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I have a Honda HRX2172VKA lawnmower, serial number MAGA 1538656, engine serial number GJAAA-1801795 MY9*. (I include serial numbers because, as you know, many changes were made to these mowers.) I have the Honda shop manual. My wife and grandson used the mower while I was away on a 6,000 motorcycle trip so I don't know if anything in particular caused the problem when it started. It's over-revving at startup but it settles down to the correct idle speed after a couple minutes. This is an auto-choke model and I've had no problems with the choke until (possibly) now. The choke appears to be working but it never fully opens as the engine warms up. However, if I force it fully open when the mower is warmed up, the engine starts to sputter and stall. It runs fine when it's warmed up and the idle speed drops to normal and the choke is about half open.

I bent the tab slightly that the governor spring attaches to as mentioned in the manual to slow the idle speed but it over-revs again when started cold. When it's over-revving, the thottle sticks when trying to operate it manually but it works smoothly once the revs drop to normal.

Any suggestions would be greatly appreciated.

ZoneIII said:

It's over-revving at startup but it settles down to the correct idle speed after a couple minutes. This is an auto-choke model and I've had no problems with the choke until (possibly) now. The choke appears to be working but it never fully opens as the engine warms up. However, if I force it fully open when the mower is warmed up, the engine starts to sputter and stall. It runs fine when it's warmed up and the idle speed drops to normal and the choke is about half open.

I bent the tab slightly that the governor spring attaches to as mentioned in the manual to slow the idle speed but it over-revs again when started cold. When it's over-revving, the throttle sticks when trying to operate it manually but it works smoothly once the revs drop to normal.

Any suggestions would be greatly appreciated.

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Sure reads like there's some issue with air/fuel flow through the carburetor. I believe the autochoke should fully open the choke plate when the engine is warmed up. The linkage on the autochoke may be slightly binding, or there's poor heat contact on the expanding wax cylinder that activates the choke to open. On the fuel side, even the most microscopic bit of goo or debris inside the carb will cause poor running/starting issues.

Full list price for a new carb is only $20.36 (Honda Part Number 16100-Z0Y-M42). I'd be very tempted to put on a new one with new gaskets and, of course, drain out the old fuel and fill with fresh. R&R the carb will give you the chance to inspect the choke too, and ensure it is not binding or sticking in any way.

You have the shop manual...I'd try the choke troubleshooting on page 2-13... (I'll include it here for the benefit of those who may be reading this but not have a copy)

Robert,

Thanks much! I was thinking of getting a new carb and I read somewhere previously how it's surprisingly inexpensive. I think I'll do that. Thanks for the part number too. As you know, the service manual has supplements for the different models, including my mower, and I want to be sure to order the right parts. My manual is a bit different and the auto-choke troubleshooting procedure is on page 2-11 of the supplement for 217VKA model. (My manual is 61VH700E6, sixth edition.) I only mention this because there are some differences in the procedure and possibly some minor differences in parts so if someone notices differences in your page compared to their mower, that would explain it. In fact, I saw some differences in my carb with the drawings of the one the manual says I have, if I remember correctly. Anyway, I'll be sure to order the right parts and I know there are at least two versions of the auto-choke.

Thanks again!

Tom

I'm told that my mower uses carb, part number 06161-Z0y-315 which is more expensive - a little over $52. I'm not sure what the difference is as it looks the same as the one you show (above). Apparently, I have the K2 model mower and the serial number indicates my carb is the more expensive one.

ZoneIII said:

I'm told that my mower uses carb, part number 06161-Z0y-315 which is more expensive - a little over $52. I'm not sure what the difference is as it looks the same as the one you show (above). Apparently, I have the K2 model mower and the serial number indicates my carb is the more expensive one.

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I checked with our parts clerk and she tells me he '-315 part includes the carburetor and choke assembly/thermowax, while the '-M42 part is just the carburetor. There was a running change to the engine during K2 (version code) production and for whatever reason, the parts catalog calls out the '-315 as the correct carburetor to use.

Thanks again, Robert. I found that the choke is fine so I don't need the choke/thermowax. That being the case, do you think the M42 carb will work with my machine and it's choke?

What I found wrong with my mower is a real mystery to me. The choke post was on the wrong side of the choke lever. I have absolutely no idea how that happened especially because it took quite a bit of force to get it back on the right side without removing the carb (I was lazy but it worked without any problem). But the force needed to do that makes it a mystery how it got to the wrong side of the choke lever while I was away. On top of that, the little round black plastic cap on part of the choke mechanism is gone and the plastic bracket that the shut-off valve is attached to is broken although that may have happened before I was on my trip. My wife and my grandson, neither of whom know anything about lawnmowers definitely didn't take things apart. Anyway, it's a true mystery how that happened. But the choke now works fine and the engine doesn't over-rev at startup now. However, I noticed that it runs slightly rough when the air cleaner is off but smooths out perfectly when the air cleaner is installed. I'm thinking that I may have to richen the mixture slightly. I'll check that out when I mow the lawn next week. Otherwise, it's running fine now. But I still may replace the carb, if for no other reason to get one with the black plastic cap because junk may get in the mechanism it cover if I don't. At the same time, I would order a new petcock.

So, do you think the M42 carb would work with my choke mechanism? If so, I'll just order a new carb. If I have to buy the more expensive carb/choke/thermowax unit, it probably isn't worth it to me.

ZoneIII said:

So, do you think the M42 carb would work with my choke mechanism? If so, I'll just order a new carb. If I have to buy the more expensive carb/choke/thermowax unit, it probably isn't worth it to me.

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Yes, the M42 part is 'just the carb' and provided your autochoke is working properly, you don't need the more costly version that comes with the new autochoke parts.

robert@honda said:

Yes, the M42 part is 'just the carb' and provided your autochoke is working properly, you don't need the more costly version that comes with the new autochoke parts.

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Thanks again! I had almost ordered the carb/choke but, for some reason, it didn't add it to my cart so I came back to this forum to see if I got a response to my last question. You saved me a few bucks! (The choke is working perfectly now that the post is on the right side of the choke lever. It's still a total mystery how it got on that side on it's own. :confused2: The mower starts and idles fine but it lacks power and bogs down in heavy grass now. Normally, I would disassemble the carb and clean it up but since the round black cap that covers part of the choke mechanism is missing, I'll just order a new carb.

I really appreciate your help!