3 year old Briggs 3.75hp push mower ?

[little bob]

About every 3rd or 4th time I crank the mower after its been sitting several days, it will pour out blue smoke and spit oil droplets out of the muffler. The smoking will last 3-5 minutes and then stop. All the while, it runs OK. Yesterday evening it was awful. The deck below the muffler was covered in a film of oil. I frequently check and clean the air filter (foam) and keep it lightly oiled. I'm also careful not to tip it in any steep angles. Oil level is kept at full (never over full) w/30wt Chevron Supreme or NAPA and changed every 25-30 hours. Last oil change was 3 hours ago.

What's the deal? I've had several mowers like this and never had one do this regularly before.

 

[Hootbro]

Rings are not sealing on the piston and getting blow by into the combustion chamber and out the exhaust. Worn valve seat guides can also do this.

Could be worn rings and/or a poorly machined bore to begin with. This lower HP model small engines usually lack a steel sleeve bore and aluminum. Aluminum bore engines tend to have a shorter service life but not knowing your usage level per year, I cannot say if 3-4 years is too short.

Also going by the low HP rated mower, I suspect you have a entry level "box store" brand economy mower. Might be better money spent getting a new mower and better quality mower than attempting to repair this one.

 

[TFB1]

Sounds like oil level is above the cylinder which will cause smoking after a long period of setting, if you are storing it with the cylinder a little low that could be your problem... If so, there will be some oil seepage by the rings and would happen no matter how perfect the engine is... Static oil level should always be below the piston... Also a little over full could cause the same issue, don't be afraid to keep level at approx ½ way between full and add, it won't care in the least... Lastly you can try storing it with the cylinder a couple inches high(won't require much), that will keep the oil from entering the cylinder while setting...

If it still smokes at start up then possibly oil is creeping in around the valve stems, but that is unlikely... Could maybe mean the oil drain back hole in the valve spring chamber is plugged or never drilled...

 

[little bob]

Thanks. This is a Weedeater brand bought at Walmart for $150. This is its third season and it probably has about 120+/- hours on it. It runs fine and doesn't "use" any oil...just spits it out when it has one of these fits. I'll try storing it with the plug end higher and see if that helps. I dont plan to put any $ into it. I'll just get a new mower when she blows.

 

[TFB1]

If it isn't using oil, then I'd say there's a 99% chance the oil level is a little high, regardless of what the dipstick reads... As I mentioned prev, I'd start running it a little below "full" to see if that makes a difference...

 

[little bob]

Took the advise and put small flower pot under the front of the deck so the valve end was tilted up after the last two uses. No smoke or oil spitting now. Fingers crossed that this solves it. Thanks.

 

[TFB1]

Good to hear, thanks for the report...

If there is no more problem oil level is no doubt too high, I'd keep it a little low by the stick from now on...