[adal]

Can any of the members tell me please if there have used water to to decarbon the engine on a lawnmower before if so does it do a good job or am I better off removing the head  and scraping the carbon off

[Gwiz]

Take the head off and scrape!
Water is a no-no.

Get a new head gasket, don't reuse the old one.

[Dopey113]

You have to be VERY careful scraping, you shouldn't have carbon on the head? you can get additives you add to the petrol and that should clean it for you

[Amilo]

I am from an engineering back ground and  I have never hear of water being used to de-carbon a engine, except maybe for washing your hands after the job.

I quick run down on a "decoke" job, but first a note of information, just cleaning the carbon off the piston top and the cylinder head without other remedial work can actual make things worse, by removing the carbon you will lower the compression ratio  and without reconditioning the piston  and the valves (if its a 4 stroke) you will have lower power than you had before.

What makes you think the engine needs a de-coke?

[adal]

Its with the lawnmower being Twelve years old I was thinking it may have a build up of carbon as I have only had it for four years and I do not know if the lad I got it of ever de-carbon the head.  if it needs to be done what would be the best way as Gwiz says it’s a no no using water to get rid of the carbon and to take the head off and scrape the carbon off. I think the water my self may get past the piston rings and end up in sump if you type de-carbon a engine with water on u-tube you will see them using it on cars - bikes – lawnmowers 

[smud6ie]

I have a 5 hp B&S on a rotavator bought new in 1976 ,its still in use and the head has never been off.
In 50 odd years of repairing machinery I can't recall decarbonizing an engine that was not showing  symptoms of poor running.
smud6ie

[Gwiz]

In 50 odd years of repairing machinery I can't recall decarbonizing an engine that was not showing  symptoms of poor running.
smud6ie

Have you worked on the new "Four Mix" Stihl engines? we have to decarbonize those with monotonous regularity!

[smud6ie]

In 50 odd years of repairing machinery I can't recall decarbonizing an engine that was not showing  symptoms of poor running.
smud6ie

Have you worked on the new "Four Mix" Stihl engines? we have to decarbonize those with monotonous regularity!

Only had to unblock the Exhaust /port on back pack blowers  but there are symptoms
smud6ie
smud6ie

[Gwiz]

Go on, decoke one. Try a BR600, You KNOW you want to!!

[Amilo]

Its with the lawnmower being Twelve years old I was thinking it may have a build up of carbon as I have only had it for four years and I do not know if the lad I got it of ever de-carbon the head.  if it needs to be done what would be the best way as Gwiz says it’s a no no using water to get rid of the carbon and to take the head off and scrape the carbon off. I think the water my self may get past the piston rings and end up in sump if you type de-carbon a engine with water on u-tube you will see them using it on cars - bikes – lawnmowers 

Forget the water!!! if its not broke then don't fix it, just sit back on a sunny day and admire the wife pushing it back and forth!