# Honda GCV160 sputters, backfires, and stalls



## logoody

Just stumbled onto this forum. I have a GCV160 engine on my lawn mower, about 5 years old, has had the same problem for 4 years. The engine starts, runs about 3 minutes and then starts stumbling, backfiring, and eventually will stall out. Cutting the throttle to idle will sometimes keep the engine running, wait 15 sec and then take it up to full load, will run 5-10 minutes and then repeats the stumble. Engine stumbled when new once or twice a weekend, but wouldn't die.
If it stalls completely I have to wait 1-2 minutes before I can restart. Last weekend the engine ran perfectly, this weekend cough and sputter. I have tried flushing fuel lines, carburetor flushing/cleaning, new plug, checking keyway, magneto gap. Thought maybe some of you guru's could shed the light. Usually takes 3 or 4 pulls to start, a little smoke at startup. Seemed to stop stumbling when I held the governor open slightly to pick up the RPM for 20-30 seconds, then finished mowing about an hour.

Thanks for any help.


----------



## mitchell

*Honda*

If you have overhead valves, it is possible they are a little out of adjustment, could be an coil breaking up, but usually a coil indication, is it will run till it gets hot, the engine that is and just shut off and when cools will start right back up until it gets hot again. IF it sputtered when brand new, it is in the timing, valves, cam. Sounds like valve adjustment if you have checked everything else.


----------



## bugman

It could be valves....... the gcv should be a over head cam though....

For the coil....I've had one make the engine sputter then a few days later it started cutting out. Btw a new, well.... used spare I had fixed the situation...


----------



## scrench

See if it will run right with the fuel cap loose might not be venting


----------



## logoody

Tried the loose fuel cap bit to see if that was the problem. I thought maybe water in the fuel but I added a teaspoon of 200 proof to dry out the gas. Drained and cleaned out fuel tank. 

It is listed on the Valve cover as OHC so I'm guessing it is not pushrod. Could the cam journals be loose? In listening to the engine when it is misbehaving it sounds like the timing is jumping. I gappend the coil at 0.4mm

The engine sputters etc. the worst in the first 1-5 minutes of operation, air temperature here is a constant 65-70 deg so I can't see the overheating. But a coil breakdown is very plausible. Any way to check it? Would monitoring the spark with a timing light help to see if it was misfiring? 

Oil is clean and stays clean after changing.


----------



## mitchell

OhC, PULL THE valve cover off and see if you have pushrods and rocker arms, if you have rocker arms, and pushrods, then the rocker arms should be adjustable, you will have to put piston at top[ dead center, that is the compression stroke before it fires, insert a screw driver into spark plug hole and slowly spin engine until you feel piston come all the way to top, a shade tree trick is to plug hole with your finger until you feel compression escape, this lets you know its the compression stoke coming up before you insert screwdriver, once you find top dead center, insert your feeler gauges between valve and rocker arm, see what it reads, find out the valve settings or specs adjust the rocker nuts to tighten or loosen. Honda specs i am not sure of Briggs usually set at .003 for intake and .005 for exhaust, if wont run right by specs then its cam lobes.


----------



## Herby

logoody said:


> Just stumbled onto this forum. I have a GCV160 engine on my lawn mower, about 5 years old, has had the same problem for 4 years. The engine starts, runs about 3 minutes and then starts stumbling, backfiring, and eventually will stall out. Cutting the throttle to idle will sometimes keep the engine running, wait 15 sec and then take it up to full load, will run 5-10 minutes and then repeats the stumble. Engine stumbled when new once or twice a weekend, but wouldn't die.
> If it stalls completely I have to wait 1-2 minutes before I can restart. Last weekend the engine ran perfectly, this weekend cough and sputter. I have tried flushing fuel lines, carburetor flushing/cleaning, new plug, checking keyway, magneto gap. Thought maybe some of you guru's could shed the light. Usually takes 3 or 4 pulls to start, a little smoke at startup. Seemed to stop stumbling when I held the governor open slighty to pick up the RPM for 20-30 seconds, then finished mowing about an hour.
> 
> Thanks for any help.


 Hi, I'm Herby it is interesting that so many people have the same problem with this engine, I rebuilt two Honda GCV engines one was a GCV 135 but they are basically the same and are prone to the same problem. The 160 had a bent crankshaft so I scavenged one from another engine, the 135 had no compression so I stripped it down and found that water had entered the inlet and the valve had a layer of rust on it so that it wasn't closing properly. To start with I had the same identical problems restarting the GCV160 it started stopped sputtered backfired and so on, I was worried but having read so many threads about it I realised it was probably something simple and not the rebuild, I rechecked the timing and then removed the carb from the engine, looking at the gaskets I decided to replace with new (just in case air was entering) it had a new airfilter so that was fine. I trundled upto the top of the garden to try it out and it would not start but was backfiring and sputtering running then stopping, the only thing I hadn't done was change the spark plug, Hey presto it runs like a new born engine, sweet as a nut. I decided to ad a fuel filter after the petrol tank as I did keep finding bits floating about. In a nutshell I would in future buy a new spark plug before wasting anymore time. I bought the filter from a DIY shop for £3.00.


----------



## brianh

Thanks Herby - You saved me a swag of time - all I had to do was get the sparkplug as you suggested - Love these easy fixes.


----------



## jonbhobby

I also have been having troubles with my Honda GCV160 where the engine will stumble and then stop after a few seconds (sometimes longer). I've performed a complete carb cleaning, fuel line check, etc., etc., etc., but until I read this post today nothing helped. Very frustrating. 

