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dljudd · Aug 13, 2009, 01:49 PM

I have a 13.5 HP Briggs and Stratton engine that "sputters", black smoke from exhaust, and gasoline splashes from the carb back into the air intake manifold. It is Model # 27B807 )or 27D807 -- hard to tell).

What could cause that?

crigby · Aug 13, 2009, 05:33 PM

Hi,
Most likely cause is the intake valve having too small a clearance or just not shutting properly for some other reason.
Black smoke because it is too rich from over-carburating, i.e. air goes through carb more than once picking up fuel each time through.
Peace,
Clarke
PS Briggs does not make a 27 cu. in. engine (first two digits.)

dljudd · Aug 13, 2009, 08:38 PM

Uh-oh. The motor is in a Craftsman mower that says 13.5 HP on the side... The first two digits of the model number of the engine is definitely 27 --(either 27B807 or 27D807), Type 0326E. Could it be that the Model # is for the valve cover? (I presume it's the valve cover that the number is stamped on. The cover is next to the spark plug.)

I suspect the valve timing may be off (key partially sheared), but maybe it's just a problem with the carb. I have had it off (nuts, then studs) to install the missing choke rod (from the throttle cable to the choke). I do suspect that the intake valve may not be closing, but by "splashing" back into the intake, I mean REALLY splashing. You can see the gasoline splashing into the intake manifold elbow (with the filter and engine cover off).

I appreciate your response, but I'm kind of at a loss, since the motor apparently doesn't exist. :confused: Any more ideas?

crigby · Aug 13, 2009, 09:05 PM

Hi,
Every number in the Briggs model means something. On a five or six digit number, those first one or two digits are the displacement. The next is a series number (or letter.) The next is the carb (there is no 800 available.) The next is the bearings in the engine ("0" means plain bearings.) The final "7" means electric start.
You can find these in any service manual for Briggs in the opening pages. It tells you how to read the numbers. There is no 27 cu. in engine built that they say; nor one with a "8" in the third digit before the end.
Peace,
Clarke

dljudd · Aug 14, 2009, 12:42 PM

Er, uh, hmmm -- excuse me -- the model is 21B807. Does that make more sense? Hope so. Maybe you still have some kind of idea...
-dj-

crigby · Aug 14, 2009, 05:24 PM

Hi,
Well, that is a valid engine. It is not a model that has been used on machines I generally see, but I did check out the parts breakdown and found one thing highly suspect. The camshaft has changed part numbers four times. One time is not unusual and would mean someone else won the bid to make it.
There is something else that can do what you describe. That is the exhaust valve not opening properly because of the cam.
Remove the sparke plug so that you may turn the engine over by hand , and remove the rocker arm cover (4 bolts.) Now slowly turn the engine clockwise while observing the movement of the rocker arms. What you are looking for is equal movement of the rocker arms as they push the valve open. If one moves very little compared to the other, it is a problem with the cam.
Peace,
Clarke