Need help, lawn mower suddenly backfiring and no power
- Thread starter branfarm
- Start date
Pull the plug and see if it's black and sooty or white.
oilcandave also makes a good point with cam timing.
It would be nice to report back when you find the culprit.
I’m casting vote for carb. These engines are very efficient on fuel and they’ve got them tuned about as lean as it can go. The carbs are fuel sippers and precise…. ANY debris that makes it through the little crude screen in the tank cause headaches. Refueling on a dusty day can mean 3 carb-off cleanings. (Ask me how I know).
Pull the carb. It will look clean. Blow everything out you can. Take one strand from a wire brush or from stranded wire and run it up the main jet. Then add a small inline fuel filter. A model RC filter will work as long as it’s good with unleaded. Get the right size for the fuel line.
Everyone Honda engine I’ve owned has needed this… it gets dusty here in the fall.
Pull the carb. It will look clean. Blow everything out you can. Take one strand from a wire brush or from stranded wire and run it up the main jet. Then add a small inline fuel filter. A model RC filter will work as long as it’s good with unleaded. Get the right size for the fuel line.
Everyone Honda engine I’ve owned has needed this… it gets dusty here in the fall.
What carb did you replace it with? Does it have auto-choke? I've done a couple on mine and tried to source one on Amazon for convenience. It was NOT an OE Keihin and ran very poorly. Sourced a genuine OE Keihin for $22 all complete and ran like a charm. Fuel filters are critical on the GCVs as even the smallest piece of crud gets to the carb, you need a good cleaning at a minimum. With a rich condition (sounds like what you have), it could be the float is stuck or fuel needle is not shutting off fuel. Easy but messy way to check is turn on fuel valve and see if fuel keeps flowing out of carb venturi. Beyond the carb, valve clearances and timing are next to check, especially since you said over the years it has been progressively harder to start.
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Update: Thanks everyone for the tips and advice. I took the carb apart and cleaned it the best I could. After reassembling, it didn't backfire as hard (no fire coming out of the exhaust) but it still didn't sound like it was running normally. It died when I tried to engage the blade after warming up for 5 minutes.
I took the spark plug out and it's very black and sooty. I didn't have a new one on hand but I have one on order now.
I proceeded to take the valve cover off to check the clearances. The exhaust valve seemed correct using a .20mm (0.008in) gauge (fit in the gap with some drag). The intake valve was definitely out of spec though -- the .15mm (.006in) gauge wouldn't fit. I adjusted the intake side until the .15 gauge fit through with a little drag.
I didn't have any sealant on hand to replace the cover, so I added that to the order with the spark plug. Will have to wait a few days to put it back together.
I took the spark plug out and it's very black and sooty. I didn't have a new one on hand but I have one on order now.
I proceeded to take the valve cover off to check the clearances. The exhaust valve seemed correct using a .20mm (0.008in) gauge (fit in the gap with some drag). The intake valve was definitely out of spec though -- the .15mm (.006in) gauge wouldn't fit. I adjusted the intake side until the .15 gauge fit through with a little drag.
I didn't have any sealant on hand to replace the cover, so I added that to the order with the spark plug. Will have to wait a few days to put it back together.
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Had to wait until the weekend to spend time on it, but I just posted my update.
Sounds like valve clearances were pretty good. I assume the intake was just a little tight? If valves were good, it's a carb problem or timing issue. Did you check to see if the cam lobe point straight out at TDC? Timing good would mean fueling. Just save some time and get a new carburetor. Also check to see that the auto-choke is working properly, the wax actuators go out on these all the time. Could give rich fueling as the default for a bad auto-choke is closed. I get my Honda mower parts here: https://parts.shankslawn.com/oemparts
Get #s 8,12,14,19 in this parts diagram: https://parts.shankslawn.com/oempar...6612d8373287/carburetor-hrx217-k1-k2-k3-k4-k5. Get #25 if the auto-choke is not opening. Also get a high temp RTV sealant for the valve cover or it will leak. Ask me how I know.
Get #s 8,12,14,19 in this parts diagram: https://parts.shankslawn.com/oempar...6612d8373287/carburetor-hrx217-k1-k2-k3-k4-k5. Get #25 if the auto-choke is not opening. Also get a high temp RTV sealant for the valve cover or it will leak. Ask me how I know.
clearly the plug is an issue.
No, it isn't.
Over the many years I was in the OPE business and the thousands of mowers I worked on, I can count on one hand how many times the spark plug was the ACTUAL issue.
I concur with shortyb and I reiterate, I still think that you have a choke problem.
So a heavily nasty and sooty spark plug could not be an issue? I find that hard to believe. Is it the overall issue, not sure, and neither are you, but a nasty plug that is not creating good spark can absolutely be AN issue, perhaps a contributing factor.
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I didn't check for that. I'll have to find a video to explain that more (if you have a good link, please let me know).
My unit has an early serial number (in the 164XXXX range, circa 2010 ) and I don't think it has auto-choke. Can I just replace the whole carburetor assembly with a newer model?
In a single cylinder engine a bad plug will not make it run bad, it just won't run at all.
If you or anyone else doesn't want to defer to my experience, then so be it, I'll just butt-out.
Shortyb makes a valid point about the timing and he has the experience to back it up.
Check the video by @doitmyself in post #4. It give you a good idea if the timing is off just by looking at the cam lobe @ TDC.
Several GCV190s have superceded the carb to the 16100-Z0Y-M42 so possibly.
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Hey everyone, quick follow-up to let you know that my mower is back in action!
By the end of it, I'd replaced the spark plug and carburetor, adjusted the valves, and changed the oil for good measure.
Runs much better now: Honda hrx217hka after tune up (youtube.com)
(Please try to ignore all the sealant smeared over the deck -- it was a lot runnier than I expected. Hopefully that doesn't cause me problems down the road
)
Thanks again for all the tips and suggestions. Shout out to @shortyb for pointing me to the right parts.
By the end of it, I'd replaced the spark plug and carburetor, adjusted the valves, and changed the oil for good measure.
Runs much better now: Honda hrx217hka after tune up (youtube.com)
(Please try to ignore all the sealant smeared over the deck -- it was a lot runnier than I expected. Hopefully that doesn't cause me problems down the road
)Thanks again for all the tips and suggestions. Shout out to @shortyb for pointing me to the right parts.
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