
you hear a significant change, you've found a vacuum leak.
I've found that even ratty old SUs can be made to
work pretty well if everything else is right. Don't run out
and buy new ones just yet! Old leaky carbs can make it hard to
get a nice, even, low idle, but otherwise are often fine.
Another thing to try: disconnect and plug the vacuum line
to the distributor - the vacuum canister could be leaking if the
diaphragm is bad, and it's nice to hold the timing fairly
steady when you're chasing vacuum leaks.. Also check the
other connections on the manifold, and the breather hose
from the timing cover to the carbs..
I think your float bowl problem is that the needle valve
(in the float bowl cover) is sticking. Disconnect the hose
from the fuel inlet, remove the cover, and put an extra piece of
hose on the inlet so you can blow into it. Hold the cover
right-side up (like it was still on the float bowl) and move
the float up and down while blowing into the inlet. As you
raise the float, the needle valve should close and stop the
air flow. If it doesn't, poke at it, prod it, spray it with carb
cleaner, tap lightly on the side with a screwdriver handle,
etc., to try to dislodge any bits of dirt in the needle
valve. If this still doesn't work, take the needle valve
out, inspect the tip and the seat, and replace it if
necessary.
Fuel shouldn't spill from the float bowl even with a dodgy
gasket (well, maybe just a little), but if the needle valve
isn't working, it will leak out of the first place it
finds..
Good Luck!
-Hans ('58 Bugeye, '62 Lotus 7 (1275, bastard, in progress))
On Tue, 28 Jul 1998 23:36:01 EDT Philip Hubbard wrote:
> Hmmmm, a bit more work on my float bowl overflow problem tonight.
>
> Looked to see if the float levels needed adjustment. Both were within the
> 1/8"-3/16" clearance suggested by Haynes. Don't know how I'd adjust them
> anyway as it says to bend the lever as necessary and I see no lever. My
> plastic floats sit directly on the needle valves connected to the underside
> of the float lid by a pin. I have HS2s BTW (AUD549F).
>
> Flushed out some gas through the jets with a turkey baster in the float
> bowl. Didn't seem to be any clogs there that would cause rough running.
>
> I really think my overflow might be the gasket at the float bowl as I
> suggested earlier in spite of some list thought that this probably isn't
> it. I say that because when I took the float bowl lid off I noted where
> the gasket was least intact. That is precisely where it overflowed and no
> where else really.
>
> Mixture adjustment. Really thought (and still think likely) that I was
> running too rich based on the fouled spark plugs. Unless it turns out my
> points are bad enough to do this. However, as I've mentioned earlier, when
> I rev the engine by pulling on the throttle cable by hand, I'm getting
> backfire out the carbs. On the theory that white smoke is too lean and
> black too rich, I'm too lean. Looks whitish to me. And it's backfiring
> equally out of both carbs. I tried to richen the mixture, but I went about
> half a full turn and still getting whitish smoke. Don't know if I need to
> go further but I stopped as I noticed the gas was leaking too much for any
> kind of safety. I did notice that it started to idle quite nicely, so
> maybe I was starving it and the fouled plugs is from something else. Would
> explain a bit why I had to run full choke to get home the other night.
>
> Another thing I noticed on the carbs. The front carb has some gouges in
> the beveled part you can see with the piston down. (Don't you just love my
> command of the technical lingo. :) ) There are three or four of them.
> Don't know if they would have any real effect on performance, but I wonder
> what fault could have put them there?
>
> Still debating whether to rebuild the beasts, just be content to continue
> to fiddle or buy a fresh pair, but not brand spanking new - seems too
> expensive for now.
>
> That's it for carbs tonight.
>
> Philip
> 1974 Damask Midget - Arioch, Lord of Chaos
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