Honda FG100 tiller w/ dirty GX31 engine & oil

redeyedgreenmanApril 29, 2009

Greetings to all helpful gurus of small engine repair,

having issues with a:

- Honda Harmony FG100 mini-tiller;

- with Honda GX31 4-stroke engine; dirty/grey oil, filthy/leaky motor.

(fyi: my mechanical ability = life long bmx & mt bike mechanic, minor automobile work, basic tune-up replacement items & replaced a couple starters,.. so not much)

it belongs to my girlfriends family, and they've been passing it around and sharing it for about 5 years, without anyone reading the owners manual, or anyone performing any maintaince on it. she just got it back from her brother, and started it a few days ago, with much smoking from the engine. i went out and checked it out, to find the motor oil was very grey and looked to maybe have some water in it. (perhaps at some point someone left it out in the rain, ?and water got in through the air cleaner sponge??) ive gathered from reading some discussions here, that the grey oil is from metal filings, caused from the air filter being dirty, and letting debris into the motor/ pistons.

-so i dumped the dirty oil out, and rinsed it a few times with some fresh motor oil, topped it off w/ fresh oil. i didnt wash the sponge filter, but wrang out all the nasty oil from it, an put some fresh oil on it, and re-wrang it out a couple times.

- started it again, ran it for a couple of minutes, still very smokey, but not quite as bad as before. then i checked the (new)oil, and looked about as bad as before after only running for a moment.

now i'm not fammilar with this machine/motor, and hadnt read the owners manual by this point either. i noticed the motor seemed to be leaking/pumping quite a bit of oil into the air filter chamber, and leaking out from there. (not sure if that is because i might have tipped it over, onto a side that youre not supposed to. also when i was rinising out the dirty oil, with a few ounces of clean,.. i was turning it every which way, then dumping.)

- i decided at this point the engine needed a major cleaning, before being run again, ALSO NOTING THAT THE ENGINE WAS EVERYWHERE FILTHY WITH MUD/OIL MIXTURE, so much so, that couldnt determine the place(s) where it might be leaking from.

- then i got hold of the owners manual online, and started reading some of the forum discussions on this unit. got myself a grease gun, figuring no-one has yet checked on the transmission unit grease level. ?im wondering if i should open that up and give it a thorough cleaning, and maybe replace the parts that typically fail if they look worn?? or just just top it off with new grease and hope for the best and wait for its inevitable breakdown??

- then i started tearing the motor down, and cleaning with carbureator-cleaner spray solvent. i dont have the "shop/repair manual", so in this endeavor i am getting to the limits of mechanical agility, and lacking in the appropriate technical language. i removed all the exterior fixtures from the motor: muffler, carbureator, manifolds, plates, 'oil outlet valve cover', etc. this allowed me access to the inner motor from a few places to spray with the carb cleaner.

so at this point i'm ready to order/purchase the 3 gaskets i encountered, and put it back together with a new spark plug, and a cleaned air filter. without a service manual, i'm not comfortable tearing it down any more to give it a complete cleaning, and i dont have a lot of tools here,.. no timing gun or anything particuar like that, that might be required.

?i'm wondering if i should throw it back together and hope for the best, and once its running again, i'll be able to see where it might have some leakage. or do you think it needs to be taken to a professional, for a total overhaul & cleaning,.. considering the grey oil & possible piston/engine damage??


- any suggestions for cleaning out the interior of the motor, aside from the carb cleaner? how about using my shop vac as a compressed air blower, to blow/suck any particles out?

- are petes & plano, best/cheapest source for gaskets or gasket kit? and throttle cable too.

glad i found this forum and the expert transmission info for this unit. thanks for any advice, and heaven knows i can stand to score some honey-dew points with my gal, ...and mother in law ;~) lol.

cheers, matt

found this forum searching:

[honda, harmony OR tiller, FG100 OR GX31 OR "FG 100" OR "GX 31"]

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I think i'd just take it back, and forget it! If the owners cared so little about it, you shouldn't get involved with it, because anything that happens now will be your fault! Take this bit of wisdom from an old experienced person, who has had his share of disrespected engines dumped in his lap, by those who think everything will run forever, with minimum care!

    Bookmark   April 29, 2009 at 8:45PM
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Make sure you don't overfill the oil. You are supposed to turn it on it's side and remove the oil stick--but if you look at the manual, "side" is more like the front. If overfilled, oil will pour out of the filter area and you will have smoking. Not sure what to make of the muddy oil after the recent oil change.

    Bookmark   April 29, 2009 at 10:28PM
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Well, as suggested over filling could cause the smoke? I would check the compression, Probably wore out from lack of pre-ventive routine maintenance like you mentioned, oil not being changed, air cleaner not being cleaned or replaced, ect.... I am suprised you can get it to run period. But, IMO you got to know the condition of the combustion chamber (piston to bore clearnance, rings) I would also wash out the comb chamber with spray carb cleaner and pull rope with the spark plug removed (this will clean all the oil and may loosen up any carbon that maybe causing the rings to stick causing smoke).

With all that hasn't been done I would be amazed if it's not worn out ( causing blow by combustion gas to pressurize the vent system thus getting the oil in the air cleaner and smoke). another thing you need to concentrate you cleaning efforts on the inside and don't worry about the cosmetic's on the outside, you can make it look new, but that don't mean it going to run like new. For that it's all about the inside.

With all that said it maybe wise to listen to rustj and just not get involved cause three things could happen as he mentioned two (being bad) and third being you fix it and now they will all seek your help when they have any little problem. Which could be bad also???????????????

