Forum

[John R]

the '89 350 engine is running fine. Carb is an Amal Mk1 Concentric PAV? What's PAV? A bit of Redex might be an option. I regard this stuff highly; I once bought a Peugeot 305 that was transformed from old banger to hottish hatch by a tanksworth of Redex. I think the main thing it did was unblock the jets in the twin-choke carb, but blimey!1400cc, overhead cam, aforesaid carb -suddenly I had a real little belter!

[MadMike]

Gwilly, a shiny piston is not a decoke obviously. The water leak to which you refer was probably allowing water in for a considerable time before making the piston crown nice and shiny. However what about the valve gear? What about the cylinder head and what about the bores and rings. Sorry but there is only one way to decoke and that is to remove the head and barrel, strip the head and clean all internal surfaces correctly. Redex is much suggested as being a decoking agent, but it is actually an Upper Cylinder Lubricant. Thus it reduces friction in the valve/guide area and it may assist in burning off loose sooty type carbon deposits. It is not designed as a decoke agent and it will not remove hard carbon deposits which make it necessary to carry out a full decoke. With our current "summer weather" there are worse ways to spend an afternoon than doing a proper decoke.

[Alan R]

Hi guys-------- have a read of this}----- http://blog.hemmings.com/index.php/2012 ... an-engine/ -------------------------------------- and this}----- http://www.aquamist.co.uk/vbulletin/sho ... .php?t=577 ------------------- I've NOT done it myself (yet) but it would appear that the trick is to use a SPRAY rather than fluid and apply into a HOT engine in small amounts.........Like GWILLY and others I also have seen the results of a water-leaking head gasket (Firt visual sign was the spark plug being cleaned as well)...........Good, old REDEX is a name from our collective past and not seen so much to-day but, I have seen suggestions that the ATF we so covet for our forks and primary chains can give the same results.... Hello MADMIKE, how's yer grossets, me deario ??-------- here's your "Alchemy" for you }----- http://en.wikibooks.org/wiki/Structural ... s_Reaction ----------------- PS, There's no IMPENDING fuel crisis !! We're in one already---- we ( the Public) just don't know it yet, that's all....God help our Grandchildren in 50 years time (ie - Their foreseeable future)------ OK, deleting RANT mode !!

[Gwilly]

Mike, am with you 100% and would definitely not wish to advocate introducing water into an engine as a means of maintenance..

After all a strip down decoke, clean and inspection is the only way to properly assess the top end for wear and integrity.

Think i was merely musing on Johns desire to try water as a decarboniser.... the effects of which i have seen as a side effect of a fault, i.e. blown head gasket.

John if the motor is showing no symptoms associated with heavy carbon build up, then some Redex in the tank would probably do no harm and be all you need to do.

PAV stands for pulsed air valve. A contraption fitted to the later carb models before fuel injection as a means to overcoming/ complying with European emission legislation.

Without which the bikes could not be imported to this fair isle... Works off the inlet manifold, providing a pulsed partial vacuum to the valve which in turn injects air into the exhaust gas at each pulse. Most of these have been removed by owners leaving the inlet stub blanked off in the manifold... Yours is older and bears non of this hi tech shenanigans....

cheers gwilly.

[taper]

I would like to add my bit of knowledge on water in engines for the purpose of de coking . the only time I have observed water in engine compartments that were not designed to accept water as part of the fuel injection system resulted in severe damage to the bright metal parts ,eg pitting and rust , I would not intentionally introduce anything other than petrol/oil/redex to a working engine far better to remove the cyl head and have a good de coking session.

[Leon Novello]

Take notice of how the engine runs better when it`s raining; also a lot of rattles seem to disappear when it rains.

[Robin]

You're right, Leon. Smoother running and perhaps a tad more power in the wet and damp.

[harry b]

no need to de-coke in this country then

[BobF]

The Modern Motor Engineer by Arthur W Judge contained a piece about decoking an engine using an oxy-acetylene torch inserted into the plughole. I had two editions, one of which was pre-war and it was included in that and possibly also in a later edition (circa 1949) which I still have. Presumably the technique was recommended only for engines with cast iron pistons.

I can confirm the use of Carboblast for gas turbines as related by Alan R. I worked for the manufacturers (Bristol Siddeley, later Rolls-Royce). Carboblast was used in the factory on used aluminium compressor blades.

[MadMike]

A couple of things. Bikes do appear to run smoother, and feel punchier when the weather is wet. Firstly the engine runs cooler and as I said in an earlier note the moisture and usually lower air temoperature make for a denser charge going into the combustion chamber. Just for the record riding your bike in the rain will make it wet and dirty, but it will not decoke the engine......but you already knew that. The oxy-acetylene torch trick is simply a crude means of burning off any loose carbon in the combustion chamber. It will do nothing in the valve area and may seriously damage the piston and/or cylinder head. Of course it is not a practical proposition as you will have trouble crrying the bottles whilst riding, if you want to do this on the move to save stripping the top end. The carboblast technique will be a wonderful way to clean out your Turbine Royal Enfield engine. But you will have to eat a bloody lot of walnuts first to get enough shells if you use Alans method.