Cleaning Carbies and Pistons

If you are a karting or motor bike fan, or a backyard mower mechanic then it’s likely that you’ll know the pain of old fuel that has turned into varnish.  Bet you wear the same despondent look when you see a blackened piston.

For the home mechanic, this is probably the most useful function of an ultrasonic cleaner – to clean out that gunked up carbie.  The great thing is that it can do the job without resorting to those seriously caustic solvents.

Even so, there are still two schools of thought on what additive to use in the ultrasonic tank.  You guessed it – green vs more aggressive.  We caution against using substances that will require the operator to put on the protective clothing and respirator and hold their breath.

Option 1 – More Aggressive

In the industry, we know of guys who still swear by the caustic products, which is fine as long as they tell us that they are using them before we pay a visit.

If they are using CT14 (generally marketed as truck or bilge wash) then this is a safe option.  The safety data sheet on CT14 says that it is non-flammable and in other respects pretty inoffensive.  Of course, you won’t want to drink it, but otherwise it’s about as safe as you can find, while still giving good results.  For carbies, half a cup in a 12 litre tank is as much as you need.  When last we checked, you could get a 5 litre concentrate at Supercheap Auto for a touch under $40.  Similar price from Repco.  As long as the tank is heated adequately (around 70C+), it should only take about 15 minutes to clean a dirty carbie, more or less.  A hint though – it can take quite a while to get the tank up to that temperature.  We would recommend using the cleaning function as well as the heater, and put the lid on.  That way you won’t be waiting around twiddling your thumbs.   Brett, our customer in the engine reconditioning business, recommends giving it a good blow out with compressed air after cleaning, just to make sure the gunk has come off and been sent to keeper.

For pistons, he says it might take a couple of hours to get them clean, especially the top – really bad ones can be left to soak in CT14 overnight – the next morning you should find the carbon has softened and the ultrasonic will have an easier job of finishing it off.

Back to the ‘not so gentle’ products – some are also flammable. Cool.  Because the flash point can be lowered after using an ultrsonic cleaner. Now we have the worst of both worlds.  It is worth noting very prominently, that flammable products do NOT belong in an ultrasonic cleaner, whether heated or not.  If you must use these products, then do yourself, and your loved ones, a favour.  Soak the carbie or piston in a tank well away from the ultrasonic.  Only after the substance has evaporated off, or has been thoroughly rinsed off, should you place the item in the ultrasonic for the next stage of cleaning.  High powered cleaning at 60C in an ultrasonic is a formula for pyrotechnics, not safety.

A very popular solvent is good old acetone, found in almost every woman’s survival kit.  As gossip girl will happily tell – acetone is great to remove nail polish.  It is also seriously flammable stuff.  Play it safe.  Wait until the acetone evaporates off the piston or carbie before placing in the ultrasonic tank for the perfect clean.

Option 2 – Go the Green. 

Now, the green alternative is to try products that are kinder to people and to the environment when the cleaning is over.  On our list of more environmentally (and people) friendly products are Simple Green and Kenco SHIFT-IT Heavy Duty Cleaner.  Simple Green is very popular in the USA where it is widely available.  It’s a biodegradable product that can be bought on the internet from the Australian distributor (shipped from Adelaide).  We have also seen it at Bunnings and Blackwoods – so it might be worth a trip down to your local store (or check them on line), to save on freight by picking it up when you buy your other hardware staples.  NB. There is a range of Simple Green cleaning products – you want the industrial strength cleaner.

Simple Green ships as a concentrate, so one bottle goes a long way.  We have customers who are very big in reconditioning carbies who swear by it.  At the other end of the spectrum we have an elderly customer painstakingly restoring his beloved vintage roadster in WA, who is likewise a big fan of Simple Green for its effectiveness and for its reputation for safety.

The Kenco product does not appear to be as widely used by our customers – perhaps it is just less well known.  Anyway, Paul the grubhunter uses it to good effect, and is a big supporter of both its effect and kindness to worker and environment.  You can get it at the regular auto product stores – about $12 for a 750ml spray bottle – although larger bottles (up to 5L) are also available.

