Motor is wheezing, as if it's breathing - why?

It's a Honda lawnmower I'm asking about, which is about 10 years old, but
which runs fine most of the time.
I replaced the plug, ran a tank of fresh gas, and cleaned the filter, and
yet, it "wheezes" like it's breathing, normal rpm, and then slower rpm and
then normal rpm and then slower rpm and then normal rpm and then slower
rpm, etc, ad infinitum.
The interval is only about a second or two at most for this
stoichiometric:lean stoichiometric:lean stoichiometric:lean cadence to
occur and the stoichiometric:leancycles are quite regular.
The (California) carb on this thing is not adjustable (AFAIK), and the
choke shuts off in seconds as it's merely a slider that glides back in
place in a couple of seconds after initial activation.
Even after a half hour of running, the stoichiometric:lean wheezing only
gets slightly less pronounced, where the stoichiometric:lean wheezing I'm
talking about is when there is no load (e.g., it's sitting level on a
sidewalk). (Under load, it's harder to tell, but there's no "speed"
adjustment given I have the throttle bar on the handle taped tight in the
always-full-on position.)
I'm thinking it's all in the carb - i.e., choke and/or throttle...
So I guess it "could" be the throttle bar vibrating, but I don't see how;
and I guess it could be the throttle cables vibrating I guess, but again,
what can I do about that?
What could be causing this cyclic RPM change?
Reply to
Arlen Holder
Arlen Holder:
I had the same issue last year with the B&S engine on my self-propelled.
Not a 'wheezing' as I interpret it, but the up & down RPMs. Finally, it would run only while I was bent over and pressing the gas prime bulb - made mowing the lawn interesting, to say the least! :D Does yours run smoother if you hold in the primer while it is running.
My local small engine shop cleaned a lot of dirt & gummed up grime out of the carburetor and the fuel intake jets on my machine. Those fuel intakes are almost as small as the period on your screen . They can gum up easy!
Have someone take a look at that aspect of it.
Reply to
thekmanrocks
:
Thanks for hazarding advice, as I know how risky that is on the Internet.
With the exception of this four stroke push lawnmower being a California carb'd engine, they're all likely similar in many ways.
There is no primer that I know of. The only controls are the choke and the throttle, where neither is much of a control because the choke only lasts a handful of seconds (it slides back into place unless you physically block it somehow) - and the throttle is a lever on the top of the push bar where letting it go shuts off the engine (as a safety feature).
The throttle bar has been taped tightly for years.
I wouldn't even think of taking an engine in to a shop, but it might be that the carb is gummed up. The engine starts on the first pull of the cord, so it must be a 'slight' gumming of an orifice if it is.
I thought about _replacing_ the filter instead of just cleaning it, but it didn't look bad (one side had grass clippings stuck to it which I had banged off, but the inside edge was clean as brand new where it's likely a year or two old).
Given it starts right up, it can't be too badly off the stoichiometric ratio, but I do agree that the fuel jets are likely tiny. They're not adjustable as far as I know though (California rules I think).
I hate to take apart the carb if I don't have to though. That's why I asked.
Reply to
Arlen Holder
Arlen:
No squishy rubber thing down on the side of the block?
But you have in place of it a choke lever. Always hated trying to start up them 'two-slider' deals, lol! Reminds me of Dad's old flip-handle windup horror from the late '60s. He could storm n curse at that thing like you never! lol
Wind it up, flip the winder shut, jump back behind the machine, and flip the choke and throttle levers at just the right time, might fire up n run for ten seconds, "sunovabitch!" Bend over, flip open, wind. repeat. Nice way to spend a friday evening or Saturday!
But yeah, run the make and model on line, I'm sure there's an owners or service manuel for it out there. Sounds like it's perpetuallly on the verge of stalling for lack of fuel, or clean air, but you probably already checked that filter.
Reply to
thekmanrocks
Sounds like a blocked jet. On the typical non adjustable carb they are set up to run lean and draw through both the idle circuit and the main circuit to get enough fuel to run properly at full rpm. One jet starts to gum up and you get rpm surge. Two choices for repair, pull the carb, take it apart and clean it in a carb bath or ultrasonic cleaner. Or replace it with one of the hundreds of replacements out there.
You could try adding some seafoam to the fuel and see if you can clear it out that way but it really depends on just how plugged it is as to whether that will work.
Reply to
Steve W.
:
Thanks Steve W for that helpful advice.
I think it is one of those non-adjustable jets which are clogged. The engine runs, so I "can" put seafoam in, but I'm no fan of what I call "miracles in a can".
The Seafoam is likely just a trademark for a lot of stuff, mostly likely a formulation of soap for gas, aka polyetheramines, which are already in gasoline - but let me look it up...
formatting link
Hmmm... 10% to 30% alcohol wasn't expected. The petroleum distillates and hydrocarbon-based solvents were expected.
Anyway, I've never been a fan of miracles in a can, and I know you suggested it as a side note to the real problem, which is that the jets are likely clogged.
For now, since it's running, I think I'll just use a few tanks of gas and see if that cleans it out. I also might tie down the throttle cable a bit more, and ensure the throttle and choke levers aren't vibrating.
Reply to
Arlen Holder
:
Nope. Anyway, I think the answer is one of the non-adjustable jets is clogged.
What I'll do, since the mower is running, is use it for a while. Hopefully that will clean it out on its own.
Thanks for the helpful advice which I much appreciate.
Reply to
Arlen Holder
Your carb bowl is emptying at a rate faster than it is filling. It is likely full of crap. Take it apart and clean it properly. --scott
Reply to
Scott Dorsey
: >
Seafoam has been one of the few cans that I have had work in this situation. Also works very well as a top cylinder cleaner for those vehicles that get carbon build up on the pistons and rings. The ingredients may be in gasoline, but not in the concentration required to dissolve the deposits that formed from evaporation.
Now if you had a heated ultrasonic cleaner available, those do a really good job on getting them clean.
Reply to
Steve W.
:
Hi Steve W,
I appreciate your advice, where I know how risky any advice is on Usenet.
Rest assured I understand what you're saying, which is that the polyetheramines, and perhaps the alcohol and petroleum distillates in something a marketing team calls "Seafoam" are _different_ than what's in gasoline, even as they are diluted _in_ that very same gasoline.
Essentially, diluting that solution is said to turn a tank of gasoline into a tank of "carb cleaner" (and perhaps cylinder wall cleaner too!).
I get that as I'm very familiar with polyetheramines being a "soap for gas", which is why I buy only Tier 1 fuels like Costco gasoline.
The problem I have with solutions like "Techron" or "Seafoam", are that, in the end, they're merely trademarks, which are, in and of themselves, meaningless (except to a MARKETING organization).
They can put that trademark on _anything_ they want to put it on. o Yet, I understand the point - which is my jets are likely gummed up.
I agree with that point so I don't disagree with the concept that _more_ soap for gas might be better than simply using the Tier 1 Costco fuels.
In the end, I agree with everyone who suggests that my "surging" idle is likely due to a clogged jet inside the carb, which, as you noted, has mechanical solutions - but which - understandably - are more work than simply adding solvents into the fuel tank.
Reply to
Arlen Holder

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