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Discussion Starter · #1 ·
Inspired by @bwdbrn1 and his GXV120 rebuild thread, I decided to undertake a project that will be a first time for me. A kick in the behind and some encouraging words got me going so I figured I'd document my little journey to the depths of a late '90's GXV 390. If I am successful, this will truly be a "if he can do it, anyone can" kind of undertaking. I've piddled a little prior to this but never really went all out on a rebuild/refresh. And honestly, neccessity is the reason why...having made a half dozen calls locally to see if there was anyone willing to do this for some of my $$$, not one shop/person was even remotely interested in tackling it. I just took that as a sign they were either too busy or they were independently wealthy & didn't need my $$$. So I am new here and I hope this is appropriate for me to do...I'm gonna learn a little about this and maybe someone else down the road will too. Mostly it will serve as a confidence-builder for first timers like myself.

Here's my little red mower earlier today.



Great little mower. Starts like a new one, mows perfectly, simple to operate and maintain...and it's red. :) Problem is she (yes, she's female) began puffing oil smoke and after checking all other possibilities, it is almost certain the rings are allowing oil past. She's much too pretty to send away and i just don't want to go buy a new thousand dollar throw away mower. I'm going to save this old girl from the junk yard if at all possible.

I'll continue to break this up as I progress. If anyone feels the need to jump in with sage advice or suggestion, you won't hurt my feelings at all. I am in no way declaring myself certified or professional in this area. I have mastered a few things...owned & operated a full-sized stinger-steered Peterbilt car carrier for over 40 years...married Wifey over 40 years ago and managed to keep her around...fathered & raised 2 of Kentucky's finest native daughters...things like that. But when it comes to getting inside an internal combustion engine...new guy right here.
 

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Discussion Starter · #2 ·
Here's a right side shot of her. You can see I'm a Honda fan boy...a little 25 horse outboard for my small pontoon boat hanging on a rack getting ready to install it.



Cleaned off some bench space for the upcoming project and got started.

Removed the deck. Gotta love the simplicity of these Honda Harmony riders.





About to get messy up in here.

 

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Discussion Starter · #3 ·
About an hour later, she was somewhat lighter in the front end. Again, extraction was a simple procedure which surprised me. I was expecting more labor than it actually required to get the engine loose & out.



Here's her heart on the bench ready for dismantle.

 

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Discussion Starter · #5 ·
Following @bwdbrn1 's lead on a GXV120, I felt my way around the 390, removing necessary items. Carb & air cleaner assy, linkage or controls for throttle, muffler & shields. Rotated via the flywheel until I could get the springs loose enough with a little thumb pressure, twisted the rocker arms and pulled the push rods. I used air impact like bwdbrn1 to remove the flywheel nut. Spun right off. However, if I were to pull the flywheel, I'm gonna need a different puller than the 2 I have. And the manual mentions a commercially available strap wrench to hold it. I don't have one long enough. If I'm gonna be doing much of this, I'll have to put that on my list. I can probably use one from Advance or Auto Zone as for the puller. Maybe a trip to Harbor Freight is in order? :)



Push rods look good as does most everything else so far. Until I loosen the 4 head bolts and give a little tug on the head. Slid the head off carefully, paying attention to the 2 dowels. Ugly in the combustion chamber. Carboned something awful. Here was evidence of where all my oil was going. I'm about to learn the best method for removing carbon deposits on the piston and valve area.

This is far as I got today. I'm seeing a ridge at the top of the cylinder and may be looking at visiting my old school machine shop bud or at the very least laying the hone to it to see if I can get it to a next sized piston. I have been told I can do it with a hone in my drill. Anyway, this piston was engraved with "ZF6W0" on the top. A little Googling revealed a new Honda piston engraved with "ZF6W01" for a 390 application. Images showed the rings positioned differently. I'll have to look into that if it is indeed for standard use and not a racing application. I'm not gonna be racing to anywhere but the dinner table.







Ugly innards !!!
 

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You're off to a great start! Props to you for undertaking it.

Nice 300ZX too!
 

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This is going to be fun! I always like looking beyond the actual project and sneaking a peek at other folk's garages. I can see you're all set. First and foremost, you have the proper attitude, beyond that, let's see:

1. Cleared work space...check
2. Official Honda shop manual...check
3. Ceegar...check
4. Big rubber mallet...check
5. All the tools you'll need...well, most of them for now anyway...check
(Doing this sort of stuff is always a great excuse for adding to the tool box)
6. Camera for documentation (and memory lapses)...check

What else...Note book and a nicely sharpened #2 pencil for keeping notes or making notations in the shop manual.

When removing something that requires taking multiple bolts out, like the oil pan, where the bolts might be of differing lengths, refer to the manual for the recommended procedure. If the manual doesn't say which one to start with, choose one next to say the starter, go around in a clock wise direction, and lay them out where they won't get disturbed in the order they came out from left to right. This way, when you go to put it back together, you know where to start and where the bolts go.
 

