OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Briggs & Stratton Engines How do I remove carbon deposits

Hi Everyone,
Total amateur here! I have read in a few spots about 'removing carbon' and 'decarbonising' etc. After an epic struggle I have now finally removed the valves from my B&S. There is a lot of carbon build up but I have no idea how its supposed to be removed. on the exhaust valve stem for example. I don't want to scrape it with something in case that is the wrong thing to do.

So the question is...is there some sort of stuff i should be using to aid in carbon removal? solvent? degreaser? Any advice welcome!

thanks in advance to the experts :-)
Dave

I have wondered about this myself, and it got me thinking back to the time I worked in Subaru spare parts where i used to sell a lot of their Upper Engine Cleaner.
This stuff is way toxic and gives off some wicked fumes when the motor is started but many people swear by it.
We used to have mechanics from other dealerships come to buy it, which i thought was odd..... but that goes to show how well this stuff is regarded.
Search for Subaru Upper Engine Cleaner and you will find many posts about how good it is.
I have never used it myself but i think i will buy a can soon to clean out some 2 stroke mowers.

I have an opposite view to bud540, because I just don't like inhaling toxic fumes: the effects can stay with you for a long time (like forever, for instance). Fumes are sometimes difficult to avoid, but this situation isn't one of those cases. I have always cleaned valves by scraping them with a knife blade. If you keep the blade at an acute angle to the stem, and always move it parallel to the valve stem (i.e. don't let the blade edge run across the valve) you will not do any harm to the valve (but watch out for harm to your fingers). Some people use rotary wire brushes for the job, but I've found difficulty in penetrating really hard carbon deposits that way - the knife blade gets under them or just crushes and shatters them.

I use much the same method for cleaning cylinder heads and piston tops, but with even more care, since aluminium is easily scarred by a knife blade. (I actually use a scraper, made from an old file.) Nearly all the motor mechanics I've known have used rotary wire brushes for these jobs, though it is necessary to be gentle: a wire brush that runs across the sealing surface of an aluminium cylinder head would cause a real mess.

Thanks so much for your replies. As a complete first timer (this is the first time I have ever tried to tear down an engine and fix it (and I am enjoying it immensely) its very handy to have experienced folk help you out with stuff that seems SO obvious that the book says to do 'it' but not how.

I think I have found the problem now...bent oil rings. I think that explains the plumes of blue smoke and the plug fouling every 2 minutes.

keep those tips coming!

thanks again.
Dave

Grumpy, i think it would go without saying that you would need to be careful of the toxic fumes... hence the term "toxic". I have spent a bit on a top notch twin cartridge respirator, with some of the best cartridges for gas ect. I will use it outside in a well ventilated area. I brought the respirator because i use lots of super glue and epoxy, which if it builds up in the system it also isn't good.
I spoke to the local mower guru today and asked what he used, he said a sand blaster. He has a neat little unit in his shed the lucky bugger. I guess if you dont have a sand blaster handy the scrapping and wire brush and a bucket of elbow grease would do the trick too.

bud540, if you wear a fume mask (as distinct from a dust mask) and work outside in a well-ventilated area, I agree you are taking reasonable precautions for a home situation. (There are many industrial chemicals that can't be controlled by a fume mask, and some of them are very toxic indeed.) Sometimes we have limited options; for example used engine oil is dangerous, and most of us handle that to some extent.

I am unenthusiastic about the sand-blaster as a solution. It is difficult to keep it from affecting the sealing surfaces of the cylinder head, and of course you can't use it on the top of a piston unless the piston has been removed from the engine.

use a wire brush on the valves, and get some 2000+ grit sandpaper the finest you can get to clean around the valve seats.

I find a really small wire brush on a drill does the trick, just be careful on the alloy and around the valve seats. You dont neccecerily need to get all the carbon in my findings, just getting most of it out of the important areas (around valve seats, ports, etc) is good enough.

Thanks for all the helpful suggestions. In the end I tried a brass wire brush on a slow drill, some razor blades, and hoped for the best. Just waiting for some new rings so I can pop it back together and see how it goes.