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Honda GXV120 rebuild

#1

C

Chris Parman

Hello Everyone, I tore down my GXV120 and I took some pictures of initial important parts and surfaces. At a first look at surfaces, from a wear perspective how do the pictured look? I just need some advice on replacing or reusing?. Secondly, from a piston perspective replacing piston and rings (keeping standard specs) and just hone? Or a complete bore and hone? Thank you in advance for you help.

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#2

M

mechanic mark


I would purchase a shop manual for your engine, it will give you all the information you will need, wear limits, what to look for when inspecting after disassembly, step by step instructions, etc.


#3

T

tadawson

Reuse any and everything that is within service specs . . . might just need rings and a light deglaze/hone, but wom't know until you measure it. Considering age, I would def. replace all seals though . . . My GXV140 were so dry, aged, and shrunken they they pretty much fell out . . . and the 140 is even older . . . Seals are cheap, and you are there!


#4

C

Chris Parman

tadawson said:
Reuse any and everything that is within service specs . . . might just need rings and a light deglaze/hone, but wom't know until you measure it. Considering age, I would def. replace all seals though . . . My GXV140 were so dry, aged, and shrunken they they pretty much fell out . . . and the 140 is even older . . . Seals are cheap, and you are there!
Click to expand...

Tadawson, thank you for the reply. By the way, before I tore the engine down it was blowing white smoke however the white smoke dissipated after it the engine warmed up. When it ware warmed up is was blowing less white smoke (if that makes sense). Let me know your thoughts.


#5

tom3

tom3

I'd ring it and run it. New seals and gaskets. What kind of oil are you running in it?


#6

C

Chris Parman

tom3 said:
I'd ring it and run it. New seals and gaskets. What kind of oil are you running in it?
Click to expand...

tom3: When I bought the HR214 (a month ago) I changed the oil and used 10W-30 (Conventional oil). Even after the oil change it still blow white smoke and today I tore it down.


#7

tom3

tom3

One thing you have to watch on these air cooled motors is the oil rating. A lot of the 10w30 oils are not correct for that type of use. Might explain some of the wear showing on the aluminum parts. If you have a user's manual look for the API rating required. Probably not the SM or SN as most of today's automotive oil is rated. Actual Honda, or maybe Kohler 10w30 oils might be best for that.


#8

J

jp1961

Hello,

From your pics, the internals don't look too bad. These dimensions are listed in my Intertek manual for the GXV120, standard cylinder bore diameter is 2.262" - 2.363" cylinder bore diameter. Standard piston diameter measured at the lower edge of the skirt and 90 degrees from piston pin bore is 2.360" - 2.361". Valve stem to guide clearance is .001" to .002". Standard valve guide inside diameter is .2165" - .2170". Standard valve spring height is 1.339". Standard rod journal inspection for automotive use was to rub a penny (an old copper one not the new copper plated steel ones,,,lol) on the journal, if any copper is deposited, journal needs polishing. Let me know if you need another dimension not listed. I would lightly hone and install new rings.

Regards

Jeff


#9

T

tadawson

Chris Parman said:
Tadawson, thank you for the reply. By the way, before I tore the engine down it was blowing white smoke however the white smoke dissipated after it the engine warmed up. When it ware warmed up is was blowing less white smoke (if that makes sense). Let me know your thoughts.
Click to expand...
That's what my 140 was doing . . . . deglaze/ring/seals, and run it (unless you find something else). The sleeve in these Hondas seem to hold up quite well.


#10

I

ILENGINE

Cylinder still shows a hint of cross hatching so very little wear there, but there is evidence of hot spotting so need to deglaze and new rings.


#11

tom3

tom3

Question, maybe kind of dumb. When you took apart the motor was there a lot of cut dried grass and dirt in the cooling fins? Might explain some of the wear and resulting oil use.


#12

C

Chris Parman

tom3 said:
Question, maybe kind of dumb. When you took apart the motor was there a lot of cut dried grass and dirt in the cooling fins? Might explain some of the wear and resulting oil use.
Click to expand...

Tom, no the cooling fins were clear of debris.


#13

C

Chris Parman

Here some pictures of the Cylinder head and Valves. I clean the cylinder head in a Ultrasonic cleaner and it came out pretty clean except for the exhaust runner and valve pocket, which I already started to grind out the carbon build up. I'm not entirely sure if this engine ever had valve steam seals and I did see evidence of any seal debris in the oil sump. Also, there is quite a lot of carbon build up on the exhaust valve (see pictures) not sure if its due to worn piston rings or valve guide. However, initially when I took off the cylinder head I noticed a small pool of oil at the bottom of the cylinder when the piston was at top dead center. I know I need to oder the GXV120 Service manual (and I ordered the manual today from Honda), I was just wanted your thoughts thus far in the rebuild cycle. As always I appreciate everyones input.

