[RiffRaff]

Hello,

I have a Yard Machines Riding Lawn Mower with a 16.5 HP Briggs and Stratton Single Cylinder OHV that is filling the crankcase with fuel, gasoline.

This happens within an hour of mowing. I have dumped the oil twice now and it fills the crankcase within an hour of operation.

It is not blowing smoke out the exhaust, however I did notice that a small amount of oil is dripping from (as far as I can tell so far) the valve cover gasket. It is a pretty small amount and would have not noticed except that is is dripping onto the muffler.

Last year I had the head gasket replaced as it was blown in the thin section that runs past the valve area. Apparently a known problem with these engines. The repair shop told me the new gasket has been improved in this area.

I really can't justify sinking a bunch more money into this rider since it is about 9 years old and these Wal-Mart special's just don't seem to stand the test of time well at all.

Is my head gasket leaking again, in a new area? Or is this a carb/float/needle problem?

Thanks for any advice

[shelby19]

What's happening is as the engine warms up, the jug that the piston slides up and down in, has a crack in it so it spreads open, so gas is intering the oil where the crack is loacated. Best way to find it is to take it off, let it sit outside for a couple of days, there will be rust where the crack is.[ when alumium heats up it expands]

[MOWERMAN2468]

The problem lies within the carb. Your needle and float are staying in the down (fill) position and flooding the carb. The gas then floods the carb bowl and has nowhere else to go except out the other side of the carb. Through the intake, seeps past the intake valve and then seeps past the piston rings. Then finally into the crankcase.
Remove the carb and inspect, replace parts as needed. Installing an inline fuel shutoff will help to remedy this problem. But the shutoff only helps prevent this problem if it is used each time you shut the engine off.

[MOWERMAN2468]

Whats happening is as the engine warms up, the jug that the piston slides up and down in, has a crack in it so it spreads open, so gas is intering the oil where the crack is loacated. Best way to find it is to take it off, let it sit outside for a couple of days, there will be rust where the crack is.[ when alumium heats up it expands]

How many times have you saw ALUMINUM rust?? The piston is aluminum. And the problem is going to be found in the carb.

[leonardbonamo]

Totally true. My 14.5 HP Briggs did same after sitting up. I knew instantly it had to be float needle stuck. It had gelled up ethanol residue and a little piece of bowl gasket stuck right on the rubber tip. So even if it wasn't gunked up, it would seep past the float needle seal. I cleaned it and sprayed carb cleaner through all the jets/orifices including mixture screw. Drained crankcase, and refilled with fresh oil. It fired right up and I mowed the lawn. Only problem is that after about 15 minutes, the motor bogged down, and lost power. I adjusted the valves prior to all of this and I think an adjuster broke off and vibrated loose. I probably have a valve not opening due to loose rocker arm. I was frustrated, and just parked it to let it cool down. I will take the valve cover off again and inspect.

If it ain't one thing it is another. I had just put a new solenoid on it at the end of last season. Then learned about too much valve lash not releasing compression as it was cranking/running 3 thousanths, versus 10 - 12 thousanths clearance it had after 15 years of operation. I still had starter problem. I removed the starter, and connected it to 12 volts, it would hardly turn. I took the bottom cover off the starter and found that the rotor shaft bushing was all gunked up and rust from rotor shaft had hardened up. I cleaned it all up and reassembled it. It spun freely when 12 volts was applied. I reinstalled it and it started the mower, but the clutch drive and starter drive gear hung up and they but dissentegrated. I bought a comple starter drive rebuild kit and installed it. The starter works perfectly now, but the solenoid was again destroyed in the process of figuring out the high compression during starting coupled with nseized up rotoer shaft.

Will see how it goes when I check rocker arm/valve lash adjusters. Have read of other folks breaking these adjusters. They pop apart after you tighten them (too much I assume) and shoot across the garage with a tink sound. I will soldier onward...

Have another old rider I tinker with a keep running (changed old worn out 38" deck with 42" apparently older '97 murray 38, 40 and 42" decks are interchangeable. Little 12.5 HP B&S still haqs plenty of power and pulls my 290 lb butt around with power to spare. Also have a brand new 20 HP 46" Ariens. It is a cadillac, but I can't give up on the old '94 Wizard 42" and Muuray. I am a tinkerer by nature, since age 10.

Leonard Bonamo

[farmboy59]

I have a Murray Victa riding mower with a B&S 16.5 hp /OHV engine this is the second one I have purchased this engine was mfg. in 1999 it was running fine yesterday today it is blowing black smoke and mis firing bad,I put a new spark plug in it thinking that's was the problem,but that didn't change anything now I have black soot and oil on the plug ,could it have a broken oil ring,and do they sell engine rebuild kits. Please help.

[DG]

Check your oil and see if it has gas in it.
If so needs carb needle and seat.