All I did was run to the store and get a new spark plug and now the engine runs "like a champ". Take if from me, just go get a plug. I even went ahead and registered here just to tell my story due to the lengthy diagnostic period I had with this problem.

Thanks so much "Herby", you ROCK!


----------



## GLMARTIN

Hi folks. I read through the problems with the Honda gcv160 and think you have solved my problem. Thanks for the blog.


----------



## nolarefugee

*Bad Sparkplug*

Old post, but helped me still. Engine would run great for 30 seconds then die. 

I went through the rigamarol of cleaning carb, fuel tank, change fuel pump too. Turned out to be $3 sparkplug did the trick. 

Sometimes the things you do last should have been done first.


----------



## Viper Driver

*Try a new plug.*

Have a GCV160 on a rototiller. Had all the symptoms listed above/below. Bought a replacement spark plug for $2.19 at Advance Auto Parts. Fixed! 

I would never have believed it. For the last 50+ years have preached plugs last practically forever if you keep them cleaned and gapped. I went through most everything above figuring it was getting starved of gas since it would start on the first pull and run fine for a minute or two, then just die out and sometimes backfire. Since it ran fine during these times, I ruled out valve issues, air problems, timing, and never even considered the plug. After finding this thread, I decided to pull the plug and sure enough, it had all the signs of running extremely rich. New plug. Voila!


----------



## Milton Fox Racing

Welcome to all the new guys! Glad to have you all aboard! :cheers2:


----------



## oldhousehugger

OK So I'm new here but found the spark plug fix to be a wonderful if not total fix for my problem. After running the engine with the new plug and getting it good and hot I noticed that the magneto coil was rubbing on the flywheel, which it didn't when I set it up originally. If a magneto coil rubs on the flywheel it becomes very unhappy. I'm one of those guys who likes to set the magneto gap as narrow as possible to maximize the flux. OK so I set it to close. 
I have a theory that part of my misfire problem was due to the fact that as the flywheel heated up and expanded, the clearance I had set the magneto gap at was to small. So I triple folded my 300 wet dry paper that I had used originally and set the gap that much wider. It still makes a heck of a spark with three times the gap but runs just fine.


----------



## Kudzu

I know this is an old thread but wanted to chime in and say THANKS!! Joined just to say thanks.

Even my small engine guy missed this fix. I can rebuild a car engine but hate working on small engines. Same issue that some many talk about and my guy was stumped and assumed it was the pump (Pressure washer). 

Searching for idea and stumbled on this and the spark plug fixed the issue. So my all means try it you have the same problem!!


----------



## Milton Fox Racing

Thanks for letting us know you found the answer to your problem and then taking the time to let us know about it! 🤙 

If you have the time poke around in our sections and share any of your collections or hobby interests with us! The more the merrier!!!


----------



## opahujo

I have two problems with the Honda GCV engine on a Lawn-boy mower. The engine surges—I fixed that by thoroughly cleaning the carburetor, including the main jet and main nozzle. The second problem is that the engine misfires with little puffs of dark smoke in the exhaust when that happens. The first thing I did was replacing the spark plug with a new one—Unfortunately, unlike others here, that was of no help. 
I have been servicing Lawn-boy two-cycle mowers for over forty years and this four-cycle machine is new territory for me, I'm stumped. Could it be the coil?
I bought the mower eleven years ago and it ran great all those years.



Milton Fox Racing said:


> Thanks for letting us know you found the answer to your problem and then taking the time to let us know about it! 🤙


----------



## Milton Fox Racing

@opahujo 

What kind of fuel are you running in your Lawn Boy?


----------



## opahujo

Regular, no ethanol (Gas without ethanol is getting ever more harder to get here in the corn state of Iowa.)
I'm wondering whether I may have a sticky valve. I'm thinking about taking off the valve cover, remove the plug, crank the engine, and see whether everything moves the way it should. How does that sound? 
By the way, my Lawn-boy Model 10795 is really a Toro painted green—L-B did not use Honda engines in their four-cycle mowers.
Below my Lawn-boy mowers. The second from the left is my first one. Bought it in 1978.


----------



## Milton Fox Racing

It sounds more like you need to identify what is causing it to surge. The excess fuel when it stops surging is causing the back fire in the muffler. Since you serviced the carborator did you replace/clean the air filter as well? Clean/inspect the gas tank vent hole. Did you get any gaskets out of alignment or reuse old ones when you serviced the carborator?


----------



## opahujo

In answer to your questions:
1) I replaced the air filter.
2) I loosened the gas tank filler cap—no change. Many years ago the 8 HP engine on my snow blower kept dying. It was only in desperation that I finally tried loosening the filler cap. But sure enough, the dropping gas level was creating a negative pressure in the tank. I "modified" the cap.
3) I have replaced all gaskets, including the old one shown in the picture, with new ones.
4) Removing and then reinstalling the carburetor using the 3 1/2 inch screws can be a real challenge. It means aligning the carburetor and three other parts plus four gasket. To make that task easier, I modified two chop sticks (see image below). Using the sticks lets me stack the parts and gaskets one at a time. When done, I carefully pull out one stick and replace it with one of the long screws. Then I do the same with the other stick and screw. I have removed and reinstalled the carburetor several times and have had no problems with anything getting out of alignment.(I am sharing this in hopes it will help others faced with that task.)

Next I am going to try a new carburetor. Its a GCV 160 carburetor for pressure washers and it doesn't have the tab for the choke link. The throttle link will work OK. I want to see how the engine runs with that carburetor. Would it be OK to post the results here?


----------

