Need Help with a Small Engine
- Thread starter NETWizz
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What I had to do with my Honda HRN216 mower is cut the limiter cap so that it doesn't hit the limit stops anymore. They give you an adjustment range of 11:00 O'Clock to 1:00 O'Clock between the stops. The engine needs 9:00 O'Clock to idle without surging. You can see what I did by the red cut line in the picture below.
It's unlikely that cleaning will help. I (ass)umed that the pilot circuit is non adjustable, but after seeing the picture of the Honda carb, perhaps it is? If it is adjustable, then a slight adjustment is probably all that is necessary. If not and you're truly annoyed, then you'll have to remove the pilot jet and ever so slightly enlarge it (like .001" or a touch more). You'll need a small number drill bit assortment and a caliper - gauge the beginning diameter of the pilot, then figure the area of the circle (pi x Rsquared) and add 5 to 7 percent to stop the lean burble.
So it is strange because it doesn’t have the lean burble until it warms up a bit,
It actually starts up wirh no misfire at all. Then I put a loaf on it and take it off, and now it is misfiring.
Is that still carburetor or that it is lean?
So it is strange because it doesn’t have the lean burble until it warms up a bit,.
It actually starts up wirh no misfire at all. Then I put a load on it and take it off, and now it is misfiring.
Is that still carburetor or electronic?
I guess what I am asking is for help wirh making an action plan.
Should I be replacing electronic parts like a coil? Should the carb be cleaned?
I totally get what you are saying. I would use something like this:
https://www.amazon.com/Carburetor-D...cphy=9010427&hvtargid=pla-2281435177658&psc=1
First thing I pull off of every Keihin carb I install on a GCV is the limiter cap so I can tune the low speed properly. I take a soldering iron and hold it on the cap until I can pull it off with some pliers.
That is absolutely a misfire. It is not likely to be the coil, but ya never know. There are things you could try, such as making the spark plug gap quite small to reduce the electrical load on the coil. If that changes nothing, it is not the coil or plug. My guess is that the mixture is lean, and the load is so low, there is not much airflow through the cylinder. Leading to an occasional 'difficult to ignite' mix.
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It helps a little bit. The surge is never completely gone. The governor rod going to the throttle butterfly will move about once every 10 seconds at idle. When the engine is at idle under no load, the governor rod should never move. Ever.
Check the carb jets and fuel filter. Some carb jets have a tiny hole for starting, low run, high run rpms.
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Does it have the automatic choke with the thermal wax? When the wax heats up, it pushes a rod going to the choke butterfly. When the choke butterfly is closed, the engine get a limited amount of air making it run nice and rich. When the choke butterfly opens up all the way, that's when the engine will start surging. My Honda mower does the same thing.
That set may work but may skip over the size that you need. It has 15 bits in the range that THIS set has 20.
Since another member posted their Honda carb having an adjustment, I would look there first before tearing yours down and modifying
Thank you all.
I ordered a spark tester on Amazon Lisle 20610 Inline Spark Tester...
The service manual is here:
https://generatoryamaha.com.au/support/service-manuals-parts-breakdown/
Yes, I know it is NOT the USA service manual; I live in South Carolina, but it is the best I can find and most of the generator is the same aside from perhaps the power output and plugs.
The service manual calls for a YM-34487 spark tester, but for $189, Yamaha can keep it! I suspect the $12 one I ordered will do well enough, and I chose the particular one because I can get it the soonest.
Action Plan:
1. I am going to shoot a better, longer YouTube video for all of you to hear it run from cold start to warming up to misfiring. All I have to do is run a toaster... so it is NOT like you need a half-hour video.
2. I am going to test the spark and video that and post it.
3. I am going to attempt to replace the plug and verify the Gap.
4. I am going to do a carb clean despite it being a new carburetor.
5. I will post pictures of the entire carburetor, so you can help me identify the low-speed jet if applicable.
We will see if I can make any progress. This MUST be solvable either by correcting the air/fuel mixture or relacing a defective ignition component.