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Great job so far!! That tractor is very worthy of saving!!! Glad you found Bruce an inspiring! He is great guy!
 

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Discussion Starter · #10 ·
You're off to a great start! Props to you for undertaking it.

Nice 300ZX too!
Thanks, Austen ! I like to piddle. :ThumbUp:

Thanks for the flowers on the Z car also. It's an '85 manual with 49,000 original verified unmolested one owner miles on it. Still has the old R12 in the A/C and it blows cold as December. Always garaged and sold here in town when new. Possibility I even hauled it from the port in Jacksonville back then. I was working out of Jax port hauling new Datsuns/Nissans when this was shipped to the dealer. No way of knowing for sure if I was the one but a good chance because those dealers in this area was my home loads for the weekends and I hit that dealer every chance I got. :) Bought it and parked it in garage...start it and drive it every few months just a little to keep things limbered up. Kinda dusty at the moment. Lot like myself...old and stiff and dusty.

 

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Discussion Starter · #11 ·
This is going to be fun! I always like looking beyond the actual project and sneaking a peek at other folk's garages. I can see you're all set. First and foremost, you have the proper attitude, beyond that, let's see:

1. Cleared work space...check
2. Official Honda shop manual...check
3. Ceegar...check
4. Big rubber mallet...check
5. All the tools you'll need...well, most of them for now anyway...check
(Doing this sort of stuff is always a great excuse for adding to the tool box)
6. Camera for documentation (and memory lapses)...check

What else...Note book and a nicely sharpened #2 pencil for keeping notes or making notations in the shop manual.

When removing something that requires taking multiple bolts out, like the oil pan, where the bolts might be of differing lengths, refer to the manual for the recommended procedure. If the manual doesn't say which one to start with, choose one next to say the starter, go around in a clock wise direction, and lay them out where they won't get disturbed in the order they came out from left to right. This way, when you go to put it back together, you know where to start and where the bolts go.
I got all the above...even the pencil and the notepad.

Thank you, Bruce...sounds better than calling you bwdbrn1...I can't figure out what that is abbreviation for.

All the oil pan bolts on this 390 (389) were the same length except one. I marked it after reading your advice in that other thread. Just taking my time but it goes along fairly quick. Only issue I had this evening was one of the four bolts that mount the engine to a pair of "legs that in turn mount to the chassis. 3 came easy...one was corroded or crossed and was coming a little hard. My mistake...put an impact on it and tried to go slow but twisted it off. Not a big deal though. I'll grind it flat and drill it out. It's not one of the oil pan bolts...just a mounting bolt. Lesson learned. Surprised how easy everything is going actually. I was thinking with the age maybe someone had been into this before but it's all original apparently as far as I can tell.

I may have found my problem after sliding the piston out of the combustion chamber slowly. The ring gaps were lined up! At this point I must ask...will the rings actually move/rotate after a period of time/age? I'm certain Honda would never have assembled it this way and it didn't smoke until this year.



And if they are not supposed to rotate in their slot, what should I be looking for? I have a dial caliper but didn't use it yet but I did take a feeler gauge and try to get an idea of piston to cylinder clearance. It was pretty tight and still within the manual's specs as far as the feeler gauge goes. It took a good deal of pushing to get the piston out and there were no broken rings. I know there's better ways to determine but several vids from various small engine guys say one can use feeler gauges with decent success most of the time. I was careful not to scratch or gouge.

The cylinder is void of any hash markings at all...slick as a baby's bottom. No scratches or defects except the ridging at the top there in the pics. While I'm far from being qualified to make this statement...the entire engine looks very clean inside and all is tight. No play anywhere I can find at all in camshaft or balancers. Bearings all appear to be like new. Honda Robert gave me some info on this particular unit and it's around a 97 or 98 model IIRC. I thought I'd be seeing a worn out engine inside but it looks very good all except that carboned, oily piston top and valves from the oil that was going thru it and that ridge which could be a part of the smoking problem.



I've done a little cleaning on the head. I'd like to get further into it and make sure the valves and the seats are clean. Just trying to take care and not scuff nothing.

I've got a 220 medium grit honing tool I'm going to use on the cylinder. And I looked for numbers on the piston but all it has is the ZF6W0 stamped on top and a ZF6 on the side. I am assuming it's original. I'd like to just ring it and hone the cylinder and put it back together after cleaning the head and get back to mowing.
 

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Thanks, Austen ! I like to piddle. :ThumbUp:

Thanks for the flowers on the Z car also. It's an '85 manual with 49,000 original verified unmolested one owner miles on it. Still has the old R12 in the A/C and it blows cold as December. Always garaged and sold here in town when new. Possibility I even hauled it from the port in Jacksonville back then. I was working out of Jax port hauling new Datsuns/Nissans when this was shipped to the dealer. No way of knowing for sure if I was the one but a good chance because those dealers in this area was my home loads for the weekends and I hit that dealer every chance I got. :) Bought it and parked it in garage...start it and drive it every few months just a little to keep things limbered up. Kinda dusty at the moment. Lot like myself...old and stiff and dusty.
Good stuff!! That's pretty cool that you have that fallowing with it.

