OutdoorKing Repair Forum Forums Repairs and Maintenance Questions on Engines Questions On Honda Engines Honda GX 160 valve and running problem

I lost compression in a 5.5hp gx 160 and found it had a stuck valve( motor had been sitting awhile ) which I am guessing is the inlet valve as its on the same side as the carby,I freed it up easy enough,but now the engine won't run without the choke on?I have drained the fuel cleaned the carby etc,starts easy but shuts down as soon as you take the choke off.Am I right in saying the Inlet valve is the one closest to the carby?as I had to reset the valve clearance on that valve.Any ideas
thanks Ray

First guess would be that one valve is not closing and sealing properly. There is a possibility that you only partly unstuck the one you worked on, or the other one was sticking also, and one of them is stopping almost closed rather than completely closed. The seat may also be corroded and not sealing. Unfortunately since the engine is a Honda it presumably has the decompression device that holds one of the valves partly open until it reaches 600 rpm, so you can't easily test the compression.

You can find which valve does which which job by tracing the ports under the valves. They should be easy to see, just trace the exhaust port by continuing the exhaust pipe in the direction it's running, and seeing which valve it lines up with. It is important to know which valve is leaking - the symptom you've described sounds more like a leaky exhaust valve, but depending on circumstances it could be either valve (or both).

Did you adjust the tappet clearances accurately? A tight tappet means a leaky valve.

If the engine wants choke all the time, it is running lean, either because it has a carburetor/fuel supply fault, or because it has a leaky valve, or something else, that lets air or exhaust into the cylinder.

Thanks for that ,yea I will check the exhaust valve as well,gives me some sort of direction anyway.
Pretty confident its not a carby problem,have cleaned it out and checked float needle and seat etc.
cheers Ray

You should bear in mind that the most common cause of your symptom is an intake manifold leak or a very minor carburetor problem. You have disturbed both of those areas recently, which brings them close to the front of the list. My valve comments were based on the idea that you had not dismantled anything, and had just freed up the stuck valve by bumping the rocker arm. If the tappet clearances are correct, any sticking valve problem would fix itself with a couple of minutes running, and there is even a chance that a valve seating problem would also fix itself, so long as you were running it without load. You haven't left a vacuum hose off have you?

Grumpy,your assumption is correct and your valve comments are relevant,I did not have a problem with the motor last time I ran it,I found and freed the valve after I tried to start the motor and I lost compression and the motor was "popping" when I was trying to start it(the popping indicated a stuck valve to me)
At that stage I had not touched the carby,it was after I freed the valve that it wouldn't run without the choke,it was then that I replaced the air cleaner and and cleaned the carby.I had removed the rocker arm to free the valve.
How do you find DTC on these engines?I just done it by feel and visual and what clearance do you give the inlet and exhaust valves .006",008" ?
cheers

The owner manual for the GXV140 and GXV160K1 specifies inlet clearance 0.15 mm (0.006") cold, and exhaust 0.2 mm (0.008") cold.

I have not been able to find a mention of a timing mark in the manuals. You can find TDC approximately (within plus or minus a couple of degrees) with the pencil-in-the-sparkplug-hole trick.

It sounds from your description as if the first thing to be concerned with, is the valves and their sealing. If the valves are not closing properly you will probably find inconsistent tappet clearances, each time you run it.

Thanks ,yea I used the old screwdriver in the hole trick,when I get a chance I will go through the process again.Can't be that much wrong,starts too easy,gotta be in that inlet valve somewhere.

This is crazy,motor starts dead easy with the choke but shuts straight down when I turn it off,have been over everything again,valve clearances inlet 006" and exhaust 008",got to be something simple starts too easy,any more ideas,the hose from the OHV cover to the breather/carby assembly,whats its primary function,is it just emmission control?

The crankcase has to have a way to breathe, to allow the escape of the small amount of gas that leaks past the piston rings. The crankcase volume also varies as the piston moves up and down. There has to be a breather to accommodate all this, but for emissions control reasons, the leakage gases (known as "blow-by") are not allowed to be released into the atmosphere. The solution is to direct them into the intake pipe, so they get run through the combustion process along with the incoming clean air and fuel. The breather hose is just the way of directing surplus gas from the crankcase to the intake pipe.

How did you adjust the speed control lever? On Hondas it usually applies the choke when it is at the end of its movement, and you check this by setting the speed lever to the choke position, then pushing the control lever on top of the carburetor all the way to the right. If it was not already at its right hand stop, the choke is not being applied by the speed control when it is in the choke position, and you need to adjust the cables to make it work properly.

I haven't touched the speed control lever,I never removed the carby to clean it,only removed the bowl and breather assembly and blew it out.

It seems worthwhile checking the adjustment of the speed control lever, to make sure it really is applying full choke. If it needs full choke to run, there is something horribly wrong with the carburetor, and it will be necessary to go through the full process of checking it to find and fix that. On the other hand, if the speed control is slightly out of adjustment, it may only be necessary to go through the speed control adjustment procedure. It may be that any speed control position but "full choke" is actually operating the kill switch.

Once long, long ago I called a TV repairman because the TV suddenly had no picture at all. The repairman asked if I had recently had a visit from a small child. I said yes, immediately before the TV stopped working. Repairman smiled, walked up to the TV, and adjusted the brightness, which was down at zero. Perfect picture returned instantly. The repairman says he got a lot of those, and they were very good for his income.

mmmmmmmm what you trying to say grumpy? I fully intend to check out the speed control lever as time permits,trouble is my Mon to Fri job don't give me much tinkerin time

If it isn't the control cables, the next step involves testing for intake pipe leaks and carburetor malfunctions. That is going to be fairly complicated stuff, with a greater potential to mess the situation up so that it has to go to a mower shop in the end. That is why my process focuses on the small stuff first.