Investigating reasons for not starting after sitting and have rust in the gas tank?

I went to start the old gal after she sat for the winter and no fuel was flowing. After testing a few things, I put a gentle air blast up into the tank and fuel flowed for a moment.
Then i went to pull the plug of the petcock and it had a healthy bit of rust in it (see pic). Tank was nearly full all winter which points me to a couple things:
1. This might explain why the reserve setting on the petcock never seemed to do anything (I discovered this the first time I ran out of gas). The area of the reserve intake is probably buried in rust. Does that sound possible to everybody?
2. There are lots of posts on cleaning and sealing a tank on here. Some are old, some are recent. I was looking for a gasket set if I’m going to remove the petcock, but is there a gasket for the petcock-to-tank interface? I see nothing in the parts list.
Cheers.

 

I don’t see a gasket for this spot.

 

Judging by what is in the shit trap, the petcock is likely full of crap and plugged in the reserve circuit. Get the tank emptied and flush out with some gas and see what you are dealing with before talking about sealing.

The area you circled is sealed by the vacuum diaphragm that has two built in "o-rings" on it. One to seal to the petcock and one to seal the back plate.

#5 is the o-ring that seals the petcock to the tank.

The petcocks are not "rebuildable" and the selector plate is riveted. There are kits on eBay with the inner seals and you drill out the rivets and drill/tap the holes to take screws. Make sure you get the correct style as 84/85 are different than 86.

 

rust not just in the gas tank, your carbs will likely need cleaning.

 

Appreciate that. I’ll give your suggestion a whirl and report back (probably after I get back from a business trip)

 

Luckily I have a second set of carbs that were recently rebuilt that I haven’t installed yet

 

Curious in a situation like this, if a second visible fuel filter would be useful to see the rust/contaminants and also keep them out of the carbs...

 

84/85 already has one. 86 is tough cuz it's gravity fed with a very short, tight run to the carbs

 

This has the secondary filter and I don’t see anything in it. I haven’t drained it fully, but it appears clear.
I pumped all the gas out (as best as I good) and I didn’t see any matter going through the clear tube.

 

Might be good news. I would continue verifying the tank and get started rebuilding the petcock. But that sediment came from somewhere...

 

Father Honda still sells the petcock assembly.
16950-MB2-013

 

That number does not match any of the options when you run a parts search.

https://www.babbittsonline.com/oemparts/a/hon/505405e7f870021c54becb0a/fuel-tank

Intakes are totally different

 

Sorry, I was under the impression that this was for an '86. My bad….

 

it looks pretty clean in there. I was able to scrape away a little dust, but nothing like what I saw in the trap. If I put it in On and Reserve positions and blew through the outlet, air would flow freely out the top.

that said, the OEM screen set filter that brings gas’s into the tank was not there and somebody had just put a length of PVC on there.
That seems to be why I would run out of gas sooner than I anticipated, regardless of the reserve. Instead of a stem that brings gas in throughout its entire length, it would only bring it in through the top. I feel so dumb.
Borescope arrives tomorrow. I’ll get a detailed peek into the tank from both directions. And I’ll flush all the lines in case something has worked its way though a hose.
The quest continues!

 

No worries. Seems that people swapped tanks freely as I have another 85 that came with an 86 tank.

 

Thinking more about the intake “filter”. Perhaps the thought of the previous owner was to get the inlet above the gunk. Still strange that that I haven’t seen any sediment in except in the trap.

 

Even more info (sorry to spam the thread):
I was looking at another 85 tank and noticed a difference. So I grabbed the needle nose pliers and pulled out the actual filter and gasket. The previous owner had inserted that other intake into the filter. Perhaps the tear had caused them to do it, but it seems like a seriously stupid fix (unless the originals had a tube inside the filter, which I doubt).
After pulling that and doing some more sloshing and draining, I did get about a 1/2 teaspoon of gunk. Definitely enough to choke up the reserve circuit.
I think after a borescope inspection and the new gaskets and filter are installed I’ll put some clean gas back into it. Because the Reserve circuit was clogged and the most of the filter was closed off by the second tube jammed up it, I guess it’s safe to say that the gunk/sediment has essentially been there for ages and could not have been pulled through the intake.
I’ll report findings next week.

 

Only able to utilize 1/3 of the intake. Thats why I ran out of gas sooner than expected.

 

It is possible that a previous owner filled the tank using a rusty portable gas tank, or a private yard tank that was the source of the sludge.

 

Yes, the originals have that tube. That's how "reserve" works on a petcock that's not full of shit.

"ON" pulls gas from the top of the tube and there is screen right there. Switch to "RES" and it pulls gas at the bottom next to the tube and there is screen there too. Or was.

Towards the top of the tube, on the inside of the strainer, there is a rubber seal on the inside to stabilize the strainer tube. Or was.