Long story short. I bought a brand new Honda 21 from Home Depot. Load it on the trailer and head to my moms to cut her grass. I was in the market for a mower anyway and researched this one. The mower said it came with oil, but it didn't. So, I hauled butt to the nearest store, got a quart of 10/30 penzoil, Grabbed funnel from the truck, and put half in. About 15-16 oz. The lawnmower didn't start until around the fourth pull and threw some smoke. It was getting dark so I had to hurry and finish it. The next day I had to cut my 1/2 acre.

This time it took about 6 pulls to start, but ran well and cut the whole thing in about 2 hours. That's when I read the manual because everyone said Hondas are great and start easy. It stated it recommends 12 oz of oil....

So did I screw it up or bend anything by putting 3-4 more oz of oil? I don't think it should've, but why the extra pulls? Then it would run fine. During my lawn cut it did bog down once due to thick grass. I stopped in place. It wanted to die and idled real slow. I stood waiting about 45 seconds and it then idled real high. Then it went back to regular idle and I continued cutting with no more problems.

Nothing on air filter or on spark plug when I checked. I drained all the oil out, put 12 oz back in and it starts on first pull now. But I swear there's a small clap or knock or like a pop noise if that makes sense. Or maybe that's just the way the Hondas sound. I have a toro recycler with Kohler and it sounds a little more smoother you could say being 4 years old. But the Honda has more power. Enlighten me please. I got the repair warranty on it.

  • Every mower I've seen has a dipstick. Use it.
    – cory
    Sep 13, 2016 at 17:48
  • I have encountered quite a few mowers and similar equipment without a dipstick. My Troy Built branded power washer with a 7.5 Briggs has three ports, and none have dipsticks. One is supposed to stick a screwdriver into one of the sump holes. Go figure. Furthermore, if one hasn't read the manual, it would be easy to overfill, if someone simply filled the sump up.
    – mongo
    Jun 3, 2019 at 18:12

2 Answers 2


I'd drain the extra few ounces out and keep running it. Doubt you hurt anything permanently. You didn't say exactly which model you bought, but assuming it is the $399 HRR 21 there is no oil pump. The vertical crank would splash the oil around more than normal but that is essentially how it lubricates anyway. The higher oil level may have pushed some oil through the breather into the air filter which if a paper element could restrict airflow somewhat and cause it to run richer than normal and/or smoke.

I'm not familiar with how the auto choke on Hondas work, but that is probably the culprit for the extra pulls getting it started. Most small engines I've seen use some form of manual heat sensing to control the choke butterfly. It's not uncommon for them to get out of adjustment, but typically more so on older mowers.


EDIT: I was mistaken when I initially read this small post on a different site, it turns out your engine is likely splash lubricated, and the engine they were comparing it to has an oil pump! As user texasranger stated, you likely did not do any permanent damage to your engine.

For future reference, I'll leave this explanation on how overfilling can hurt a motor that does use an oil pump:

Much like road cars, the 4-stroke engine in your Honda lawnmower is equipped with an oil pan at the bottom of the engine, complete with an oil pump to lubricate the various cams, journals, moving parts etc. Normally, the oil pump pulls liquid oil from the bottom of the oil pan, pumps it to the various critical locations, and gravity helps the oil find its way back into the oil pan at the bottom of the engine.

When the oil level is too high, the crankshaft will continuously slap the surface of the oil, and much like an egg beater, will whip the oil into a foam. As liquid oil continues to be pumped out of the bottom of the oil pan, it trickles down and lands on top of the foamy oil, preventing it oil from reaching the bottom of the oil pan again.

Since the oil pump is only designed to pump liquid oil rather than air, the bubbly oil eventually starves the pump. This lack of lubrication, aka oil starvation, will ruin crankshaft bearings and bearing surfaces, as well as causing a myriad of other possible problems.

  • This answer is so much better than mine that I'm thinking of removing mine...
    – anonymous2
    Sep 13, 2016 at 13:09
  • @anonymous2 Welcome to the site! Mech.SE has an enormous wealth of information. It's obvious you have an interest, and I'm excited for you to dive in and learn more. To be honest, I didn't know the answer to this question when I joined the site, but I've learned a lot, and I like to think I've taught some things as well. Since your answer contains inaccurate information I would agree that you delete it before someone down-votes, but I hope to hear more from you in the future! Thanks for contributing! Sep 13, 2016 at 14:01
  • Thanks, this is honestly the SE site I have felt the most welcome at. I do think I should point out that my answer wasn't technically incorrect, though as I thought it over, I realised it referred to a specific engine (Tecumseh) that I was working on. Of course, my memory could be failing me, too... :)
    – anonymous2
    Sep 13, 2016 at 15:31
  • 1
    An oil pump on a push mower? Unlikely. I can't help but chuckle at the irony of your lecture on giving inaccurate information.
    – cory
    Sep 13, 2016 at 17:42
  • @cory you are correct, egg on face, foot in mouth! I misread the link below. I'll edit my answer! Thank you! forums2.gardenweb.com/discussions/1501772/… Sep 13, 2016 at 18:01

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