Wow, that's unbelievably low mileage! Don't ever sell it.

Datsun/Nissan Z cars are great cars, aren't they. I had a 280Z that I fixed up several years ago... fun car. :2th:
 

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Discussion Starter · #13 ·
Great job so far!! That tractor is very worthy of saving!!! Glad you found Bruce an inspiring! He is great guy!
Thanks Eric. And thanks for putting a name to the handle. I agree...he seems to be a very helpful kinda gent. And I needs all the help I can get. :)
 

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Discussion Starter · #14 ·
This is shaping up to be a nice rebuild! Keep us posted! :ThumbUp:
Thanks MotorHead from NY. :ThumbUp:

If I can hit the key switch and it fires like Bruce's 120 build...I'll be a happy grass cutter. But I still hate dumping them cans on the back !
 

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Lot like myself...old and stiff and dusty.
Me too....but we're just as capable as ever!

I've not run across rings that were lined up like that. You may be right about that being the cause of the problems with your engine.

I'm really enjoying your thread and following your progress.
 

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Discussion Starter · #17 · (Edited)
Ooops ! I screwed up. Re-organized my Photobucket and it changed the links to all my images. I'll fix 'em back before I continue on.

:sorry:

OK...got all but one image straightened out but too much time has passed for me to edit the link. I'll try not to do that agin.
 

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Discussion Starter · #18 ·
Onward...slowly.

A little more accomplished today. I had not yet ordered parts because I wanted to get a look see at the piston and cylinder clearances best I could with the tools I had available to me. Didn't know if I was gonna be in the oversize range. Apparently not by my crude measurements and standard specs in the manual.

So today I first removed the top ring from it's groove in the piston and placed it just inside the cylinder. I wanted to get an idea where I was at with the ring end gap. So I inverted the piston and left the second ring in it's groove and inserted it to "square" up the first ring. Pushed the piston to the second ring and removed the piston. Looked fairly square to me. I used a dial caliper and feeler gauges to get my measurements today...didn't have a more expensive tool i.e. a Starrett, etc. I think this will suffice here in my case.





In addition to the ring gaps being lined up when I first removed the piston, I have now discovered another contributor to the oil smoke and usage. The manual says ring end gap should fall in the 0.008 to 0.016 territory. Recommendations in the Honda manual place the service limit on this end gap measurement at 0.040. I am at 0.0625 using feeler gauges and that ring slid in beyond that nastiness at the top of the bore. (I'll get that cleaned up shortly).

Now I measured the cylinder ID and the piston skirt OD and I'm nowhere near requiring an up-sized piston. It's still well within the service limits noted in the manual. Soooo...just rings? And install them staggered? I'm thinking this will fix my little red rider right up! Celebration time? Maybe not just yet but I'm always ready for food...

 

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Discussion Starter · #19 ·
Now it's time I see what I might need in the cylinder head department cause I need to get the parts ordered. Cleaned off another table top lest Mr. Bruce chastise me with leather strop or keyboard strokes.



Used my fat thumbs to place enough pressure downward on the springs to get the caps & springs loose from the valves. Didn't have a suitable valve spring compressor unless my thumbs qualify. Today they did. A note on this engine...on the bottom valve in the image below...believe it's the exhaust valve...sitting at the puter tonight I can't remember for sure...there's a small cap on the valve that Honda calls a valve rotator and the manual makes mention of it's importance for forgetful folks. You can see the diff between the 2...the top of the exhaust valve has got the "button" or valve rotator...the intake does not. I won't forget it when I go back together. That would not be the part of this I like...having to go back. I hate going back over something I already did...unless it's the grass and I'm striping it for Wifey. When I was truckin' I'd take alternate routes to get back home to keep from re-tracing the miles I just traversed the day before.

 

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Discussion Starter · #20 ·
I removed the valves and checked for any play at all in the guides. I did my best to measure the valve stems by the manual and they are straight and not worn...no play. The valve guides have remained "centered"...by that I mean they have not wallowed their holes in their 18 years of lawn mowing duties. I'm going to leave the valve guides/seats alone except for doing the lapping deal with compound & suction cup dowel. The exhaust side here is badly carboned and it's a mystery to me how it ran as good as it did. I'm soaking the valves, the piston and the ports of the head itself in a couple inches of Berryman's Chem-Dip. I worked trying to get the combustion area clean of the carbon but that's tough stuff and the Chem-Dip is the only thing I have found that will really make short work of the blackness. I also just added a new exhaust and intake valve to my order just because I wanted to. Probably could've cleaned these up tomorrow but I don't want to chance it.

 
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