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Discussion Starter · #1 ·
Hi all,
Lawn Mower is Husqvarna 7021P with Honda GCV160 LAO motor. I always run dry over in Summer/Fall when I don’t use it and dropped the bottom of the carb to make sure there’s no water in it. I use premium gas w/ stabilizer and has good spark plug and new air filter; oil is good. Lawn Mower always starts on one or two pulls but earlier this year developed a weird “motorboating” problem. It fluctuates between running and running max in a rhythmic interval of about twice a second. I have posted a video at youtube.


Is this a linkage issue? Has that spring failed?

thanks to all,
RSchiller
 

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Surging of the governor and RPM is almost always (99% of the time) due to a lean running condition, caused by a clogged carburetor... most likely the idle circuit is plugged, as it's a pretty small passage.
See if you can manually close the choke slowly and make the surging go away.
 

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Discussion Starter · #3 ·
Surging of the governor and RPM is almost always (99% of the time) due to a lean running condition, caused by a clogged carburetor... most likely the idle circuit is plugged, as it's a pretty small passage.
See if you can manually close the choke slowly and make the surging go away.
I think you put me on the right track. The Husqvarna has an auto choke; you pull a lever to full choke and it stays choked. When you go to start you have to pull the safety bale and then the choke lever slowly goes to full run. While the lever is still on choke or partial choke, the lawn mower is running fine. When the lever finally goes all the way to full on, then the idle-rev cycle starts. If I manually pull the choke to a partial choke the engine runs smoothly.
So based on what I've indicated, its still likely a partially clogged carb and not a defective choke system?

thank you!
 

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Discussion Starter · #7 ·
whatever works best for you and your bank account, If you buy a carb off amazon look for one sold by AllCarb or FitBest, they seem to be the better of the cheaper carbs,
Is it a clogged carb or perhaps an issue with the linkage? I speculate this as once running, if I pull the choke lever back the engine starts to die and I release. Running engine then goes back to the cycling and if I slightly pull the throttle to full, the engine does not cycle and works fine. If the carb were clogged wouldn't it sputter even if I manually pull the throttle linkage?

Rick
 

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Discussion Starter · #9 ·
Let me try to clear up; I appreciate your help. The Husqvarna 7021P has an auto-off choke system. In the first image "Choke On" the lever is pulled all the way back to full choke. It will stay there until the safety handle is engaged and then it starts to move forward and there is ample time to pull the starter. Once warmed up and running, pulling the lever back to the Choke On position will kill the motor unless it is quickly released. The 3rd image marked Spring+Lever is what I am pulling and this is evidently connect to the throttle. Once running and doing its cycling, if I pull the spring or slightly push the bottom of the vertical lever forward toward the front of the motor, the engine goes to full throttle and the cycling stops.
The spring looks good but doesn't have any tension on it and I wonder if a shorter spring would slightly pull the lever forward and solve the issue. A friend claims this motor has a governor and it is supposed to be cycling 2x/second like it is. I purchased this mower in 2017 from someone who claimed to have used it a few times and then he let ii sit with gas in the carb. The mower looked pristine and I suspected gas has gone bad clogging the jets as it wouldn't start. I got a good price, took it home and pulled the carb; the main jet was clogged. I cleaned it, put it back together and it started right up. Until earlier this year it just ran without the cycling.
My previous Honda motored lawn mower had a manual choke which I much prefer. I'll pull the air filter housing tomorrow and look further.

Thanks!!
 

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A friend claims this motor has a governor and it is supposed to be cycling 2x/second like it is.
All 4 cycles have governors and aren't supposed to surge/cycle up and down. He is wrong.

