Saving Old Seagulls

Chuky - you put your own piston in the Caustic, I've got better things to do with mine . . .

The point being, please don't recommend things you've never tried, that would obviously be very detrimental to someone's pride & joy, as some of our members might be under the impression, that you knew what you were talking about.

Charles he is wanting to decoke his cylinder head/block. I have decoked aluminium cylinder heads with caustic soda very satisfactorily. The block would be cleaned very well also. And the dishwasher will finish the job beautifully.

The piston obviously would not require any chemical cleaning as scraping would suffice. At my time of life, I have no need to advise anything which I have not tested to my satisfaction.

Are you sure you mean caustic soda?
Because aluminium is so reactive in caustic.

I agree, it can cause pitting in a matter of hours

rosbullterier wrote: I have decoked aluminium cylinder heads with caustic soda very satisfactorily.

Surely there is some misunderstanding or ill judged humour in suggesting the use of caustic soda to decoke ali heads and pistons?

Normally in de-coking you remove the coke from the Al object. NaOH removes the Al object from the coke......

Caustic soda = lye = sodium hydroxide = NaOH= not good news for aluminium.........or human tissue for that matter....


Peter

maybe we are talking about two different types(strengths) of caustic soda. the powder i get from my local corner store is so weak you could almost bathe in it yet the flakes i remember my dad using when i was a kid were very scary indeed...... what about hydrochloric acid?

What you are taking about is called washing soda. I doubt if it is as strong as caustic soda. I didn't clean my brasswork up as well as expected
If they are one and the same I was very disappointed

Brick acid works well but it’s far too aggressive to use on ally. It’s good on de-scaling heads (the upside down trick poring through the outlet). Check the percentage of acid in its content before purchase ( I use MIXIT) not sure if you can still buy this.
For de-cokeing the best method for engine parts is soak in diesel and a old tooth brush and gently scrub.

washing soda is sodium carbonate(Na2CO3) . what i bought was definitely caustic soda(NaOH) but it was a very weak batch it seemed to me. i was wondering about hydrochloric acid(HCl) but i might give the diesel a try first.... cheers
Bill

Charles uk wrote:Rbt put one of your pistons in warm caustic for an hour & let us know the result.

"I can see into the future" did the aluminium start to dissolve?

Before the black crap did? which is a perfectly normal by product of a 2 stroke internal combustion engine.

Stop! This may be a bit of a joke but somebody may mis-understand. Never use caustic soda or any other alkali on aluminium. It will destroy the piston. Just give it a bit of a gentle scrape, nothing too fussy, you are not tuning a racing engine, put the engine back together and enjoy your seagull.

Regards.

Alan

All strong alkalis and acids will damage aluminium very quickly. Even if diluted they will still do damage more rapidly than expected. For baked on carbon removal from aluminium parts, use a methylene chloride based paint stripper. Caustic (low V.O.C. 'environmentally friendly') paint strippers are totally unsuitable. If it recommends neutralisation with methylated spirits (meths), it is probably the right stuff.

I have used Nitromors with good results brushed on and scrubbed a few minutes later with an old toothbrush. Rinse off the brush in meths immediately after use or it will end up a melted gooey mess and *DONT* get any of it on you or any plastic part or painted surface you want to keep. A clean aluminium 'takeaway' type food storage container is good to work in. Rinse all cleaned parts thoroughly in meths and they are ready for inspection and hopefully reuse.

It will also work on steel parts but as they are harder mechanical abrasion may be cheaper and faster. It may be very helpful with stuck piston rings (but not if they are badly rusted as it only dissolves organics) and glazed bores be3fore touching up the honing. Also does a good job on diesel pre-combustion chambers and carboned up 'classic' spark plugs like original 8COMs.

Had a villiers engine on a James scooter in the 1960's. That was always "whiskering". In the end I had the plug hand tight only. A three pronged plug was the final solution.