18hp B&S intak V-twin carb problem?

12 years ago

Last week my mower was running pretty poor so I removed the carb and cleaned it. Started mowing yesterday and notice it was still running poorly.

Ran it for about 20 min then shut it off. After shutting it off I took a look to see if there was something that I missed.

I didn't see anything thing that looked off connection wise but did notice a odd thing.

One side of the intake was cold and had condensation on it...

It seemed really odd. So my question is, is this a carb problem or something else.

Thank for any help.

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Comments (9)

rcmoser
12 years ago
I'll make guess? Engine running poorly (firing on one cylinder is my guess?) Probably not firing on that cylinder. I would pull the spark plug inspect it, check gap, course plug it back in, lay it on metal part of the head, crank the engine see if you getting spark to that cylinder. if so My next move would be see if you got any compression in that cylinder.? probably not? which would next lead to Valve rocker not rocking. (most likely you push rod is bent or fell off the rocker not opening which every valve is not rocking
bte1
Original Author
12 years ago
I will check.
I will say that before cleaning the carb. I checked and adjusted the valve and checked for spark to the plug, which it had.
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bill_kapaun
12 years ago
Did you adjust the valves with the proper procedure? (1/4" past TDC)
Take the valve covers off and actually watch the AMOUNT the valves travel.
Some of these had a "soft" cam. You can compare one side to the other. Intake vs intake & exhaust vs exhaust.

You might let us know what the Model & Type numbers are.
bte1
Original Author
12 years ago
There's always a chance I missed something while adjust the valve but it is something I have done more then once with this type engine. That being said I will check the valves again.
The engine is a Model series 405700
bte1
Original Author
12 years ago
Rechecked the valves and everything looks good.
I did replace the spark plugs before I cleaned the carb, so I check to see what they looked like and did a compression test on each cylinder.
1 cylinder was at 110-115 psi, the spark plug looked pretty normal. The other cylinder was around 130 psi, the plug was pretty dry. Looked to be running lean on the side.
bill_kapaun
12 years ago
Posting the Model & Type #'s of the engine are always useful so we know which one of the dozens of briggs 18 horse engines it is.

Did you have the jets out of the carb? Many of these have a different jet between L & R cylinders.
tomplum
12 years ago
Did you catch what Bill had meant about the soft cam? A cam that has issues many times has considerably less lift on one side. So, when you crank it over watch with a ruler against the head if necessary. Usually they are not hard to spot.
bte1
Original Author
12 years ago
Just wanted to come back to let others know what the problem was.
After checking everything over again and finding nothing out of adjustment, I bought a new carb. Put it on last night, fired it up and all is running fine now.
I'm assuming there was something in the carb I just couldn't get to, to clear out.
bill_kapaun
12 years ago
"Posting the Model & Type #'s of the engine are always useful so we know which one of the dozens of briggs 18 horse engines it is.

Did you have the jets out of the carb? Many of these have a different jet between L & R cylinders."