[jcross312]

Hone


Hone the cylinder, clean up the piston, install new rings, clean up the valves (lap them), new head gasket if it needs it, and run it.

That's a good plan. Gonna need a connecting rod too tho, no? This one still measures good, but it's galled up.

I'm very tempted to get the one with the oil slinger (gx) and trim it off, much cheaper than the gxv one without it. I think thats the only difference. Price difference is due to the volume of parts made for the gx vs the gxv would be my guess

 

[jcross312]

Custom bore gauge 😆

Bamboo skewer cut to the right length

Looks like I'm within specs on the cylinder

 

[jcross312]

Honed the cylinder. Looks mostly round and uniform still, no bad spots. This was a new 4" stone hone, (rented from oriellys) "medium" grit is all it says. Might have done with fewer passes, but still measures good, according to the stick.

I'll clean it up good with some soapy water and a scotch Brite pad eventually

 

[Scott87]

Whats with the janky spot?

 

[jcross312]

Whats with the janky spot?

Talkin about the black spot? Thats grease or something. Should have wiped it better before taking a pic

 

[jcross312]

Found a place with pretty good deals on oem honda parts. Can get connecting rod, piston, rings, pin, clips,seals, and a pan gasket for under $200.

I think I'm gonna reuse the head gasket. It's metal and looks fine (and a new one is over $50)

The piston I decided to go with Stens and save about $30. They look to be high quality

And the rod, is for a GX, not GXV. Price difference is $75. I spent quite a while looking at both, and only difference I see is the GX has the oil slinger. My plan is to trim it off with a cutting disc and roll with it and stick the $75 in my pocket

 

[jcross312]

I checked the condition of the valves/seals by pouring gas into the ports. Both held gas and didn't leak

 

[jcross312]

One more update until the parts arrive. Doing crank seals, gov shaft seal ($4 and it is low on the block-potential future leak), dipstick o-ring, new valve stem seals ($6 each, why not) gonna lap the valves, replace the loose fitting breather hose ($7) new rocker cover gasket (old one broke, was hard), air filter, plus all the stuff mentioned on my last post

Was gonna replace the o-ring that goes between the pan and the block that seals the oil galley that sends the pressurized oil to the topend, but was a long delay on it. Maybe can find one local close enough to work. I think a hydraulics shop nearby may have one that would work

It's a small, cheap part, but an important part. The old one looks ok, but it's old and should probably be changed while I'm there

The stuff I ordered will take a week or so to arrive

All the parts came out right at $200+/- a few dollars, so not bad. The time spent fooling with this thing is racking up tho. Right now I have some extra time to spare, so it worked out

Here's a pic of the o-ring I was talking about. It looks like it's probably fine anyway. The mating surface on the pan looks good too

I might be slightly wrong about what the o-ring is for, looks like it seals an oil jet that sprays oil on the connecting rod/crank as it rotates. (You can see the jet close to the crank bearing)

Maybe it also sends oil up to the head, but being a vertical shaft, looks like oil may just slosh up there...?

 

[CTinline-six]

Yup, honed the cylinder on the one I did, lapped the valves and new gaskets. I replaced every seal or o-ring I could find, because like yours the engine I did was hemorrhaging oil.

 

[jcross312]

Looks like I'm good to go with the GX conn rod. Looks identical except for the slinger. They charge an extra $80 for the non-slinger model. (Everybody knows pricks are a dime a dozen 😄)
Gonna trim it and should be good. (Please correct me if im wrong)

Got another piston on the way

 

[Smithonite]

As long as the clearances are good and the length doesn't push the piston into the valves, should be good. Looks good from here!

 

[jcross312]

As long as the clearances are good and the length doesn't push the piston into the valves, should be good. Looks good from here!

I test fit it to the crank and the big end fits perfect. Measured the length with a caliper and it's the same from big end to small end. 👍👍

Also tested the wrist pin, small end. Again, perfect fit. The GX rod was like $20 and some change, the gxv was acultually around $118 from the place I got the parts from. Found one or 2 on ebay around $100, but we ain't talking about that right now 😄.

This might be Hondas best kept secret. Making millions off gxv390 owners around the world

 

[Smithonite]

Ain't the first time I've seen that. I remember GM 900-series 1500 pickups from '07-'12 having EVAP issues due to canister vent clogging. You could buy the truck one for deep into $100 territory ... OR, buy one for a Cadillac, which ironically and amazingly was cheaper and the EXACT SAME PART - just had a different part number.