As with many of these cleaning tasks, there is no magic formula for the time the cleaning job will take.  Let yourself be guided by common sense.  Time in the cleaner is a function of 5 factors:

  1. Power of the machine (ie Watts)
  2. Frequency of your ultrasonic (lower frequency (typically 20-25kHz) has more ‘oomph’, but not so good for detail – eg blind holes and thread vs higher frequency (40-45kHz) which is better for fine detail and more consistent across a surface and better for gentle cleaning results)
  3. Temperature – as a general rule, 60C will be the best operating temperature for an ultrasonic cleaner, although this temperature is too hot for some materials.  Be aware that at 60C evaporation can be faster than you might think.  So keep an eye on the fluid level in the tank and always top up fluids as required (Think SAFE.  Turn unit off and disconnect from power first).  Please do not even THINK of putting a flammable product in an ultrasonic and running the unit at 60C.  The cavitation effect helps to lower the ignition point of fluids – don’t say you weren’t warned!
  4. Amount of Dirty Gear you place in the ultrasonic tank.  The higher the surface area to be cleaned, the slower will be the result.  and
  5. Type of Contamination what is on it – eg burned carbon vs light soiling.

So, you need to be flexible and keep an eye on how it is going.   Just remove the item for examination about every 10-15 minutes, so that you know when it’s done, and you can move on to your next subject for cleaning.  That approach will also help you to maintain the correct fluid level in the tank, so you don’t damage the ultrasonic or the heater in the process.

NB. Simple Green needs to be used carefully with aluminium products, as it may cause oxidation if contact is extended.  Remove item from the solution as soon as it is cleaned, and ensure that all traces of Simple Green are rinsed thoroughly off your carbie.  If you see evidence of aluminium oxide you can remove it with an aluminium polish like Autosol or Briteshine.

Dual Frequency or Intello-Cleaning.  If you are using an ultrasonic with dual frequencies, we would suggest running it first on low frequency for 30 minutes to blast the heavy duty crud.  Examine the item after first cycle and extend low frequency cleaning to continue ‘blast mode’, or switch to high frequency operation to ensure that fine detail areas are covered.  Adjust cleaning based on the cleaning result you experience.

If you are using an Intelloclean or similar sweep style ultrasonic cleaner the process is simple.  Select your sweep function and leave the machine to cycle through low and high frequencies for about 30 minutes.  You can also use the Turbo function, but go easy if the item you are cleaning is a soft alloy.  Examine the item and repeat as necessary.

If you remember that an ultrasonic cleaner of 100W will take 10 hours to consume a kW/hr of electricity, and that kWhr still only costs about 27cents, it is a very cheap cleaning process.  Add say 25 cents of Simple Green or Kenco liquid to the tank and you are looking at petty cash indeed.  HINT: Try the shooter’s tip – use a Pyrex beaker or jug to hold your parts inside the basket of the ultrasonic’s tank.  That way you can ration the Simple Green/Kenco or caustic brew to just treat the carbie or piston while the rest of the tank is filled with tap water. A final caution – no flammable items in the ultrasonic tank.

  1. Always turn machine off before removing item from tank for inspection.  Never permit fingers, hands, or any other body part to enter the liquid of the tank while the ultrasonic cleaner is operating.  Damage to living tissue will result, even if you cannot see it.
  2. A little reality check.  There are some videos on you tube that show a dirty motor going in, and, hey presto!  a brand new looking motor emerges.  We find these a bit deceptive, as they imply that an ultrasonic cleaner will clean and polish and restore a motor to brand new condition on their own.  There is often no indication of how long the motor has been worked on, how powerful the ultrasonic cleaner, and what, if any, sort of additive or solvent is used in the video.  An ultrasonic cleaner will clean, but carboned metal normally requires an additive to help break it down.  And polishing – well just like with jewellery – this is an additional process.  Once an item is clean it can then be polished.
Liquid Glass Oz designs quality ultrasonic cleaners for commercial operations in Australia and New Zealand (N18973)

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