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Discussion Starter · #21 ·
16166-Z8B-901 is what shows up for the GCV160LA1 S3B NH1... it's number 9 on the hondaparts carburetor diagram.

16166-Z8B-841 is the GCV190 part number for its emulsion tube... what Honda calls a Main Nozzle.

I will take a set of calipers to both and see what the actual difference is. It is interesting that the larger displacement motor has the numerically smaller emulsion tube... either the part numbers are completely arbitrary, or it is somehow referring to the outside diameter of the tube, itself.

A larger diameter emulsion tube would provide more of a restriction between the outside of the tube and the inside of the bore [where the fuel actually flows]... less fuel, smaller displacement... explains why the GCV160 has the '901 emulsion tube, and the GCV190 has the '841 main nozzle.
 

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16166-Z8B-901 is what shows up for the GCV160LA1
Is that your exact GCV160 model? There are many GCV160 models, you know...
  • GCV160 (Type A1A)(VIN# GJAE-1000001-9999999)
  • GCV160 (Type A2A)(VIN# GJAE-1000001-9999999)
  • GCV160 (Type A2R)(VIN# GJAE-1000001-9999999)
  • GCV160 (Type N1)(VIN# GJAE-1000001-9999999)
  • GCV160 (Type N2)(VIN# GJAE-1000001-9999999)
  • GCV160 (Type N7A1)(VIN# GJAE-1000001-9999999)
  • GCV160A (Type A1A)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type A1AE)(VIN# GJAEA-1000001)
  • GCV160A (Type A1AF)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type A1AS)(VIN# GJAEA-1000001)
  • GCV160A (Type A2A)(VIN# GJAEA-1000001-6699999)
  • GCV160A (Type A2R)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type A3A)(VIN# GJAEA-1000001-6699999)
  • GCV160A (Type BHH)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type E1A2)(VIN# GJAEA-8000001-8018819)
  • GCV160A (Type E1A4)(VIN# GJAEA-8000001-8018819)
  • GCV160A (Type E1G7)(VIN# GJAEA-8000001-8018819)
  • GCV160A (Type E5A4)(VIN# GJAEA-8000001-8018819)
  • GCV160A (Type EHHB)(VIN# GJAEA-8000001-8018819)
  • GCV160A (Type N1A)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type N1AF)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type N5A)(VIN# GJAEA-1000001)
  • GCV160A (Type N5AF)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type N5MF)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type N5R)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type N7A1)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type NBL1)(VIN# GJAEA-1000001)
  • GCV160A (Type R1A)(VIN# GJAEA-8000001-8018819)
  • GCV160A (Type R3A)(VIN# GJAEA-8000001-8018819)
  • GCV160A (Type R3A1)(VIN# GJAEA-8000001-8018819)
  • GCV160A (Type RTL1)(VIN# GJAEA-1000001)
  • GCV160A (Type S1A)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type S1A1)(VIN# GJAEA-1000001-6699999)
  • GCV160A (Type S1M)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type S3A)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type S3A2)(VIN# GJAEA-1000001)
  • GCV160A (Type S3H)(VIN# GJAEA-1000001-5386302)
  • GCV160A (Type STA1)(VIN# GJAEA-1000001-6699999)
  • GCV160A (Type STL1)(VIN# GJAEA-1000001)
  • GCV160LA (Type A1A)(VIN# GJAEA-5386303)
  • GCV160LA (Type A1AF)(VIN# GJAEA-5386303)
  • GCV160LA (Type A2R)(VIN# GJAEA-5386303)
  • GCV160LA (Type E1A2)(VIN# GJAEA-8018820)
  • GCV160LA (Type N1AF)(VIN# GJAEA-5386303)
  • GCV160LA (Type BHH)(VIN# GJAEA-5386303)
  • GCV160LA (Type E1A2)(VIN# GJAEA-8018820)
  • GCV160LA (Type E1A2)(VIN# GJAEA-8018820)
  • GCV160LA (Type N1A)(VIN# GJAEA-5386303)
  • GCV160LA (Type N1AF)(VIN# GJAEA-5386303)
  • GCV160LA (Type N1AF)(VIN# GJAEA-5386303)
  • GCV160LA (Type N5AF)(VIN# GJAEA-5386303)
  • GCV160LA (Type N5AF)(VIN# GJAEA-5386303)
  • GCV160LA (Type N5MF)(VIN# GJAEA-5386303)
  • GCV160LA (Type N5MF)(VIN# GJAEA-5386303)
  • GCV160LA (Type N5R)(VIN# GJAEA-5386303)
  • GCV160LA (Type N5R)(VIN# GJAEA-5386303)
  • GCV160LA (Type N7A1)(VIN# GJAEA-5386303)
  • GCV160LA (Type N7A1)(VIN# GJAEA-5386303)
  • GCV160LA (Type N7S1)(VIN# GJAEA-5386303)
  • GCV160LA (Type N7S1)(VIN# GJAEA-5386303)
  • GCV160LA (Type R3A)(VIN# GJAEA-8018820)
  • GCV160LA (Type R3A)(VIN# GJAEA-8018820)
  • GCV160LA (Type S1A)(VIN# GJAEA-5386303)
  • GCV160LA (Type S1A)(VIN# GJAEA-5386303)
  • GCV160LA (Type S1M)(VIN# GJAEA-5386303)
  • GCV160LA (Type S1M)(VIN# GJAEA-5386303)
  • GCV160LA (Type S3A)(VIN# GJAEA-5386303)
  • GCV160LA (Type S3A)(VIN# GJAEA-5386303)
  • GCV160LA (Type S3H)(VIN# GJAEA-5386303)
  • GCV160LA (Type S3H)(VIN# GJAEA-5386303)
  • GCV160LA0 (Type A1A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type A1A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type A1AF)(VIN# GJARA-1000001)
  • GCV160LA0 (Type A1AF)(VIN# GJARA-1000001)
  • GCV160LA0 (Type A2R)(VIN# GJARA-1000001)
  • GCV160LA0 (Type A2R)(VIN# GJARA-1000001)
  • GCV160LA0 (Type BHH)(VIN# GJARA-1000001)
  • GCV160LA0 (Type BHH)(VIN# GJARA-1000001)
  • GCV160LA0 (Type E1A2)(VIN# GJARA-1000001)
  • GCV160LA0 (Type E1A2)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N1A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N1A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N1AF)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N1AF)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N5AF)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N5AF)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N5MF)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N5MF)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N5R)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N5R)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N5RB)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N5RB)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N7A1)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N7A1)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N7S1)(VIN# GJARA-1000001)
  • GCV160LA0 (Type N7S1)(VIN# GJARA-1000001)
  • GCV160LA0 (Type R3A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type R3A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S1A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S1A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S1M)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S1M)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S3A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S3A)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S3H)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S3H)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S3T)(VIN# GJARA-1000001)
  • GCV160LA0 (Type S3T)(VIN# GJARA-1000001)
  • GCV160LA0 (Type SBT)(VIN# GJARA-1000001)
  • GCV160LA0 (Type SBT)(VIN# GJARA-1000001)
  • GCV160LE (Type A2A9)(VIN# GJAAE-1000001)
  • GCV160LE (Type A2A9)(VIN# GJAAE-1000001)
  • GCV160LE (Type A4A9)(VIN# GJAAE-1000001)
  • GCV160LE (Type A4A9)(VIN# GJAAE-1000001)
  • GCV160LE (Type A7H1)(VIN# GJAAE-1000001)
  • GCV160LE (Type A7H1)(VIN# GJAAE-1000001)
  • GCV160LE (Type N7A1)(VIN# GJAAE-1000001)
  • GCV160LE (Type N7A1)(VIN# GJAAE-1000001)
 