 

[CTinline-six]

I test fit it to the crank and the big end fits perfect. Measured the length with a caliper and it's the same from big end to small end. 👍👍

Also tested the wrist pin, small end. Again, perfect fit. The GX rod was like $20 and some change, the gxv was acultually around $118 from the place I got the parts from. Found one or 2 on ebay around $100, but we ain't talking about that right now 😄.

This might be Hondas best kept secret. Making millions off gxv390 owners around the world

I'm sure some of it is the GX being a much more common engine. Before I rebuilt the GXV390 on my friend's mower we tried looking locally for a used engine, and there was only one within 100 miles. Plenty of GX engines though.

 

[jcross312]

I'm sure some of it is the GX being a much more common engine. Before I rebuilt the GXV390 on my friend's mower we tried looking locally for a used engine, and there was only one within 100 miles. Plenty of GX engines though.

I looked for a used one also. Only thing I found was a new, never used GXV390 on marketplace for $350! Only problem was it is 5 hours away

Yes, the volume of parts for the gx is why they are so much cheaper, I'm sure

 

[jcross312]

Man, that was alot of work for a nickel.

After ordering another piston from local Honda dealer, using the same parts schematic I used to order the rings, verifying serial # breaks, I gave them the part number I needed.

The guy on the phone said, ok, the number changed, and got it ordered. I thought it was strange he said the number changed, since I had already checked online and it didn't show a number change. Whatever

Got it in and had it on the conn rod, ready to install in the cylinder, and then tried to put the new honda rings on it. Rings were too thick

I knew right then, the old piston was going back in it. Done ordered 2 pistons and couldn't use either one.

I spent about 3 seconds measuring the skirt for wear and didn't even seem .001 worn. Eff it, put it in.

All in all, got way to much time and energy in this thing, but it did crank on the 1st pull and runs good so far. Got 5 minutes on it 😁

I think Breez suggested just replacing the motor on the 1st reply. Probably not a bad idea in hindsight. It was alot of time and hassle for a rebuilt engine. Hope it last awhile. It is running and sounding good tho

 

[Smithonite]

Sounds like there's definitely some confusion with the part numbers. That usually doesn't happen with Hondas. Any chance that was a chinese clone, or had chinese clone parts installed on it prior? That's a huge problem today - they can copy literally ANY part of a Japanese engine. That's when the trouble starts.


Years ago I rebuilt a Kawasaki engine for a buddy of mine after he snapped of a bolt so badly in the crankshaft that I had to swap cranks. No way that broken bolt was coming out! Was way down inside. Drilled, heated to a million degrees, tried Easy Outs - nothing worked. Was easier to just grab a crank off eBay and do the swap.

That saved him a PILE of money and he's still using it today, 5 years later. Definitely the way to go if you have the patience and ability.

 

[jcross312]

Sounds like there's definitely some confusion with the part numbers. That usually doesn't happen with Hondas. Any chance that was a chinese clone, or had chinese clone parts installed on it prior? That's a huge problem today - they can copy literally ANY part of a Japanese engine. That's when the trouble starts.


Years ago I rebuilt a Kawasaki engine for a buddy of mine after he snapped of a bolt so badly in the crankshaft that I had to swap cranks. No way that broken bolt was coming out! Was way down inside. Drilled, heated to a million degrees, tried Easy Outs - nothing worked. Was easier to just grab a crank off eBay and do the swap.

That saved him a PILE of money and he's still using it today, 5 years later. Definitely the way to go if you have the patience and ability.

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No, it's for sure a Honda. I don't think they ever copied the GXV (vert. shaft)

The 1st piston was the right one, but had a casting flaw, the second, I'm pretty sure I came up with the right part number, but when I called it in to the local Honda dealer, he said the p/n changed. He gave me such a good deal, I kinda don't even want to return it. Maybe just give it back to them tho. The ring groove was way too narrow for the rings to fit...

 

[CTinline-six]

No, it's for sure a Honda. I don't think they ever copied the GXV (vert. shaft)

The 1st piston was the right one, but had a casting flaw, the second, I'm pretty sure I came up with the right part number, but when I called it in to the local Honda dealer, he said the p/n changed. He gave me such a good deal, I kinda don't even want to return it. Maybe just give it back to them tho. The ring groove was way too narrow for the rings to fit...

Yeah what I've learned from working on small engines is that the spec numbers are very important and often there are several of them for one engine model. I'm sure it's for different upgrades and changed parts over the years. To my knowledge the larger GXVs have not been copied, but the smaller GXV160 on lawnmowers has been copied.

 

[Smithonite]

Yeah, they put those things in 100 different applications, so they have to have different intake, filter designs, and exhaust routing to fit the different units, hence the spec #.