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#14

J

jp1961

Hi Chris,

The exhaust valve on my GXV140 looked similar. I used a Dremel hand grinder with wire wheel to remove most of the carbon and did resurface the valve seat face with the compound on my lathe set to 45 degrees. If you had a pool of oil in the cylinder, I would suspect it's leaking past the valves. Is there a lot of play in the valve stems when inserted into the head?

Regards

Jeff


#15

C

Chris Parman

There is slight play for both the Intake and Exhaust valve to valve stem guide, more so with respect to the Exhaust valve. I can feel it at the spring end, as opposed to the combustion chamber end of the valve. If it's the valve stem guide it's going to be tough because I don't have special tools.


#16

J

jp1961

Hi Chris,

Assuming you have a 0-1.00" micrometer, i'd try to find the largest diameter rod that will fit into the valve guides and then mic your valve stems where they come into contact with the valve guides, if > .001" I'd replace the valve guides. Mine were within 1/2 thou or so (i.e. .0005"). I understand about not having special tools, my Intertec manual says a special tool is needed to install the guide(although a right sized deep well socket would probably work) and they must be reamed after installation, again using a special reamer, however reamers can be purchased at like .0005 increments.

Correction on the cylinder bore diameter,,,the Intertec manual says 2.262-2.363, I believe is a typo (by Intertec, not me) I think they mean 2.362"-2.363. Makes sense as the piston is 2.360"-2.361". Sorry,,,I try to triple check what I type for accuracy.

Jeff


#17

logert gogert

logert gogert

hey guys, i know this is off topic, buuut lets say i wanted to rebuild a engine, ( which i don't )
HOW do you get those precise measurements, i mean you can't just whip out a ruler and go, alright the cylinder is 3.0001276
like wut?


#18

J

jp1961

Hello,

You need a 0-1.00" micrometer and 0-6" set of calipers. a set of bore micrometers is useful too.

Regards

Jeff


#19

J

jp1961

jp1961 said:
Hello,

You need a 0-1.00" micrometer and 0-6" set of calipers. a set of bore micrometers is useful too. A machinist rule usually goes down to 1/64" increments, which is REALLY hard to read unless you're eyesight is very good. For this old fart i use the 1/32" scale.

Regards

Jeff
Click to expand...


#20

logert gogert

logert gogert

?
whats post #19 supposed to mean
you already said it in post 18 so, was it an accident


#21

Hammermechanicman

Hammermechanicman

If you have a outside micrometer measure the valve shaft diameter up near the keeper area then measure along the valve stem in the area where the stem rides in the guide. If there is any difference i would replace the valves and lap them in. Unless you are planning to race the engine or the like i would not worry about the guides.
Hone the cylinder, new piston and rings, new valves lapped in, seals and gaskets and i bet you will be good to go. As Taryl would say. It's not the space shuttle. ?


#22

C

Chris Parman

jp1961 said:
Hi Chris,

Assuming you have a 0-1.00" micrometer, i'd try to find the largest diameter rod that will fit into the valve guides and then mic your valve stems where they come into contact with the valve guides, if > .001" I'd replace the valve guides. Mine were within 1/2 thou or so (i.e. .0005"). I understand about not having special tools, my Intertec manual says a special tool is needed to install the guide(although a right sized deep well socket would probably work) and they must be reamed after installation, again using a special reamer, however reamers can be purchased at like .0005 increments.

Correction on the cylinder bore diameter,,,the Intertec manual says 2.262-2.363, I believe is a typo (by Intertec, not me) I think they mean 2.362"-2.363. Makes sense as the piston is 2.360"-2.361". Sorry,,,I try to triple check what I type for accuracy.

Jeff
Click to expand...

Hello Jeff, I found this online

GXV120_1.PNG

But I don't understand the clearance meaning of 0.20 +/- 0.02mm (0.008 +/- 0.001 in)


#23

J

jp1961

Hi Chris,

Hmmm,,,hard to interpret this chart. I'm guessing for your GXV120 engine the intake should have .15 MM clearance for the intake and .20 MM clearance for the exhaust. Not quite sure if this is the clearance for the valve stem to guide clearance or the amount the valve opens?

If the values in brackets are imperial measurements or inch base,,,,.006" seems very loose for the valve stem clearance, somewhat like a baseball bat in a rain barrel.

Jeff


#24

J

jp1961

Hi Chris,

I'm guessing you want as tight a clearance in the valve stem to valve guide clearance, Too tight and the valve stem will bind, too loose and oil will escape into the combustion chamber. Your talking tenths here,,,(i.e. .0001")

Keep in mind as metal gets hot, it will expand, as long as the guide is made from similar material, it will expand at the same rate.