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Discussion Starter · #23 ·
Yeah, GCV160LA1 S3B NH1 is on the barcode sticker on the back. It's on a Craftsman M250 push mower, if that means anything.

Did Honda actually put a closed loop PCV system on the GCV's? The breather tube appears to lead to a bowl inside the air box... to feed crankcase oil vapor back into the combustion chamber, I suppose.

Does the carb/intake actually provide vacuum to pull crankcase gas through this system?

Could one simply put a valve cover PCV filter in place of the breather tube? Assuming that it doesn't interfere with the throttle linkage? I cannot guarantee the factory air box and filter will continue to be used, so this breather system may need to change, as well.
 

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Discussion Starter · #25 ·
I figured as much. Thank you.

I'm seriously considering running a little conical dirtbike airfilter, and thought it would be pretty slick to have a matching, although smaller, conical filter next to it on the breather. If I am feeling squirrelly, I could even possibly modify a crankcase breather cover with a valve cover breather kit.

By the looks of it, the breather hose is just inserted through a hole in the breather cover, and is left unsecured inside.
 

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Discussion Starter · #26 ·
The Honda/Keihin "constant velocity" carb is an interesting piece to use on a lawn mower, me-thinks.

It [the Constant Velocity Keihin carb] has an emulsion tube, which is something Weber has developed extensively to modify fuel curves... generally to provide mid-range adjustments. A lawn mower has no mid-range to adjust.

And this is not the same CVK casting/body used on dirt bikes, so to carry over that emulsion tube has to be for some economy/emissions gain. My only assumption being that literally any measurable emulsion allows smaller jets to be used, overall. I wonder if Weber emulsion tubes fit... that would be neat.