You can stop the surging by preventing the governor arm and linkage from moving, (but that doesn't fix the issues causing it) but it will still be running too lean... what's happening is, not getting enough fuel the governor senses a heavy load (since the engine slows down) the governor opens up the throttle giving more fuel (would be running too fast if it ran that far open all the time) so then it senses everything is okay and starts to close the throttle back down to normal RPM, then it senses not getting enough fuel and repeats the process. Occasionally the governor can wear and get sloppy and cause surging like this, but over the last 10 years 1 out of 500 mowers i work on for surging has been fixed with a governor adjustment...
when you pull the airfilter housing off, fire it up, and manually choke it and note what positions the choke plate is in, in the carb, when the surging stops, and then it starts to die (becomes too RICH cause of too much choke)
 

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Discussion Starter · #11 ·
I pulled the filter housing
All 4 cycles have governors and aren't supposed to surge/cycle up and down. He is wrong.

You can stop the surging by preventing the governor arm and linkage from moving, (but that doesn't fix the issues causing it) but it will still be running too lean... what's happening is, not getting enough fuel the governor senses a heavy load (since the engine slows down) the governor opens up the throttle giving more fuel (would be running too fast if it ran that far open all the time) so then it senses everything is okay and starts to close the throttle back down to normal RPM, then it senses not getting enough fuel and repeats the process. Occasionally the governor can wear and get sloppy and cause surging like this, but over the last 10 years 1 out of 500 mowers i work on for surging has been fixed with a governor adjustment...
when you pull the airfilter housing off, fire it up, and manually choke it and note what positions the choke plate is in, in the carb, when the surging stops, and then it starts to die (becomes too RICH cause of too much choke)
I pulled the filter housing but realized I would need shorter bolts to put the carb back on without the housing, insulator and gaskets to test it. I put it back together, choked it and it fired right up and the choke released properly. But I must have snagged something or done something wrong because now its running max out and pulling that back vertical throttle lever does nothing, its stuck. So I screwed up and will need to redo it. But it certainly didn't sputter ;-) Is it possible I inadvertently disconnected the governor? The throttle plate has a stop so should only have one ON position; it was running maxed out.

I also cleaned things up with rags and q-tips; too much dirt in the carb as I've had a guy come in to mow my yard and he doesn't check that the air filter is coming loose even though I zip tied it on but evidently not well enough.
Automotive tire Hood Vehicle Motor vehicle Bumper
 

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Discussion Starter · #13 ·
oooh, you're governor may have just left the building.... Try adjusting the governor first, also reassemble the carb and air filter.
View attachment 62241
Good thing you included the diagram. Yes what I was calling the vertical throttle arm is the governor arm shaft and it no longer moves. But as its right next to the overly complex linkage of the auto-off choke linkage, either the governor decided to give up the ghost right at the instance I'm working on it or more likely its user error . . . mine. And hopefully I can readjust it. It does seem to confirm your initial diagnosis that the governor was cycling the motor based on clogged jet.

Next day or two I'll have time to look at it again and need to get the short bolts so I can view when operating without the air filter housing.

Hey, I really appreciate your hanging in there with your help.
 

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Discussion Starter · #14 ·
I was able to install the carb w/o the air filter housing. Started right up but again ran max out and I noticed the governor linkage wouldn't move as I had put the carb back on too close to the engine as I placed the thick carb insulator, which goes between the engine and the carb, on the outside. Now the throttle plate and governor moved freely. Except now the darn thing won't start. Sounds like its not sparking but I doubt that; I pulled the plug and its completely dry so its not getting gas (or flooding).

I have a diagram from ereplacment parts of the gaskets and carb order but its a bit vague. Might you have a better diagram? Its a GVC160LAO S3A GJARA (Type 7). Argh . . .
 

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Discussion Starter · #15 ·
oooh, you're governor may have just left the building.... Try adjusting the governor first, also reassemble the carb and air filter.
View attachment 62241
The reason it wouldn't start with the thick insulator between the engine block and carb is that the insulator had cracked and wasn't sealing. Pulling that the engine started right up though now the throttle is wedged against the engine block again so the governor can't operate and the engine runs too hot. I'm going to superglue the insulator, reinstall and see if the sputtering is still going on. If so when I order a new insulator and just go for a new carb.

thank you Rick
 
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