I ordered a spark tester on Amazon Lisle 20610 Inline Spark Tester...
The service manual is here:
https://generatoryamaha.com.au/support/service-manuals-parts-breakdown/
Yes, I know it is NOT the USA service manual; I live in South Carolina, but it is the best I can find and most of the generator is the same aside from perhaps the power output and plugs.
The service manual calls for a YM-34487 spark tester, but for $189, Yamaha can keep it! I suspect the $12 one I ordered will do well enough, and I chose the particular one because I can get it the soonest.
Action Plan:
1. I am going to shoot a better, longer YouTube video for all of you to hear it run from cold start to warming up to misfiring. All I have to do is run a toaster... so it is NOT like you need a half-hour video.
2. I am going to test the spark and video that and post it.
3. I am going to attempt to replace the plug and verify the Gap.
4. I am going to do a carb clean despite it being a new carburetor.
5. I will post pictures of the entire carburetor, so you can help me identify the low-speed jet if applicable.
We will see if I can make any progress. This MUST be solvable either by correcting the air/fuel mixture or relacing a defective ignition component.
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Holy smokes, that thing has a throttle motor assembly:
https://www.yamahapartshouse.com/oemparts/a/yam/5c4f5ba887a86609d0b4de24/carburetor
https://www.yamahapartshouse.com/oemparts/a/yam/5c4f5ba887a86609d0b4de24/carburetor
Plug a couple space heaters i to it and make another video. Sound like it's hunting for a load. My Briggs does the same thing.
Here is a bit longer video. It starts up and runs great. Then I put a load on it (toaster). After the toaster pops, it is a bit warmed up and now misfiring. The RPM meter shows it runs without hunting at first. It runs at around 3510 to 3520 RPM.
Once it starts missing, it drops appreciably to around 3450 RPM or so is about what registers with each misfire.
Once it starts missing, it drops appreciably to around 3450 RPM or so is about what registers with each misfire.
Yeah I'm with the "You need a load on it" camp, followed by the "It's too lean" one.
It's not a spark problem and don't shrink your gap. The gap they give you is the "service" one, you can actually run 0.010" wider as they consider that normal wear. If you're lean, having a wider gap gives you more of a chance to find fuel to ignite.
The answer is to monkey with the carb. Read your plugs and see what color they are. I'd work on the main jet myself TBH.
It's not a spark problem and don't shrink your gap. The gap they give you is the "service" one, you can actually run 0.010" wider as they consider that normal wear. If you're lean, having a wider gap gives you more of a chance to find fuel to ignite.
The answer is to monkey with the carb. Read your plugs and see what color they are. I'd work on the main jet myself TBH.
If its running fine under load its not electrical .
I suspect low speed jet or idle circuit.
I noticed that too, seems to be like an electronic governor. I bet it gets a signal from a load sensor to adjust throttle. I'm now thinking this may be moving the throttle butterfly into a range that causes a lean run condition. Looking at the diagram, it looks like it may be adjustable. I'm shooting in the dark because I've not ever seen one of these on a small OPE engine.
Edit: I looked at the service manual @NETWizz posted and the throttle motor does NOT appear adjustable. There is a procedure to check play in the throttle butterfly, but doesn't seem to move enough to cause a lean condition. This throttle motor is controlled by a "black box" control unit, so may be "normal" operation without a load. Not much you can do here.
I'd still try adjusting the pilot screw to see if that changes/solves the lean misfire though.
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#7 in the parts diagram from @grasscutter is the pilot screw and appears adjustable. And yes, this is where I would start at first. Quarter turn out at a time.
Otherwise it will be something to do with adjusting that throttle motor. That may be a recipe for endless adjustment disaster, as in you'll never get it right or be satisfied unless it runs really smooth. And in that case, just live with it. It's going to run under load most of the time anyway.
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