Re: [ihc] Re: Scout warm-up issues

["Ryan Moore" <baradium@xxxxxxxxxxx>]

----- Original Message ----- 
From: "Tom Anderson" <ande1054@domain.elided>
To: <ihc@domain.elided>
Sent: Saturday, January 31, 2004 11:22
Subject: [ihc] Re: Scout warm-up issues


> Ryan wrote:
>
> >>> This last week I paid particular attention to the scout's warm up to
see
> >>> exactly what it does when it gets to it's trouble spot.
>
> >>> It always starts great and it'll run perfectly regardless of temp, I'd
> >>> venture to guess I could kick off the choke immediately too and it'd
be
> >> fine
> >>> at first.
>
> >>> Here's what happens...
>
> >>> It'll start great and be running along fine.  let it idle to warm up.
> >> It's
> >>> running fine.  Then the rpm drops a little. Takes a while before it
starts
> >>> dropping but once it does it's fairly quick.  A slow and steady
decline in
> >>> rpm until it bottoms out at around 400 or 500 rpm sounding like it's
only
> >>> hitting on a few cylinders (I need to get a tach so I can verify the
> >> rpms).
>
> My '77 Scout does the same thing when the ambient temp is around 30
> to 40 F, and the humidity is high. I suspect that you have
> conditions similar to that most of the winter. You are in GA,
> right? The carb is icing up. The ice chokes the air off, causing a
> rich mixture. Does the exhaust smell bad when the problem occurs?
> Does it blow black smoke? Those two symptoms indicate an excessively
> rich mixture. If you look down the carb, when the problem is
> ocurring, you may be able to see the ice in the venturis.
>

I'm in TN.  Going to have to pay more attention, it's been pretty cold here
recently (high in the 20's yesterday)  next time I get where it stays below
freezing I'll pay attention to see if it does that.

One thing though, while it's doing that giving it throttle still does
increase the rpms etc, just not smoothly or anything.  Seems that if there
was enough ice to do that to the idle, the throttle wouldn't be able to add
any airflow.  Maybe the ice is mainly on the flapper blocking off air mostly
when idling and less as you increase throttle?  Would make another symptom
make sense, there's a spot where once you get past a certain throttle
setting the throttle seems to go away almost completely in a surge.

> >>> It'll stay that way for a while, can't touch anything becuase kicking
off
> >>> the fast idle will cause it to just die.  It'll do that for a few
minutes
> >>> and then out of nowhere the idle will bump up a notch, not a whole
lot,
> >> just
> >>> 50 rpms or so, it's a sudden surge.  After that though it starts the
same
> >>> progression as initially except in reverse until it's at normal fast
idle.
>
> The carb is getting warm enough to start melting the ice.
>

That and the exhaust is getting warm enough that the warm air intake has an
effect maybe?

> >>> Then I can kick the fast idle off and go.   I can drive before then
but I
> >>> have to be careful to keep some pedal in or it'll die (doesn't bother
me
> >> too
> >>> much, I like to let the scout warm up before driving anyway).  It does
> >> kind
> >>> of bother me though the way it does that.
>
> >>> It runs really bad during that period.  Sitting there barely hitting,
> >> whole
> >>> scout shuddering and rocking a little as the engine hits along.  It's
> >> going
> >>> slow enough that I want to say I could easily count the number of
loops my
> >>> alternator belt does while it's doing that (yeah a tach would really
help
> >> on
> >>> getting that RPM, I'm kind of curious how fast it's going).
>
> >>> It's a pretty drastic difference.  Takes about 30 seconds I'd say to
go
> >> from
> >>> initial great running to bad and another 30 seconds to get good again
> >> after
> >>> a few minutes of barely puttering along.  Also, it only does it when
it's
> >>> cold.
>
> >>> I've tried to mess with the choke some while it's doing that with no
> >>> effect... any suggestions on what I should look at?
>
> Your heat riser valve. Mine is not functional. The spring is
> broken, so the valve stays open all the time. When the engine is
> cold, the counter weight on the valve should be up. The spring
> should hold it there. When you push the weight down, it should
> spring back up, when released. When the engine warms up, the
> bimetal spring relaxes, and the weight opens the valve.
>
<snip>
>
> > ------------------------------
>
> > Yes it has a heat riser.  It moves freely.  I'm assuming it's working
> > properly?
>
> Just because the valve moves freely, doesn't mean it's working. The
> valve should spring to the closed position (counter weight up),
> when the engine is cold.
>

What I mean is, it moves properly too, I've paid attention to it.  The thing
is that I don't know if the flapper is completely intact.  It does have an
effect on the exhaust I think, but it's not all that large of one at all.
The exhaust has never been unbolted, still running original exhaust (factory
duals).  Only thing that's been done is a new exhaust gasket on the
passenger side.  Need a new donut gasket there too though.. but it's not all
that horrible of a leak.

Thanks,
Ryan