Honda GX-390 Rebuild (Pict. Heavy)

[shakey0818]

I was bored and decided to see what condition my GX-390 power washer engine was in.It is about 10 years old and has been sitting outside uncovered the whole time.I looked in the gas tank and it had a lot of surface rust.I then realized it was going to take more than gas and cleaning the carb to get going.
Not having any engine experience other than cleaning a few carbs and getting an old snow blower running I decide to give it a go.
I take the tank off and spray some PB Blaster in it.I then take almost everything off inspect.When taking everything off i put back in all the bolts and take many pictures so i can remember how it goes back.I'm good at taking things apart but putting them back together is another story.I noticed that the carb and cylinder is full of rust build up.It seems like an easy cleaning and i might be able to get this thing running again.
I'm not sure of a few things and have a few questions.This will prob take some time i'm in no rush and don't know what the engine is going into yet.
1)Can the rust in the cylinder just be sanded down gently?
2)Should i get some type of gasket rebuild kit?(all gaskets look nice).
3)I have no clue what that little black plastic piece is.It came from inside the engine.I thought it was part of the low oil thing inside the engine but it wasnt.
4)do you thing a simple cleaning will do or should i buy a whole engine re build kit?

The engine was running like a top before and seemed to have compression when i took it apart.

Thanks for the help guys.

Rob

 

[shakey0818]

 

[shakey0818]

Here's a few more.

 

[OzFab]

It is about 10 years old and has been sitting outside uncovered the whole time.

That's what happened to the engine on my riding mower; when leaving an engine to sit, it should be aligned on the compression stroke so no moisture can enter & destroy the bore

Not having any engine experience other than cleaning a few carbs and getting an old snow blower running I decide to give it a go.

Everyone has no experience the first time, you have absolutely nothing to lose (except maybe a few dollars )

When taking everything off i put back in all the bolts and take many pictures so i can remember how it goes back.

That's a good habit to get into Just remember, some of the bolts may need to be removed to work on the engine; either wrap them in paper tape (masking tape) & mark them or bag & mark them

I'm good at taking things apart but putting them back together is another story.

I think we've all been there

I noticed that the carb and cylinder is full of rust build up.It seems like an easy cleaning and i might be able to get this thing running again.

I saw that coming...

1)Can the rust in the cylinder just be sanded down gently?

If it is only surface rust, you may get away with it but, I have a feeling there's gonna be some pitting there, which means you're up for a rebore; the smallest imperfection in the bore (cylinder wall) will damage the rings & possible do more damage to the bore...

2)Should i get some type of gasket rebuild kit?(all gaskets look nice).

Again, sometimes you can get away with it but, at least replace the head gasket

3)I have no clue what that little black plastic piece is.It came from inside the engine.I thought it was part of the low oil thing inside the engine but it wasnt.

That's a mystery; I'm sure you;ll figure it out as time goes by...

4)do you thing a simple cleaning will do or should i buy a whole engine re build kit?

Honestly, no, a simple clean won't last long, get a full rebuild kit including oversize piston & rings

 

[shakey0818]

Thanks for the reply Fabroman.I think your right about the rebuild kit and the rebore.Like i said i'm in no rush right now and my funds are going towards my mini bike build.
Do you think its worth getting a bigger cam and trying to make it hi-performance?

 

[OzFab]

It can't hurt but, it depends on the application (as in, what will the engine be used for). If it's omly going back on a water pump, it's a bit of overkill...

Also, it looks like you got lucky with the PTO, it's straight cut! Most water pumps have a tapered PTO shaft

 

[shakey0818]

It can't hurt but, it depends on the application (as in, what will the engine be used for). If it's omly going back on a water pump, it's a bit of overkill...

Also, it looks like you got lucky with the PTO, it's straight cut! Most water pumps have a tapered PTO shaft

I would like to find a go cart or mini bike for it.I live next to a beach so maybe something to ride on the beach with suspension.
Yeah the pump went on it after i let a friend use it.I prob could re build it for less than $100 but i just got a new one 3 years ago.For $1000 i could replace the whole power washer every year.I make some good money with it.

 

[landuse]

You could maybe try and give the bore a hone and see what it looks like. Just remember that you cannot just take sandpaper and go crazy in the bore. It needs to be sanded (or honed) in a certain way. Like Fabroman says, if it is surface rust you should be OK. That carb of yours looks a little too rusted, and I am not too sure if you can save it, but you can only clean it and see what it does after.

 

[fowler]

best bet

get a blown engine and use the bits

if it were mine and all i wanted to do was make it run then id just get some emry tape and crc on the bore
it would run rough but it would run

i dont like the chances of that bore being useable
thats alot more that surface rust

where do u live?
got a few old gx390s sitting here just collecting dust

but if u could get a flapper disc in there to take the rust off then go from there

 

[OzFab]

That carb of yours looks a little too rusted, and I am not too sure if you can save it, but you can only clean it and see what it does after.

Hold up, that has to be superficial; think about it, a carb is mostly alloy & brass, WHICH DON'T RUST! Boil that sucker in lemon juice & it should come up fine...

 

[shakey0818]

I'm in Rhode Island.I think the carb will be an easy clean.I like the idea of the flapper disk then polishing it .I think it may be too far gone.I think Fabroman had it right by saying to have it bored over.My cousin is engine builder.I'll have him take a look at it and tell me if it's worth saving.If it's not then i will be looking on craigslist.

 

[OzFab]

My cousin is engine builder.

Well, there's an advantage...

If it is a Honda (I've never seen a black Honda), it's definitely worth saving as a replacement is rather expensive; if it's only a clone, well, by the time you get a rebuild kit & bore it, you may as well buy a new engine...

 

[B.M.800]

Well, there's an advantage...

If it is a Honda (I've never seen a black Honda), it's definitely worth saving as a replacement is rather expensive; if it's only a clone, well, by the time you get a rebuild kit & bore it, you may as well buy a new engine...

I rescued a gx270 with a black shroud from the scrap yard.

 

[shakey0818]

it's definitely a Honda.

 

[OzFab]

it's definitely a Honda.

Then it's definitely worth saving...