Regards

Jeff


#25

logert gogert

logert gogert

Hammermechanicman said:
If you have a outside micrometer measure the valve shaft diameter up near the keeper area then measure along the valve stem in the area where the stem rides in the guide. If there is any difference i would replace the valves and lap them in. Unless you are planning to race the engine or the like i would not worry about the guides.
Hone the cylinder, new piston and rings, new valves lapped in, seals and gaskets and i bet you will be good to go. As Taryl would say. It's not the space shuttle. ?
Click to expand...
oh cool, you know who taryl is?
like, taryl fixes all?
if thats who your talking about, i could honestly care about his mowers, i just wanna see how fast he can eat an ear of corn. LOL not really
sorry I'm so mean lol


#26

I

ILENGINE

Chris Parman said:
Here some pictures of the Cylinder head and Valves. I clean the cylinder head in a Ultrasonic cleaner and it came out pretty clean except for the exhaust runner and valve pocket, which I already started to grind out the carbon build up. I'm not entirely sure if this engine ever had valve steam seals and I did see evidence of any seal debris in the oil sump. Also, there is quite a lot of carbon build up on the exhaust valve (see pictures) not sure if its due to worn piston rings or valve guide. However, initially when I took off the cylinder head I noticed a small pool of oil at the bottom of the cylinder when the piston was at top dead center. I know I need to oder the GXV120 Service manual (and I ordered the manual today from Honda), I was just wanted your thoughts thus far in the rebuild cycle. As always I appreciate everyones input.

View attachment 50823 View attachment 50824 View attachment 50825 View attachment 50826 View attachment 50827 View attachment 50828 View attachment 50829 View attachment 50830
Click to expand...

I looks like the exhaust valve wasn't sealing properly which can cause oil usage. Also oil in the bottom of the cylinder could be cylinder wear, but could also be just oil seepage past the ring while setting.
logert gogert said:
hey guys, i know this is off topic, buuut lets say i wanted to rebuild a engine, ( which i don't )
HOW do you get those precise measurements, i mean you can't just whip out a ruler and go, alright the cylinder is 3.0001276
like wut?
Click to expand...

You need to have a bore gauge and micrometers to measure the bore gauge down to the nearest thousands. I have a dial type bore gauge that measures .0005 but you still need the micrometers to set the standard bore size to calibrate the bore gauge to find out of round and oversize.


#27

I

ILENGINE

Chris Parman said:
Hello Jeff, I found this online

View attachment 50836

But I don't understand the clearance meaning of 0.20 +/- 0.02mm (0.008 +/- 0.001 in)
Click to expand...
Those are rocker to valve stem clearances. And the .20+/-.02(.008 +/-.001) means the valve clearance for the exhaust valve is .18-.22 mm or .007-.009 inch.


#28

T

tranchinh

I'd re-ring and hone the cylinder a little ,lapping the valve then it run good ,never see cylinder that worn out to out of spec on these engine ,Piston sometime need to replace .


#29

S

steve581581

Where do you guys buy your parts from? I've got the same engine that I'm rebuilding and my local shop can't get new valve guides or seals and I'm waiting to hear back from them about the gaskets and rings.


#30

C

Chris Parman

steve581581 said:
Where do you guys buy your parts from? I've got the same engine that I'm rebuilding and my local shop can't get new valve guides or seals and I'm waiting to hear back from them about the gaskets and rings.
Click to expand...
Hello Steve: It really depends on the lawn mower model and/or the VIN number on the engine itself. For example the GXV120 I rebuilt some 3 years ago was attached to a HR214SX. From what I found on (boats dot net), only the exhaust valve guide is available. Valve seals were never a original part per the GXV120 engine head. Here is the URL -> https://www.boats.net/catalog/honda/lawn-mowers/hr214-sxa-2-vin-hr214-6235981/cylinder-head


#31

S

steve581581

Chris Parman said:
Hello Steve: It really depends on the lawn mower model and/or the VIN number on the engine itself. For example the GXV120 I rebuilt some 3 years ago was attached to a HR214SX. From what I found on (boats dot net), only the exhaust valve guide is available. Valve seals were never a original part per the GXV120 engine head. Here is the URL -> https://www.boats.net/catalog/honda/lawn-mowers/hr214-sxa-2-vin-hr214-6235981/cylinder-head
Click to expand...
Thank you. I used to have 2 of them but gave the other away years ago like a dummy when the lower crank seal started leaking.


#32

C

Chris Parman

steve581581 said:
Thank you. I used to have 2 of them but gave the other away years ago like a dummy when the lower crank seal started leaking.
Click to expand...
You had have two of what? Anyway, if you need to replace the exhaust valve guide they are available. However, in my experience with old GXV120's, the intake valve to intake guide clearance is usually in service specifications and doesn't need replacing. Now the exhaust valve to exhaust guide clearance is usually out of service specification and the valve guide will need to be replaced.


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