On 06/10/2011 12:00 AM, IanM wrote:
Pete C. wrote:
Ed Huntress wrote:
"Bill Martin" wrote in message
...
On 06/09/2011 10:51 AM, Ed Huntress wrote:
"Bill wrote in message
...
On 06/08/2011 12:37 PM, Ed Huntress wrote:
wrote in message
...
Ed Huntress wrote:

What do you think of this "stuff" for cleaning the grunge out of a
two-stroke expansion chamber? Castor oil is great for bearing
life, but
kinda messy in the exhaust... thanks for any suggestions.
I doubt if it would do much, Bill. This is straight lye, with goop
in it
to
keep it from sliding off of surfaces. It will saponify fats and
oils, and
it
will attack some polymers and proteins (like the ones in your body
cells),
but it won't touch carbon.

If the problem is partially-burned castor oil with some carbon
mixed in,
it
might work. But, chemically, it's no different from "heavy duty"
version
of
Easy-Off oven cleaner. You might try that first. It's less hassle for
small
projects.

I've never had much luck finding a chemical way to get carbon out
of an
engine. There supposedly is some treatment but I can't remember
what it
is,
nor have I tried it. When I did it, I used scrapers. Ugh.

Consider the nature of the deposit - thermally polymerised vegetable oil
+ carbon. If it was a drying oil (e.g. boiled linseed oil) + carbon
black it would be a paint so for easy decoking, use paint stripper.
Obviously don't use an alkali (caustic) stripper on aluminium parts, but
dichloromethane (methylene chloride) based ones are safe on all metals
found in an engine. Wash off any residue with methylated spirits (or if
you used an alkali stripper just with water).

CAUTION: It will attack seals, gaskets and of course paint!

Had not considered paint stripper, no Al. here, so worth a try.


The only notable problem is that plastic toothbrushes don't last long in
contact with dichloromethane based strippers, which is a pity as they
are ideal for cleaning ring grooves, round valve seats etc.

Tried the oven cleaner already, not so great. Sandblast would be
interesting, but the shape of the pipe makes it impossible to really
get
inside with a normal nozzle. I'm actually desperate enough to be
thinking
of making a high velocity water jet with sand entrainment to try and
scrape the gunk off "around the corner" of the chamber. Right now, I
can
get a reasonable cleanout only if I'm willing to spend hours fussing
with
it, and getting pretty grubby in the process. Must be a better way...

bill
Yeah, well, good luck. If you find something that works, let us know. I
don't have to de-coke old British engine cylinder heads anymore, but
it may
be useful for something. d8-)

--
Ed Huntress

"Extrude-hone" comes to mind, forcing an abrasive paste/slury through
the inaccessible passages. Perhaps that will spark some DIY ideas...

I've seen a marine engineer (big ships!) burn out the carbon from a
bronze exhaust system off a launch with a Stuart Turner two stroke
engine - remove the exhaust from the boat, remove all the lagging, pour
a cup full of petrol down it and shake well, build a bonfire round the
whole exhaust and as soon as the flames coming out the far end died
away, hook up a vacuum cleaner on blow! The result was an absolute
inferno out of the manifold end and a dull red glow from the pipe.
Apparently the trick is to rake the bonfire away from the exhaust once
you have the glow and restrict the air supply as well if that doesn't
control it as you DON'T want a BRIGHT red glow ;-) It actually took
something like fifteen minutes to get the glow most of the way down the
exhaust, at which point the engineer commented that it was now done, and
he'd just let the bonfire burn out and it would be ready to reinstall
the next day and it was also annealed as a side benefit!

I've never had the need or desire to try it myself . . . . YMMV!

Good thing it was a bronze part...I once tried gas welding a new header
onto a steel expansion chamber, and managed to diffuse enough of the
carbon inside the pipe 'into' the steel, that it just snapped off, so
darned brittle!
-bill