    Bookmark   April 30, 2009 at 6:01PM
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jonas302(central mn 4)

I would think its water or condensation in the oil its very hard to clean out by just dumping the oil use some seafaom in the oil and run it then change it until clean

    Bookmark   May 2, 2009 at 10:14PM
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thanks for the suggestions, sorry i'm slow to reply, been on the run the last several days:

>>> rcmoser wrote:
I would check the compression, Probably wore out from lack of pre-ventive routine maintenance like you mentioned, oil not being changed, air cleaner not being cleaned or replaced, ect.... I am suprised you can get it to run period. But, IMO you got to know the condition of the combustion chamber (piston to bore clearnance, rings) so do you think it would be best to take it for an engine rebuild? can you replace the damaged pistons parts on these engines?,.. and if so how much would it roughly cost to have someone do this, assuming that all replaceable parts need/&get replaced??

if i dont end up taking it into the shop for a rebuild, i' guess i'll try rinseing it out a few times with some dry-gas water removing treatment, and throw another can of carb spray at the internal chambers,.. then try the seafoam once it gets up and running.

grandma-in-law couldnt wait to get her garden tilled so she went out and bought a P.O.S 31cc 2-stroke tiller from lowes for $200. i had told her to get a fullsize tiller, as our yard is a farm/jungle at the bottom of a canyon drainage. it worked fine for her little garden plot, but didnt make it 5 feet through the 'secondary succession' experiment that is our garden. so now i have a minnie mouse tiller, and a defunct mickey mouse tiller at my disposal, and feeling goofy with these infernal combustion engines.

thanks again for the advice,.. matt

    Bookmark   May 5, 2009 at 3:29PM
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I don't know about the rest of the tiller, but I do know something about the GX31.
The Honda small engines can run at all position BUT it can't sit on the side or up side down!!!!! VERY IMPORTANT!!!. It has a oil chamber to whip the oil into mist so you can run in all position. But when the engine stop, oil is going to go to the lowest level due to gravity. If the engine sit side way or up side down, oil will sip through the rings and go into the combussion chamber. If you leave it sit long enough, the engine not only hard to start, also it will smoke for a while. But it will clear up. That is the reason the foam filter soak with oil.

So do not just tear the engine up until you run more test. You might want to clean the carb. I just did one on my GX31 and is not that hard. But If you can start the engine, I don't think you even need to do that. Just wash the foam filter with soap and water, put oil and put it back. Change the gas filter and check the plug. You check the oil but putting the engine with cylinder upwards, on flat level. Remove the drain plug and make sure the oil just not overflow.

Start and let it run for a little while, the smoke should clear up. Then you can continue testing whether it has power. I am not saying the engine has no problem, just say the smoking is normal if the engine sit in wrong position.

    Bookmark   May 5, 2009 at 8:13PM
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Me Bad!! I filled my Honda Harmony FG100 with oil with the left side down! Heard girggling but filled it up anyway. I let it sit upright while I went for parts, a new gas primer bulb thing (I'm not a mechanic), new fuel line and air filter. When I came back to the tiller the next day, oil was dripping out through the air filter! It was soaked. So, I checked the oil, it was low, so I did it again.yep left side down! Pulled the air cleaner sponge off, it was saturated! Oil was pouring out the air hole. I pulled on the starter cord figuring I would pump oil out.Well I actually had to remove the pull cord assembly and use a pipe wrench - gently to get the engine to turn then I re-assembled the starter cord. Yep! Oil poured out like the Beverly Hills sitcom, but mine was clean. I have kept pulling until no more oil came out. Now what? I have replaced the gas line and primer blub,air filter and cleaned the spark plug. And will check the oil level WITH THE TILLER TILTED FORWARD. I'll replace the spark plug and try again. I'd be grateful for any suggestions. Thanks for the thread on the tine gear lubing and gear box - mine is working but you bet I'll keep it lubed! And I'll look for my manual - any suggestions as to where I can download one?

    Bookmark   March 14, 2010 at 4:26PM
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Apparently this is very common and never heard that it has lasting effect. You might want to take off the muffler and pour oil out if any!!!!

If now that you can pull the cord, make sure the oil level is correct, put gas and start the engine. Let it smoke for a few minutes. It will burn all the oil out and run smoothly in a minute or two.

    Bookmark   March 14, 2010 at 8:41PM
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I removed the broken priming bulb of my GX 31 roto tiller.
I am not sure that I installed the replacement correctly. There is a small spring that I do not remember where it came from and so I did not install it. I am not able to start the engine because gasoline is not flowing through the gas line. Please help.

    Bookmark   October 7, 2010 at 9:24PM
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I need HELP regarding replacing primer bulb of my honda rototiller gx 31, Please see my posting of Oct 7, 10. Thanks

    Bookmark   October 19, 2010 at 11:22AM
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Like scotty3259 I too filled the FG100 tiller with it on its side. I tried, but it would not start, so I poured oil out until it was the correct level. It starts now but once I give it gas it dies. It runs as long as I do not try to use it. Any suggestions would be great. Thanks!

    Bookmark   March 12, 2011 at 9:20PM
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Make sure the sponge air filter is not saturated with oil. Excess oil from the crankcase will pour out of the intake.

    Bookmark   March 12, 2011 at 9:26PM
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Same problem as Scott B. I have the air filter off, can get the rototiller to start and idle, but once I try to throttle it up, the engine dies.

    Bookmark   April 20, 2011 at 10:17PM
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