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I was given this mower about 3 years ago. When I got it, it had all sorta of issues with the transmission and deck (see my other thread), but the engine ran great. I mean it was an ad for Honda. ~13 year old engine, deck falling apart, but the engine runs like it's brand new. Engine-wise, it felt like a brand new motor. You'd start it up, it started very easily. It would almost instantly shoot up to it's operating RPM and run nice and smooth at that RPM.

But then that all changed very suddenly. Now it runs well when the choke is on, but of course at an RPM that's too low. But when you turn the choke off, it runs very rough, the RPMs bounce around. I shot a video so you could hear it first hand... then I accidentally deleted it. So stand by, I'll take and post a video about a week from now.

So the first suggestion is always that the carb might be dirty. At first I thought this was unlikely, as I almost always run sea foam in my small engine gas at 1oz per gallon. And I run a very strong ratio of sea foam to gas for maybe 1/4 a tank or so to try to really clean it out, but it made no difference. So dirt didn't seam likely. Then I happened to take the airbox off and there was no filter in there. I assume there is supposed to be an air filter on this thing right?

So is it possible that I just need to put an air filter on this thing, then run more cleaner through it till it start running well again? Or is it just a coincidence and is there likely something else entirely going on? It's been fairly well this year, but last year it got to the point where it around sputter and surge so bad with the choke OFF, that you had to keep the choke ON to use it. And with the choke on, it would run almost normally. It was enough to make me wonder if the lever/cable for the choke setting had gotten messed up some how. But it looks fine so I don't know.

Some times next week, I'll take a video and add it so you can actually hear what I'm talking about.

Running the engine without an air filter will trash the rings and cylinder walls in a hurry.

Regards

Jeff

l008com said:

Now it runs well when the choke is on, but of course at an RPM that's too low. But when you turn the choke off, it runs very rough, the RPMs bounce around.

Click to expand...

Sure sounds like a classic case of fuel flow blockage, often the main jet or emulsion tube. Try fresh fuel and a new carb (cheap, < $20) and much easier than trying to clean one.

Wow those carbs are cheap. I'll post some video this week and maybe you guys can tell me if it sounds more like dirty carb or bad piston ring. I'll also try a healthy dose of sea foam in the air intake and soak the piston for a bit, and maybe ill get lucky. And if I do, i'll also get an air filter!

Well, Cleaning the carb never hurts.
It sounds like you have a bad gasket on the intake. Maybe the plastic spacer is cracked.

Update:

Today I did the following. I started the mower up, and poured plenty of seafoam into the air intake. After it had "enough", I smothered it till it stalled out (which was surprisingly difficult!). Then I put about 3/4 of an ounce of sea foam in the oil. Then I put a brand new air filter in there! ...replacing the empty whole where an air filter was supposed to be! I let it soak for a while (while I weed-wacked), started it up, and mowed my whole lawn with it. It's a big yard so it ran for a while. I have also run lots of seafoam through the fuel this year, and the gas it's running on now is brand new gas with a 1oz per gallon dose of seafoam in it. It *may* have made a little improvement, I haven't used this mower enough lately to really be able to know for sure. But it was only after all that, that I left it running for a bit and made the video below:


This engine ran so smooth when it was given to me. It literally ran like it was brand new. I'm bummed if it's permanently damaged from not having an air filter. I had no clue it didn't have one. I'll probably do the lawn again next week, then check the oil and see if it looks particularly dirty, and if so I'll change it again (it's practically new oil, only ~2 hours on it). Maybe another week of use with cleaner in the gas and oil will do the trick, although I suspect it's not going to make a difference.

Any thoughts? Unfortunately my phone never seems to do a good job of capturing the sound of lawn mower engines.

In other news, what a difference the sharpened blades makes! It doesn't bog down at all now when you hit a big bunch of thick grass. I'll definitely be keeping my blades real sharp from now on. It was a piece of cake to sharpen on my grinding wheel.

It doesn't seem to run too bad from the vid. The only way to see if the cylinder or rings are worn is through a compression check. However Honda's have a compression release systems to aid in starting, so I'm not sure if you can perform a compression test. Anybody know how?

Regards

Jeff

I feel like the problem is a bit worse in person than it seems on the video. With the RPMs pulsing up and down a bit, and maybe a little bit of sputtering type sounds. But when I first was given this mower, the RPMs are absolutely perfect. I'd like to get it back there if I can without going crazy.

l008com said:

Update:

Today I did the following. I started the mower up, and poured plenty of seafoam into the air intake. After it had "enough", I smothered it till it stalled out (which was surprisingly difficult!). Then I put about 3/4 of an ounce of sea foam in the oil. Then I put a brand new air filter in there! ...replacing the empty whole where an air filter was supposed to be! I let it soak for a while (while I weed-wacked), started it up, and mowed my whole lawn with it. It's a big yard so it ran for a while. I have also run lots of seafoam through the fuel this year, and the gas it's running on now is brand new gas with a 1oz per gallon dose of seafoam in it. It *may* have made a little improvement, I haven't used this mower enough lately to really be able to know for sure. But it was only after all that, that I left it running for a bit and made the video below:

This engine ran so smooth when it was given to me. It literally ran like it was brand new. I'm bummed if it's permanently damaged from not having an air filter. I had no clue it didn't have one. I'll probably do the lawn again next week, then check the oil and see if it looks particularly dirty, and if so I'll change it again (it's practically new oil, only ~2 hours on it). Maybe another week of use with cleaner in the gas and oil will do the trick, although I suspect it's not going to make a difference.

Any thoughts? Unfortunately my phone never seems to do a good job of capturing the sound of lawn mower engines.

Click to expand...

First you should not use seafoam in the oil except to clean the inside of the engine just before an oil change. It thins the oil. I would replace it right away.
I noticed how you said the gas you are running now is fresh. This is probably the reason you are having hunting and surging. Honda now sales their carbs at a very low price(around $20). I think you should invest in one. Unless you have a air leak after the carb that should fix your problem. If you go to an auto parts store that sales paint you can get some paint filters that will keep your fuel clean.

Another mowing session, more sea foam in the fuel system, zero change. Is there anything left to do, or is it time to clean/rebuild the carb? It's hard to hear in the video, and much more pronounced in person, but its pulsing.

New carb was recomended to you in post number 3. At a cost of around $20 it is a no brainer.

Bought a new carb on ebay for $13.50 shipped. Put it in today. What a pain in the *** it is reassembling these carbs. The airbox cover blocks you from holding everything together and attaching the hoses! Stupid design!

But it runs perfect now, time to sell it before something else goes wrong


This is how this mower ran when I got it. So the morel of the story is: If your air filter is inside a box so you can't see it, open it up to make sure it's in there!!!

And the true end of the story... after I mowed my lawn, I was satisfied with the Mower. My chiminea was going because I wanted to burn some wood. And the old carb was sitting on the ground, covered in years of gas, oil, dirt, dust and grass. So I had the great idea of... "ill just throw this in the fire for a bit, burn off all the crap, then throw it in with my scrap metals.

Imagine my surprise when whole carb goes in, bowl comes out. Oops. Turns out the bodies are aluminum. And turns out I get my fire going really hot. That should mean there is a decent sized blob of aluminum somewhere down in the ashes. Good thing they don't make these things out of magnesium

Oh I forgot to update, I sold the mower for $100 shortly after getting it running great. Now both my old junk mowers are gone and all I have left is my awesome brand new husqvarna. Now THAT is a happy ending!