# Honda GX31 dies out



## Rudy (Jun 14, 2006)

I have a problem where the GX31 engine on my Honda rototiller overheated. I was using the dethatching rake, and unknown to me, a lot of the thatch got blown up inside the cover for the engine, and blocked all the cooling fins. It was packed pretty solid. *sigh* I took the cover off the engine and cleaned everything out (including the fins on the flywheel), so it is breathing better now.

The engine still starts. It runs for awhile--a minute or two when cold, and maybe half a minute after it has gotten warm. But then it dies. When it dies, there is a light ticking sound from somewhere inside the engine. It will often start right back up, but then it will only run for a few seconds. 

It's not a gas problem--the bowl (primer bulb) stays full of fuel. It appears that the spark is OK, as I've taken the spark plug out and it still gets a spark. I had thought maybe it was an intermittent coil, but the ticking inside the engine is what had me concerned. The engine had fresh oil this spring, and the fuel is drained out (and the gas tank run dry) in late summer each year when I'm done using it for the year.

There is also a black plastic cap on the engine, right beneath where the spark plug screws in. It got a little melted...and in fact, it was leaking a tiny bit of oil out of the bottom. The screws were loose, probably from the plastic deforming. I tightened those up, and the leak has stopped. I don't know what the cap is for, though...there is a vent with a tube attached to it that feeds back to the air cleaner.

Any idea where to start troubleshooting, beyond what I've done? I can shoot a quick video of the engine when it's running, and you should be able to hear the ticking just before it starts. I suppose I could find a used GX31 to replace it with, but not if I can fix this one (if it's worth fixing)--the tiller has low hours on it, as I've only owned it about five years. 

I also have a Honda gas edger with the exact same engine, but I don't really want to "borrow" the engine as I use the edger twice a week. That engine still starts on the first or second pull and runs fine...and I've owned it longer.


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## rotti1968 (Apr 26, 2009)

The first thing I would do is a compression test,if that engine got hot enough to melt external plastic it more then likely has internal damage (scored piston and cylinder).cylinder compression for that engine should be 117 to 159 psi. The gx 31 is no longer, it is now the gx35. You can still get parts of the 31 with no problem but if you need to replace the engine you will get the 35 in place of .That engine lists for about 279.00 for the tiller spec.


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## Rudy (Jun 14, 2006)

I was afraid of it being something serious. I don't have a way to do a compression test, unfortunately. The slightly melted plastic piece is the "head cover". 

I did find this link for a parts catalog for the GX31:

http://hayward.arinet.com/scripts/E...frame&LoginID=hywd&loginpwd=hywd&Partner=HYWD

It shows a "crankcase set" which is probably the whole cylinder head with piston, etc. Knowing what parts cost, though, I could probably find a lightly used GX31 for the same price.

I also wonder if the valves could be sticking, which would explain the ticking noise. The only way to find out may be to tear the whole engine down...and I don't know if it's worth it. I ran it again--it ran OK, the engine speed a little unsteady, and the ticking sound happened a few times until it quit.


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## rotti1968 (Apr 26, 2009)

the crank case set does not include the piston etc. that part alone lists for 168.00
there is a complete gx 31 from a tiller on ebay right now thats in the 65.00 range as of today.


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## Rudy (Jun 14, 2006)

rotti1968 said:


> the crank case set does not include the piston etc. that part alone lists for 168.00
> there is a complete gx 31 from a tiller on ebay right now thats in the 65.00 range as of today.


I've got the GX31 on my watch list. 

I realize they have to make money on parts, but jeez--another $50 or so would get me the whole engine. Right now I'm going to have to borrow the engine from my edger to get some work done, then swap it back. 

Obviously I can't tell if the cylinder is scored, but I ran the engine again, got the ticking inside, then it quit. I am guessing the valves or valve guides are sticking ( valve stuck open, loss of compression, engine dies out). I realize anything can go wrong in an overheated engine, but I was just asking here to see if there were any common heat-related failures I should look for. 

Thanks!


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## rotti1968 (Apr 26, 2009)

the cam gear is made of a plastic material,it runs a timing belt,your valves could be seating ok when the engine is cool but as it heats they no longer seat because they expand and it shuts down. I have had a few of these apart and heat seams to be an issue for these. One recently was on the wx10 water pump and the customer was using it in to long of a up hill run and the engine over heated and wiped the piston and cylinder. Is this the honda tiller?

heres a link for a few @ small engine ware house 
http://smallenginewarehouse.com/ProductList.asp?HP=0&Category=Engine&Supplier=Honda


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## Rudy (Jun 14, 2006)

rotti1968 said:


> the cam gear is made of a plastic material,it runs a timing belt,your valves could be seating ok when the engine is cool but as it heats they no longer seat and it shuts down.


Due to the ticking sound, it almost does sound like the valve(s), like one or both are sticking. I could take off the head cover to see what's happening, but I doubt I'd see much happening in there. 



rotti1968 said:


> One recently was on the wx10 water pump and the customer was using it in to long of a up hill run and the engine over heated and wiped the piston and cylinder.


How hard is it to get at the piston and cylinder? I have the engine completely off the tiller now. (Actually, I transplanted my edger's GX31 to the tiller for now, and it's running like a champ.) Since I can't use it, I don't mind taking it apart now to see what's wrong.


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## rotti1968 (Apr 26, 2009)

For a small engine there is a quite a few things to take apart on this engine. pm me your email and ill send you a pdf of the service manual for that engine.


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## Rudy (Jun 14, 2006)

rotti1968 said:


> For a small engine there is a quite a few things to take apart on this engine. pm me your email and ill send you a pdf of the service manual for that engine.


Hey, thanks much! PM on the way. :thumbsup:


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## rotti1968 (Apr 26, 2009)

Did you get your email?


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## Rudy (Jun 14, 2006)

rotti1968 said:


> Did you get your email?


Yes I did--thanks much! I've been busy and haven't had a chance to crack it open yet.


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## rotti1968 (Apr 26, 2009)

Ok good just checking....


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## Rudy (Jun 14, 2006)

...and I still haven't had the time (or money) to work on it yet. But, I'll need to over the winter, so I can do my rototilling next spring. Thanks again for hooking me up with the information!


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## arkie6 (Jun 29, 2010)

rotti1968 said:


> For a small engine there is a quite a few things to take apart on this engine. pm me your email and ill send you a pdf of the service manual for that engine.


Is there a chance I could get a copy also? I'm having some issues with my Honda UMK431 brush cutter with the GX31 engine. Thanks. arkie6


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## m21bmr (Mar 7, 2011)

*Would like copy of GX-31 service manual*



rotti1968 said:


> For a small engine there is a quite a few things to take apart on this engine. pm me your email and ill send you a pdf of the service manual for that engine.


Could you email me a copy of this as well?
Thanks...


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## scottrogers (Apr 5, 2011)

Will post link after I have 2 posts here is 1


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## scottrogers (Apr 5, 2011)

I will post the link next


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## scottrogers (Apr 5, 2011)

Link to the manual here. Yikes why is it so hard to help people on this site. 

http://engines.honda.com/parts-and-support/owners-manuals/gx31


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