De-carbon pistons?

[Mr Earl]

The heads are off my M800 (on the way to Speeddog for refurbishment) and I see that the piston-tops are carboned up a bit.  Should I try and remove it, and if so, any technique recommendations?

[hooligan machinist]

 There is a product that you can get at just about any auto parts store.
I don't remember the name brand, but it's a liquid that you dip pistons in and let soak for about an hour or so.
I left the pistons from my old(95) t-bird in it overnight, after that the carbon just rinsed away with water.

[Mr Earl]

I'd hoped to leave the barrels and pistons in place.  Can this stuff be used without soaking, I wonder?  I'll take a look in the local Auto Zone, thanks.

[Buckethead]

If you're leaving the pistons in place, have you tried a a little bit of gasoline on a rag?

[accrocker]

We use BG fuel system cleaner at work to clean carbon buildup from intake valves. Just pour a bit on, and take a wire brush to it a few minutes later. I have done one set of pistons with it as well from a turbo motor. I left them in the block to do it. Just make sure you get the piston to the top of the bore, and don't apply a huge amount of the cleaner. I think that it is available from Napa.

[jim_0068]

magic eraser; that stuff gets anything out 

[He Man]

chuck some seafoam at it. it work wonders. and cheap.

[Ratfink749]

I'm a fan of bringing them up to TDC then using a wire brush to clean them off when I need to.  The other way that works is to put it all back together and while its running, slowly spray intake cleaner into the throttle bodies.  It will clean out the throttle bodies, the intake runners, the valves, and the piston tops.  I've even gone as far as using straight water slowly dumped into the throttle body (while its running at 2000(ish) rpm.), It wont remove the grease and grime in the runners and on the valves, but the steam in the combustion chamber will get rid of the carbon.  (Potentially dangerous to your engine, do this at your own risk)   

[scott_araujo]

Once you get it back together get one of those pump up garden sprayers.  Spray a fine mist of plain water into the intake while running at 3-4k.  Steam cleans.

It may throw some black sludge out the exhaust so if you have a cat you'll want to disconnect it so you don't plug it up.

If you want to attack directly, a nice piece of hard wood cut into a chisel shape can safely be used without worrying about scratching anything metal.

Scott

[ducpainter]

<snip>

If you want to attack directly, a nice piece of hard wood cut into a chisel shape can safely be used without worrying about scratching anything metal.

Scott

We used to use the round end of a hacksaw blade on the 2 strokes. With some care it should work.

[booger]

How long will the de-carboning last? Does it run better afterward? Seems like it would carbon right back up shortly after running the engine. I noticed when doing the valves that the piston tops in my bike are carbony, bike runs great. Maybe it's one of those 'feel good' things we all do sometimes. [moto] 

[Speeddog]

I use a piece of 1/16" aluminum sheet, one end filed to a chisel point.
It's soft enough to not hurt any of the parts.
try to avoid getting the carbon into the gap between the piston and cylinder.

It'd be best to hold the cylinders down with some spacers and nuts on the studs, if you break the base gasket 'seal' it may leak after you've got it all buttoned up and running.

[ducpainter]

How long will the de-carboning last? Does it run better afterward? Seems like it would carbon right back up shortly after running the engine. I noticed when doing the valves that the piston tops in my bike are carbony, bike runs great. Maybe it's one of those 'feel good' things we all do sometimes. [moto] 

Some carbon is typical. It would have to be excessive to cause problems, although it would raise compression slightly so it could actually run better.

[scott_araujo]

A little is fine.  Optimum would be none but you're burning fossil fuel, you're going to get some over time.  If you get too much it gets cakey and also tends to get hot as the engine is running, especially anything on the cylinder head.  That's bad.  It starts to glow cherry red and the retained heat can cause predetonation or pinging, poor running, and subsequent loss of power.

Scott

[Mr Earl]

Can someone quantify what is a little carbon vs a lot?  There's kind of a light frosting of it on the vertical cylinder, and just a bit thicker on the horizontal.  Hard to measure.  The horizontal cylinder's piston deposit is brownish and kind of gummy, the vertical is black and dry.  Differences in mixture?

That's a good tip on the cylinder studs, Speeddog, thanks!