Freeing stuck intake valve Honda GCV 160 on Troy Built lawnmower

[Snagglefoot]

My neighbour's lawnmower stopped working last fall. He mentioned that if just stopped working while mowing. He brought it over. I checked the plug, drained the gas, put in new gas. Gave it a shot of starting fluid and it made a few popping sounds and and shot out bit of a flame. It definitely had very little compression. I decided to pull the valve cover. It had four bolts and I knew the valve cover is sealed sealed at the factory with black sealant. I also removed the top cover complete with the recoil assembly.

So suddenly it became a task to get the valve cover off. I removed the bolts and it was totally stuck onto the motor. I got out a hobby knife and to get more access, I pulled off the carb housing and carb, loosened the muffler cover and removed the spark plug. Using the knife I did my best to slice the seal. After that I used a large screwdriver aimed at the top corner and bottom corner and gave it a few love taps with a rubber mallet. It started coming off and then I tore the cover off by hand.

What I found is that the timing belt was still on and in good condition, but after turning the mover crank I noticed the intake valve ( closest to the intake port that the carb is bolted to), was not moving. It was stuck in the open position.

I had heard of someone on the internet with the same situation and got it loose with carb cleaner. I could see the valve stem through the intake port so I sprayed it with carb cleaner and sprayed the valve seal from the outside with liquid wrench. I then tapped on the valve a bit and after letting it sit for half an hour I gently pried on the retainer and adjacent first coil of the coil spring and it popped free. I gave it more carb cleaner inside the port and and liquid wrench on the valve seat area. I then rotated it more and both valves were working good.
I ordered a new valve cover off Amazon because the new ones have a built in guide to help keep the belt from coming off. This is explained on you tube. I'll wait for the part, use Permatex Ultra back that I have and get it back together. Stay tuned. I hope this will be useful for other GCV owners. Now for the pics.

 

[Snagglefoot]

Once I got the the valve cover off I could clearly see the valve rockers, the camshaft lobe ( black plastic), and the timing belt. I did not drain the oil so there was a bit of oil leakage into a pie plate I commandeered. Anyway, with the intake valve in the open position, it allowed the rocker arm to flop around when the cam lobe pushed on it to "open" the valve that was essentially already open. The mower was 6 years old. I might have my neighbour add some seafoam or equivalent to the gas once a year. Enjoy.

 

[ctechbob]

Check to see if the bronze guide has started walking out of the head. I had a GC series Honda that happened to and that left it with little to no compression as well. I hammered the seat back down into the head and it worked again. No idea how long it lasted as I had gotten the pressure washer free and only worked on it to sell it. Got $50 for it.

 

[satyr64]

https://www.youtube.com/watch?v=pEMgegV6sgc
maybe

 

[punisher]

The vast majority of stuck valves on GS/GC series is caused by varnished gas. Same happens on B&S late model engines as well. Happy tip, whenever you remove the valve cover on a GC engine, replace it with a GS series cover.

GS covers are nice cast aluminum vs the stamped GC covers.

 

[wag123]

Originally Posted by punisher
The vast majority of stuck valves on GS/GC series is caused by varnished gas. Same happens on B&S late model engines as well.
Yep, old/bad gas causes this. I have seen this many times on every brand of engine. Adding something to the gas doesn't solve this problem, keeping your gas fresh solves it.

 

[Zaedock]

Originally Posted by wag123
Originally Posted by punisher
The vast majority of stuck valves on GS/GC series is caused by varnished gas. Same happens on B&S late model engines as well.
Yep, old/bad gas causes this. I have seen this many times on every brand of engine. Adding something to the gas doesn't solve this problem, keeping your gas fresh solves it.


Fresh gas is always the best thing, but I don't know man, I've always used MMO in the gas of my small engine equipment. I usually add a bit of Berryman B12 too, for the first fill of the season.

I have 4 1/2 snow blowers (we call the single stage 80cc Toro half a blower), a couple push mowers, log splitter, chipper, 5HP push leaf blower, and a garden tractor and have never had a stuck valve on any of them. Does MMO help? Is it the Berryman?, I don't know. Most of my equipment is pretty old and runs great.

 

[wag123]

This ABSOLUTELY happens. If your gas is old, is orange in color, and smells like varnish, it can coat the intake valve stem with varnish when the engine is run. When the engine is shut off and cools, the varnish will harden, and if the intake valve was open when the engine was shut off, it will stick open. I have seen this MANY times over the years. It has become a bigger problem in rescent years because of the prevalence of higher compression OHV engines and their ability to burn older gas. Adding something to old/bad gas will not magically convert it to good gas, and if you use fresh gas, you will never get this kind of deposit, so you won't need to remove it. Also, topping off the old gas in your gas tank with fresh gas doesn't magically eliminate the varnish. If there is 1qt of old/bad gas in the tank and you add 1qt of fresh gas, you get 2qts of bad gas.
I'm glad that so many people ignored my advice over the years. I did a LOT of business and made a LOT of money from people who ignored my advice.

 

[JTK]

Thanks for posting this! Very cool.

I'm still rockin' my 1999 model year Honda single speed self propelled 21" with a GC engine on it. It was the first model year of the GC series. It's been my backup mower for 10yrs, but gets a beating from time to time. In fact, I just lent it out to my FIL to basically mow a hay field with given his mower is out of commission.

 

[Snagglefoot]

The valve cover I ordered came in. I adjusted the valves: 0.020 mm for the exhaust and 0.015 mm for the intake. An angled feeler gauge worked perfectly. I had to open the clearance a bit for both valves. I bought a package of Felpro gasket sheets and made a 1/8" thick rubberized cork gasket for the old cover and used it until I was sure the valve didn't stick anymore. It was a good thing since it stuck a few more times after 5 min of running each time. I added STP fuel injector cleaner to the fresh gas that was in the tank ( yes I know it's carburated). then sprayed shots of carb cleaner as it ran with the air filter off. Looks like it's good now. I cut my lawn then gave it back to my friend. I told him to use it for awhile and then I‘ll put the new cover on with RTV as per the factory. So far the rubberized cork gasket is holding. The new cover has a built in belt guide. This apparently will help keep the belt from accidentally slipping off. I also included a close up of the valve rocker arms showing the adjusting screws and lock nuts. By the way, if you elevate the front wheels while taking off the cover and adjusting the valves, it eliminates oil loss while getting the job done. Enjoy.

 

[andyd]

Fresh gas is key because E-10. I run free junk wheeled OPE. They may be old, but most just need a little cleaning and tinkering. I run MMO in all the gas and Berryman's as needed. Chem-tool is mostly acetone and lacquer thinner and it does melt varnish. I use it before I start taking the carb off. I'm about 3 for 5. MMO adds a certain je ne sais quoi that old engines like.

PS Latest rescue is gonna get a new carb, :grin2: