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Hello All,

Mower: Honda HRX217K5HYCA
So I'm having issues with my mower. It's always start at the first pull but engine is really unstable surging up and down until I stabilize the governor with my finger. After stabilizing, the engine is running smoothly and doesn't surge anymore when cold. After about 2-3 minutes, when the engine gets hot, it does fluctuate slightly and there's popping sound coming from the exhaust. Bought the mower new back in 2016; it started surging after 2 months of usage. I figured it was my fault because I put 91 octane fuel in without stabilizer and it gummed the carbs. It's the model with the blade clutch, when the blades are engaged, the engine doesn't surge so I didn't cared much for 5 mowing seasons because it's running fine when mowing. You know, first time homeowner then first kid ... you have better thing to do than repairing a small engine and the years pass...

So, I decided that this years I'll do a "big" maintenance on the thing and change the air filter, spark plug, oil (change each season), sharpen the blades and clean the carbs. I wanted to get rid of the surging.
I read thru a lot of forum and everything seems to point towards a lean mixture. I believed one of the jet may be partially blocked so I decided to clean the carbs. Pulled it from the engine, used carb cleaner put it back. Still surging. I pulled it again and cleaned it using ultrasonic batch. It's still surging.

Now, assuming I did a correct job cleaning the carb, what else can cause this?

A leaking carb gasket can cause surging.
Douse the area around the carb and engine block with wd40 from a trigger sprayer while the engine is running, if there is a change in rpm or the motor blows white smoke, leaking gasket.

If it is still surging, carb is still dirty or a fuel delivery issue. Valve adjustment would be nice too. Clean the engine block cooling fins yearly also.

slomo

slomo said:

Clean the engine block cooling fins yearly also.

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why must you clean the fins?

logert gogert said:

why must you clean the fins?

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Cooling fins, the flywheel fan blows air over them, if they get clogged enough, or just thick dust and dirt, it won't cool properly.

Scrubcadet10 said:

Cooling fins, the flywheel fan blows air over them, if they get clogged enough, or just thick dust and dirt, it won't cool properly.

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oh yea i know that, but ive never seen dirty or clogged cooling fins

logert gogert said:

oh yea i know that, but ive never seen dirty or clogged cooling fins

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But it happens.... I've pulled rats nests out of engines.... found some small animal bones in the leaves and fins one time too

Scrubcadet10 said:

But it happens.... I've pulled rats nests out of engines.... found some small animal bones in the leaves and fins one time too

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oh wait, i have experienced dirty flywheel, that mower that i got out of my neighbors yard that i was talking about, when it started for the first time, dirt hornet nests went flying everywhere!

slomo said:

Clean the engine block cooling fins yearly also.

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Thanks guys, I never cleaned the engine and now that you mention it, looks dirty and dusty.
?‍ I always thought the guys cleaning the engine was for the look ... but now that you mention it, is does make sense to keep it clean.

I'll also try checking the gasket.

if it's a GCV 160 or 190, i think there's 3 gaskets past the carb, one on the engine block, an insulator, then a gasket, then the carbn if i remember right.

It's a GCV190. There is 4 gaskets : Airbox -> Gasket -> Metal plate -> Gasket -> Carb - > Gasket ->Auto Choke > Gasket -> Engine

HazyOmega said:

Thanks guys, I never cleaned the engine and now that you mention it, looks dirty and dusty.
?‍ I always thought the guys cleaning the engine was for the look ... but now that you mention it, is does make sense to keep it clean.

I'll also try checking the gasket.

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If the fins are dirty, it stops cylinder block and head cooling. That leads to warped aluminum blocks, bores out of round, valve seats popping out, valve guides coming loose and so on. It overheats the engine. These are air and oil cooled engines. No coolant to cool them. Should be cleaned yearly or more if you bag or side sling. When you scalp in the spring, tons of dirt and grass fly airborne. The flywheel sucks all that cloud into the fin area. Older engines leak oil which attracts dirt. Grass locks onto it like mad. You are not just cleaning surface dust which you should do as well.

slomo

Make sure you clean the bottom of the cylinder too. Most engines have a side metal cover that hugs the lower cylinder block fin area. Grass and junk will get trapped in there easily.

slomo