cleaning combustion chamber

Messages
30
Location
iowa
have any members noticed any benefits of removing cylinder head and cleaning out the combustion chamber deposits on a briggs flathead? i do not have a torque wrench so i may leave well enough alone.140 inch pounds is not much torque.thanks for any input.is there any way to reduce carbon deposits?
 
Messages
17,501
Location
Clovis, CA
Yes, I'll clean the top of the piston and combustion chamber from time to time. You don't need a torque wrench because the B&S flathead is not that picky. An 8-inch long 3/8'' drive ratchet is fine going by feel. Just make sure you use the proper torque sequence. I clean the top of the piston using WD-40 combined with a Dremel wire cup wheel. The trick is to keep the piston wet with WD-40 as you're running the wire wheel over it. When you see a black carbon soup over your piston, you're doing is right. Use the wire wheel on low speed. I clean the combustion chamber with the same wire cup wheel and WD-40 the same way as I clean the top of the piston. I also clean the intake and exhaust ports, but you gotta be careful not to rub the ports with the metal shroud of the wire wheel. I also stuff a little piece of Scotch-Brite in there and twist it around to help clean too. Obviously it's best to do this with the valves removed. If someone was to invent a ball shaped Scotch-Brite attachment for the Dremel, that would be perfect.
 
Messages
2,107
Location
Appleton, WI
The only time I needed to clean the combustion chamber of a flat head OPE engine was when there was too much build up that I couldn't get the mower started when it came out of winter storage. The reason it didn't start was some of the carbon shook loose when I first pulled it and jammed open a valve killing compression. I scraped the head with a mini scraper blade (0.99 at Autozone) and hit most of the top of the piston with it also being careful not to nick the bore. It fired right up. This was after 8 mowing seasons.
 
Messages
754
Location
MN
I've cleaned lots of them out on mowers, seems that people like to overfill the oil and gunk up the head pretty bad. Never used anything other than a socket, ratchet and small scraper and about 20 minutes of my time.
 
Messages
7,430
Location
beaver land EH?
http://www.bobistheoilguy.com/forums/ubbthreads.php/ubb/showflat/Number/2664444/Searchpage/1/Main/178223/Words/craftsman/Search/true/B&S_675_refresh_(past_#Post2664444 Mind you: B&S flatheads are around 7:1 compression ratio (or less), and there's really no need to go with premium fuel or similar, so long as fuel is fresh. Also note: observations not applicable to pulsa-jet types for they tend to run rich, dirty-rich (and your piston head shall always have carbon on it). Q.
 
Messages
7,430
Location
beaver land EH?
[url=http://www.bobistheoilguy.com/forums/ubbthreads.php/ubb/showflat/Number/2664444/Searchpage/1/Main/178223/Words/craftsman/Search/true/B&S_675_refresh_(past_#Post2664444][/url] let's try again. Q.
 
Messages
210
Location
WI
Originally Posted By: Merkava_4
If someone was to invent a ball shaped Scotch-Brite attachment for the Dremel, that would be perfect.
You mean like this? http://www.summitracing.com/parts/sai-260013 Standard Abrasives (3M) "Cross Buff" 8,000-20,000 RPM. If you have an adjustable speed Dremel that looks like the ticket... or use them in a die grinder, or drill.
 
Messages
5,439
Location
Ohio
You just need a wire brush (prefer brass),some carb or brake cleaner and maybe a scraper for stubborn carbon.Cover the mower deck, the brake cleaner can damage the paint. Get under the valves with the wire brush. No need to have fancy doo dads to clean it up. Obviously, use a new head gasket.
 
Messages
5,439
Location
Ohio
Originally Posted By: lars11
ok, do you always replace head gasket or could it be reused on flathead briggs etc??
They are only about 5 dollars, I replace them.Once they are compressed, I doubt you would get a perfect seal. The way they are now made, chances are you would tear it while removing the head anyway.
 
Messages
2,107
Location
Appleton, WI
I actually reused the head gasket on the Tecumseh I cleaned up. It ran just as well after the cleaning as it did when I first bought it. I just sold it to my SIL, which I wouldn't have done if I thought there would be a problem with it.
 
Messages
9,122
Location
Marshfield , MA
Yah I had a screw jam the intake valve. Long story, best left untold. Anyway, it lead to me R+R'ing the head and re-using the head gasket. I was mowing again in short order. No torque wrench. I followed the order from an old manual. It is the 11 hoss B+S I/C vertical shaft flathead on my sit down. That was 5 yrs ago. It is my main mower and used weekly in season. YMMV of course.
 

Kestas

Staff member
Messages
13,981
Location
The Motor City
I once had a no-start condition on my 2-cycle lawnboy that was traced to excessive deposits in the exhaust chamber. After a lot of scraping it came back to life. I use a measured mix -- and the problem hasn't recurred for 20 years. I'll bet the previous owner mixed by eye with way too much oil.
 
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