Decoking an aluminium head

Hello Mick,

The old books would recommend a dulled flat tip screwdriver to nibble away at the caked carbon on both cylinder head and piston top, a thick smear of grease around the the top of the cylinder bore will catch the chips and they can be wiped away along with the grease. Although, with the newer fuels available I'm not sure if a decoke is necessary anymore, I haven't bothered to do so with any of my older bikes and my SR500 Yamaha with its OHC would be a pain to decoke every spring.

Cheers!

Albert.

I'd recommend a brass rotary brush rather than tediously doing it by hand! Never use anything with steel in it and make sure the brush is brass right through and not brass plated steel - a magnet will tell you. A reckon the blunt screwdriver idea was a carry-over from the iron head days and not to be trusted! I'm sure there are chemicals you can use too. Dunno what though. I used to make up aluminium or brass scrapersfrom scrap to get the worst off.

Cheers, Lionel

Previously wrote:

Hi.

Are then any tools that are safe to use to remove the coke from an Aluminium head? Is a Brass rotary wire brush safe? Are there any solvents? Any tips/tricks/ cunning tools will be appreciated.

Cheers. Mick Pond.

hello to clean Aluminium Heads I have used Rubbarb juice and it work great but you need to boil you cylinder head ? of about a hour ,you need a Big pan ? for that ? but it does come out like new ? Yours Anna J Dixon

Hello All,

Rhubarb juice? Wouldn't a strong solution of laundry detergent be easier and much cheaper! Set up a metal pail outside over a cheap camp stove, place some metal blocks to keep the head, barrel, cases or what ever else above the bottom of the pail, fire up the stove and find something to do for a while.

The spray type carburetor/fuel injector cleaners might soften the baked on carbon inside the combustion chamber, I know it eats fuel deposits in the carb throat and on the outside of the instrument itself.

A rotary brass brush on a Dremel type tool certainly gets into things, I've used mine extensively to polish bits inside my 19s engine. The small brass bristled "tooth brushes" seen at hardware stores work nicely too.

Brass or aluminum scrapers will work nicely too, an old flat file with the end ground to a radius makes a good gasket scraper too. I have done the "dulled screwdriver" trick and it does work, the the old books said to be gentle about it so's not to scratch up the piston top or the head, the key word being "gentle" a little finesse goes a long ways.

Regards,

Albert.

Michael Pond previously wrote on Sunday 6th February 2011 at 17.41hrs:

Thank you all for the tips/ideas. I think I will start with a combination of Carb. cleaner/Brass Rotary brush. I would love to try the boiling in Rubarb juice but don't have a big enough pan.

Cheers. Mick.

Hello Mick,

The most effective de-coke brew by a long way is aerosol gasket-remover. It's evil stuff, so should really be used outdoors. Wear a mask and rubber gloves as well!

After spraying on and leaving for 15 minutes, most carbon depositscan be rubbed off with a small wooden stick.Any stubborn areas might need a second go. Then a rinse (with parrafin)and brush off should have the job done with no damage, in less than 1/2 an hour. You'll have the rest of the afternoon toget on with giving the valve seats a freshen up.

I don't know about modern fuels being the reason for less frequent de-cokes. Leaner running along withstricter emission regulations for modern vehicles more like. Also, the majority of classic owners hardly use their vehicles. Just ask your local MOT tester, he'll tell you of all the Classic 'bikers' & Classic car owners who's machines barely turn a wheel, apart from the journey down to his shop and their clubhouse.

Paul

Rhubarb juice is a mild acid but not too easy to get hold of unless you happen to have a lot of rhubarb trees (). Go to a home brew shop (or Chemist) and get some citric acid - not so nasty and is also edible! I reckon a strong solution to start with, with the valves in and the head upside down. But be careful as it WILL eat into the ally eventually. This also makes an excellent descaler for kettles and taps, especially as it's non-toxic, unlike commercial descalers.

Many years ago I found that the best decoker was water in the oil! Not intentional though! We had an Austin Ambassador (the wedge front car with "O" series 1.7lengine) with a leaky cylinder head. The oil turned to something looking like coffee, but it still ran fine! When I took the head off I found the gasket had failed between an oil and waterway - hence the water getting into the oil, BUT the head, bore and pistons were spotlessly clean and shiny! No apparent damage at all. No scoring to the bores, yet I'd done 100s of miles with it like that before I got "A Round Tuit"! At the time I was commuting daily from Southampton to Wareham, Dorset. ("Bell's Orchard", for anyone who knows the place). That's over 50 miles each way, 500+ miles a week! I was never easy on the loud pedal!

Good luck, Lionel