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I have a toro 21 super recycler, 1 year or so old. It has a B&S engine. There is a tube that runs from the engine to the air intake just below the filter that seems to recycle engine gasses. I notice that when the tube is connected the engine slows down. When I remove the tube the engine speeds up and runs better. My tube also seems to spew a decent amount of blue smoke and there is some oil. Surely this is not the intended design. Can anyone shed some light on what should be happening here? Surely there shouldn't be oil going into my carb with these return gases? I am running it disconnected for the time being. Mower runs better like this. My son uses this mower to mow multiple lawns a week. Also - who put that overflow on the gas tank that spills into the air filter housing. That is dumb. thanks in advance.

The tank ”overflow tube” is not an overflow tube, but a method to capture fuel vapors ob burned off, as well as a tank vent to prevent the tank from vapor locking. Government regulations. Please post the mowers model and serial numbers, I think I know the problem, but don’t want to make guesses until I know which engine you have.

serial number 1912029059623
part 125P050065F1

Thanks!

The first thing I would like you to check is the oil level. Also smell the oil, I’m thinking that you will smell gas in the oil and it will be over the full mark. If that is the case the float needle is not seating properly, allowing fuel to drain straight through the carb into the crankcase. If that is not the case, start the engine and with it running slow remove the dip stick and let it rest on top of the fill tube. It should not bounce around. It if does I suspect a blown head gasket. Post back with what you find. Please include the date of purchase and the mowers model and serial numbers.

oil was low. It is definitely blasting oil out the exhaust gas recycle tube that connects to the air intake for the carb. When I leave it disconnected there is considerable oil build up on the mower where it blows out of the tube. Oil does not smell like gas. When I undo the oil cap there is significant oil blowout, smoke and the cap bounces around because of this. The thing runs pretty well other than that. You can definitely cut a lawn with it. It was purchased second hand over a year ago.
mower model 21387
serial 406718561

If it can to me with those symptoms the first thing I would do is change the head gasket, as I’ll bet you will find that it is blown.

Watched an online video so I am an expert now on disassembly. I am taking it apart. I am no mechanic, but I am pretty sure that taking off what I think is the valve cover shouldn't spill out a bunch of oil right? It is filled with oil. There are two little rockers in there. I am removing it to get to cylinder head. Still think we had a blown head gasket? And this is allowing oil to go places it shouldn't?

Until you tell me something different, I’m still betting head gasket.

I believe you. I dug all the way in, the gasket came off in pieces and there was plenty of crust on the cylinder head and valves, etc. like maybe there was some oil cooking in the cylinder along with our gas. I guess clean it up, I have some parts cleaner, buy a new gasket and see if I can put it back together? Is there anything else I should check while I have all this apart? There is an ace hardware that deals mower parts near me. I hope they have it.

I think the gasket number is 796475, but when you get the part make sure you have your engine number with you. You can also google this part number to see if they look identical.

Changed it out last night. Cleaned everything really well. She fired right up and ran well and is still blowing a lot of smoke. I ran it about 3 -5 minutes. Runs like a champ, except for the smoke.
I am not seeing (yet) all the oil from the exhaust tube that it was previously spewing (re-breather? what do you call that thing?)
I did the test with the oil cap and it bounces around all over the place still. Lots of air pressure coming from the tube i guess?
Keep running it and see what breaks?

You have a blown head gasket.

Hi, Thanks for your reply. I just replaced the head gasket based on your previous remarks. Please read the entire thread. It posted my reply on a second page and confused me as well. Today's post is after the head gasket replacement. Is there something else that could cause the smoke? Is the smoke indicative of oil getting into the combustion chamber? Or maybe I need to run it more to burn off any remnants of parts cleaner, carbon deposits?

Did you change the oil also, as it is probably contaminated. I always do this after I replace a head gasket. It will smoke for awhile until you get all the oil out of the muffler.

"21 super recycler, 1 year or so old." It might be a little too late but isn't your mower covered for 2 years?

Good point! I think its a 2019 manufacture date, but I bought it second hand. I will look into that. Thanks!

nope. you have to have your sales receipt it says. I picked this up second hand. the trouble wasn't worth the savings.

Super Recycler units, cast deck, normally have a 5 year warranty, but depending on the dealerships in your area you probably lost your warranty by opening up the unit. Your serial number shows the unit to be either a 2015 or 2016, maybe even 2017, depending on when it was sold.

Ah. I took a look at the cylinder walls and they are scratched all to hell and back. Lots of vertical scrapes up and down the side on right and left side with pitting as well. The top and bottom of the cylinder look good. I imagine this was allowing oil past the cylinder into the combustion chamber. I think this mower is toast.

maybe I could put my honda mower engine from a machine with a worn out tranny on the toro mower?

Sounds like dirt ingestion. I doubt you will find a Honda engine to fit, because the crank lengths are different and high price.

Toro shows an 875 es engine being used,
all you need to do is measure your crank length and diameter.