OT Honda lawn mower surging part 2

INCase · Jul 19, 2021

posted this a few days ago. new post to refresh it to the top of the page. link is attached (if I did it right)

so i got a new, probably china carb from amazoooon. didn't change it one bit. not at all.

so i thought maybe these cheap things was bad to and i figured i can return it so i picked up a brand new Honda carb (only $25 from a dealer $16ish on amazoon but no time to waste) and the HONDA carb is doing the same thing. Absolutely NO change or improvement. I've check the fuel flow and it is plenty for a small engine AND if it was fuel flow i would think the bowl would be full and it would run a short time without surging before the bowl got low.

I did change the spark plug with not luck there either. new air cleaner too AND bypassed the fuel shut off and the fuel filter with a NEW direct line from the tank to the carb no improvement

is it possible the governor is goofed up and that is causing it? haven't tinkered with these much

THanks for the help.
Untitled URL Link

Janicholson · Jul 19, 2021

With the governor link to the throttle shaft lever removed, feel the governor arm motion (engine stopped) if there is any drag at all, look for a rubbing spot on the external arm/spring. If none it may be internal in the governor.
One last thing. If you run it with the air cleaner (or parts of it if the housing holds the carb on) try using your finger to close off the air intake (choke it) a little. If it just runs rough, but still surges, it is likely inside. Jim

Andy Wickiser · Jul 19, 2021

How about a weak governor spring.

SDMike · Jul 19, 2021

x2 on the governor spring either weak or broken.

Mike

Janicholson · Jul 19, 2021

A broken spring should not cause surge, it would keep the engine at idle. The spring pulls against the weights to adjust speed. A broken/weak spring does nothing. Jim

rlp in Co. · Jul 19, 2021

Does it run steady if you hold the the butterfly arm on the carb? If yes it is ignition, if no it is carb. Electronic ignition can do some strange stuff.

Bob M · Jul 19, 2021

Could also be a vacuum leak. With the engine running, try slowly closing the choke plate manually. If at some point the surging stops suspect be a vacuum leak.

Carefully check the gaskets and plastic insulator block between the carb and head for tears, cracks, etc. Or for a quick check, with the engine running play an UNLIT propane torch around the gaskets and insulator block. If this causes the engine smooth/speed up there is a leak.

MarkB_MI · Jul 20, 2021

Well, you've certainly eliminated the carb. Could there be a vacuum leak somewhere?

The governor on a small engine is pretty primitive; there's not a lot that can fail. You might be missing a spring, or have one installed incorrectly.

SDMike · Jul 20, 2021

Jim, I had a neighbor bring me a Cub Cadet push mower 2 years ago with a Honda engine, with the symptoms the OP described. I found the governor spring had come off of one end. Hooked it back up, no more surging. That is why I commented.

Mike

Geo-TH,In · Jul 20, 2021

Just because a carb is new, isn't 100% that it's good.
The after market carb I got from China, had a fuel adjustment screw.
Did the Honda carb you bought have a fuel adj screw?

OT Honda lawn mower surging part 2

INCase

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Janicholson

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Andy Wickiser

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SDMike

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Janicholson

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rlp in Co.

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Bob M

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MarkB_MI

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SDMike

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Geo-TH,In

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