Stuck/Frozen carb butterfly valve

Folks,

I'm working on a '94 Honda VFR750 that has been sitting a couple of
years. The throttle was stuck closed, and some digging around showed it
to be one of the throttle butterflies. It has some hard varnish on it
and is a little darker than the others. Inspection of a float bowl
reveals only some varnish depositsn nothing green or growing. I've been
doing my reading and have a couple of spray cans of Berryman B-12 at
the ready, but I'm hesitant to just spray it all over everything for
fear of damaging the rubber bits that may be hiding in the throttle
shafts. So far, I've sprayed a little bit in the venturis and tried
soaking the butterflies with WD-40 as well, but nothing's budging.

Do I need to bite the bullet, break the carbs apart and tank clean
them, or is there a less invasive option?

 

B-12 won't hurt any rubber part that hasn't already perished from
drying out and is already crumbling. Rubber diaphragms that have been
cleaned with B-12 will soften and swell, then they return to normal
size. I've been cleaning carburetors with B-12 for
30 years now and have never damaged any rubber parts with it.

If the carbs are off the machine don't break the individual carbs apart
from the cluster.
Keep the shafts all clamped together and the carbs attached to whatever
brackets they
are bolted to, but strip the brass parts out and spritz through all the
orifices and passages.

I've never seen a carburetor in such bad condition that it needed to be
cleaned in a tank and gawd only knows what kind of acids or caustic
solutions are in tanks intended for cleaning automobile carburetors.
Part of the carb rebuilding process is
chemical etching or chemical polishing to remove corrosion and whatever
chemical is in there might remove metal from the precision drilled
orifices in the carburetor body.

 

Thanks for the vote of confidence. I went back and looked the butterfly
over again, and this time looked at it from the top by retracting the
slide. It did have a little bit of green corrosion around its rim. I
believe it's either frozen around the rim or in its pivot shaft. I
sprayed some B12 in and tilted the carbs so that the B12 is pooled over
the pivot shaft and will let it soak that way for a day. If it's still
not free, I'll soak the opposite side of the pivot shaft.

I'm hesitant to apply any significant pressure to the throttle
connection out of fear of bending some very precise parts. Short of
directly whacking the butterfly with a mallet, what's the best way to
get it loose? Keep spraying and soaking?

Thanks!

 

Have you tried turning the master idle knob clockwise to see if the
butterflies move?

Another way would be to put a small crescent wrench on one of the
clamps that attaches the two throttle shaft together and gently turning
the shaft.

 

Are you sure the throttle cables aren't siezed up?

If the cleaner is going where it should go, the throttle shafts will
easily be cleaned of gum and varnish. You could try spraying the shafts
from the insides of the carbs---maybe that's what you mean by "soak[ing]
the opposite side of the pivot shaft".

 

Generally I like Kroil for frozen parts. Might be more effective
than carb cleaner. I don't think you'd have trouble with rubber bits.
Kroil is a pentrating oil.

If you're sure you're trying to turn it in the right direction, you're
dealing with a mechanical problem and should treat it as such.

Can you remove the throttle linkage, put a well fitting wrench on
the shaft end and apply some very mild torque ?

 

Success!

Matt: no, it's not the throttle cables. That's the first thing I
checked. I have the carb assembly off the bike now.

I sprayed and soaked the shaft some more tonight, then did as Rob
suggested to take some of the throttle linkage out of the equation: put
a wrench on the nut at the end of the throttle shaft that the stuck
carb was on and slowly twisted.

Nothing popped; it just slowly opened and...stayed where I left it. I
kept spraying, soaking, and turning the shaft until I could do it by
hand. Things eventually worked free to the point that the return spring
was actually closing the butterfly. From that point, a few minutes of
working the shaft back and forth had it snapping right back like it
should!

Now on to actually cleaning the carbs...

By the way, I did notice that the B12 was dissolving the toothbrush I
was working with, so I'm still going to try to keep it away from the
rubber parts.

Thanks everyone for your help!

 

1. The ingredients list on B-12 is remarkably similar to that of lacquer
thinner -- my favorite universal cleanser. However, some of those
ingredients *will* dissolve cheap plastics (like that toothbrush). Almost
any part meant to be in a carb will not be affected.
2. If you do remove small parts from the carbs, keep track of which carb
they came from -- Can't guarantee it, but it's likely that they will be more
"comfortable" going back in the same holes they came out of...
3. Kroil is an *extreme* penetrating oil. For mechanical parts that need
freeing, it will do miracles. (It's so good that many rifle nuts use it for
cleaning their barrels -- it can actually get under a lot of the stuff
that's been heat & pressure deposited on the steel...)

 

Glad you're moving ahead.

You probably ought to just replace the rubber parts. I can't imagine
the O rings or diaphragms being in very good shape after sitting
so long.