de-carbon combustion chamber

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i was reading where Briggs recommends to de-carbon the combustion chamber every 100 hours of operation. do any of our members actually perform this? could you please explain the benefits of such maintenance. i am talking in respect to briggs flatheads. would OHV engines require the same service? what is the best method of removing carbon deposits?
 
I always used a tiny dribble of water while the motor was running. You have to be very careful not to add too much water as you don't want to hydro lock the engine.

I was always told that carbon buildup in the engine combustion chamber creates "hot spots" inside the engine combustion chamber, not to mention possible valve issues, (like a chunk of carbon landing on the exhaust seat so that either the valve will not close properly or a burned valve).
 
Originally Posted By: james1950
what is the best method of removing carbon deposits?

Not letting them accumulate in the first place is the key. Run a cap full of Redline SI-1 in every tank and it will stay pretty clean.
I have been doing this with a B&S 12HP for 6 years since day 1 and the piston/chamber is nice and clean. It has well over 100 hrs.
 
If it's the low-emissions type (sidedraft carb) B&S flatheads, you don't need to de-carbon every 100hrs (more like every 500hrs or so).

These engines are known to run lean, leaner than that of plusa-ject type and for the carboning issue is very slow.

Also: if you are to consider taking off the head to decarbon, make sure you have a replacement head gasket handy.

Q.

http://www.bobistheoilguy.com/forums/ubb...476#Post2664476
 
Better than 8 bucks on a additive product to decarbon would be 8 bucks on a new head gasket and removing it with a wire brush. My 1990 8hp flathead actually stays pretty clean but my push mower doesn't. But either way 100 hours seems low to me. I assume with tightening emissions and better design the OHV engines don't need this. Actually the only flatheads they sell now are on mowers that are probably on a curb in 5 years when a plastic wheel breaks or it runs out of [never changed] oil.
 
Originally Posted By: Quest

Also: if you are to consider taking off the head to decarbon, make sure you have a replacement head gasket handy.



Yeah B&S no doubt recommends a fresh gasket once the head has been removed but in almost 50 years of working on the Briggs flatties, I've never bought a new one... With eight head bolts(as many as the average V6 per head), it simply isn't necessary...

I did have to buy one for a OHV B&S, from the standpoint of durability, no doubt a [censored] design compared to the older engines...
 
@bpepperb:

B&S is on it's very last legs RE: running their tooling and to comply with EPA stringent requirements on OPE emissions. With that most of NA no longer sells OPE flathead engines with plusa-jet carbs (non-adjustable, runs rich, etc.) They are now onto at least 625 or 675 series and upwards and couple them with Walbro clone LMS sidedraft carbs to keep up with emissions compliance.

I know B&S has ohv OPE engines out now but too new for me to acquire one and learn from them (tearing them down).

back to the subject RE: B&S flatheads: here are my 2c's worth:

(a) they do not need high octane gas for they have low compression ratio to begin with (I recall B&S site mentioned something like 73+ octane rating for their typically 7:1 compression ratio flatheads.

(b)typical combustion chamber carboning issues on B&F flatheads come from either slightly oil burning engine (oil seeps past rings into combustion chamber), engine inherently running a tad too rich (typical of pulsa-jet carb types), or rancid gasoline with lots of gum and varnish in it.


So, to keep your engine long and healthy: (a) run fresh 87octane gasoline, regardless of E10 or not; (b)for new/fresh engines, regardless of combustion chamber/head design, consider changing oil regularly (1st 5hrs, then every 20 or 25hrs); (c) change/replace/clean air filters on a regular basis.

adding fuel stabiliser such as sta-bil, etc. into gas will help in keeping the gasoline fresh longer, which, in-return, keep the combustion chamber carboning issue at-bay.

Q.
 
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