Has anyone bother re-jetting their push mower carb? Particularly a GCV160/190 carb?

The demand of a 160cc engine @ 3500rpms is similar to that of a 70cc engine @ 8500rpms... and such engines are using #80 main jets, #40 pilots. The GCV160 has a #55 main jet from the factory. The GCV190 has a #65, for reference. Both the GCV main jets seem on the lean side.

I have already ordered the #65 main jet for my GCV160, which still seems to be leaving very little margin of error, all things considered... especially if I plan on turning up said GCV160 to ~3600rpms.

Would a richer main jet, something like a #80, have any sort of cooling effect? Every little bit helps with an air cooled engine (especially one without an oil pump/cooler).
 

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Discussion Starter · #27 ·
To answer my own question, yes. You can jet the carb rich to effectively make the engine run cooler... this process is used quite a bit in aviation as well as 2-stroke dirt bikes, and is called "rich of peak".

In this regard, I may very well order a 080 main jet to try. Honda has 99101-124-xxx main jets ranging from #48 to #150, so we have options. I have found #35, #38, #40, and #45 pilot jets, and can only assume there is also a #42 available, too [although I didn't bother searching for it]. And three different emulsion tubes available, but their differences remain a mystery to me. There are quite a few different CVK adjustable fuel mixture screws out there... I hope I can find one that works, although it really isn't the end of the world if I cannot.

It is just a push mower, not a pit bike...
 

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The Federal Government set the engine RPM specification according to the length of the cutting blade for operator safety. It is called "Blade tip speed". A discussion can be found here what blade tip speed | Lawn Mower Forum and more info doing a Google search, if your interested. The blade is a highly rotating piece of steel that can cause severe injuries or death if pushed beyond it's limits. As you said, it is just a push mower, not a pit bike.
 

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Discussion Starter · #29 ·
Interesting... it would appear ~3500rpms is about as fast as I can go with a 21" blade... according to the "revised" standard of 19,000fpm. A 21" blade could be spun to ~3800rpms using the old standard of 21,000fpm. Not sure if the blades are actually made any different between the two different sets of standards, or how significant that 2,000fpm difference really is.

Something being flung out the chute is going to hurt, either way, but I doubt the difference is truly that significant. Blade harmonics might be a factor, but even cheap manufacturering and metalurgy processes today probably produce better blades, overall, than when the standards allowed higher tip speeds.

Who actually even knows which tests were used to establish or revise these standards, anyways? They could be completely arbitraty BS numbers established so insurance companies have an excuse not to pay.
 

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Discussion Starter · #30 ·
In the name of science, would increasing just the pilot jet size enrich the entire rpm/throttle position spectrum?

Pretty sure the idle circuit is always contributing fuel, and I was wondering to what extent does the pilot jet affect full throttle enrichment?
 

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Discussion Starter · #31 ·
Meh, found an answer to my own question...

It appears that a typical idle circuit only contributes about 15% [at most] of the overall fuel during full throttle.

So, huge changes in pilot size (~30%) amount to quite small (~4%) changes in overall fuel at WOT... not at all a significant amount of tuning available from messing with pilot jets, alone. I doubt one would even able to notice a difference at full throttle without equipment specifically designed to detect minor changes in AFR... it MIGHT be detectable with EGT sensors, but I doubt it.
 

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Discussion Starter · #32 ·
Would there be any benefits to adding Honda's little vacuum powered fuel pump to a lawn mower? The 16700-z0j-003 pump appears to be standard on some other GC160/GC190 models, as well as GX engines.

Although it provides yet another component that could potentially fail, I am relatively confident in the simplicity of the mechanism to last for what I would be asking of it. I could even isolate the pump, itself, from vibration with a creative mount utizing rubber or polymer spacers... if such measures might be remotely necessary. The generators that use them do not seem to go through such efforts to protect the pump from vibrations.

Again, I don't know if there would be any benefits... other than possibly guaranteed fuel supply on ridiculous sidehill runs? Pick a different approach. Lol. And, if the whole mower is that tilted, the pickup location of the tank could be above the level of the fuel in the tank, and no pump is going to solve that.

Would there possibly be any drawbacks associated with installing a vacuum operated fuel pump?

It's not like that vacuum signal ahead of the ventruri/butterfly is being used for anything else... nor will tapping the intake to access that vacuum signal weaken or otherwise affect the function of the carburetor downstream. So, I don't see anything wrong with delivering an ever so slightly more consistent supply of fuel... obviously the vacuum operated pump does not overpower the float/needle, given that this exact pump is mounted on various other models within the same family of engines that I am tinkering with.
 
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