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Discussion Starter · #1 ·
I was draining my tank yesterday to check things out and found it would not drain without removing the petcock entirely. The '81 CX has a diaphragm that won't allow fuel to flow w/o a vacuum line so it makes sense that draining the tank with the selector in the "On" position wouldn't work but is the "Res" position supposed to flow w/o a vacuum?



I guess I'm wondering is removing the petcock normal or is something afoul, and is so, what?



Thanks
 

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It doesn't matter if the petcock is ON or RESERVE, if there isn't either vacuum on the front fitting, or pressure on the vent fitting, the fuel will not flow. So, yours is acting normally.
 

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Discussion Starter · #3 ·
Thanks, that appeared correct when I looked it over but seems a bit ill designed to make you remove the entire assembly just to drain the tank. But not a big hassle so not a big deal.



Thanks again
 

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Thanks, that appeared correct when I looked it over but seems a bit ill designed to make you remove the entire assembly just to drain the tank. But not a big hassle so not a big deal.



Thanks again


It would probably be easier to remove the tank and turn it upside down.


Also if you blow into the vent hose that comes off the petcock or apply suction to the vacuum hose you can drain the tank that way.
 

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The little Suzuki GSX 250 I used to have had a vacuum fuel tap but in addition to 'run' and 'reserve' it also had a 'purge' position that would allow fuel to flow without the engine being cranked.



This was handy if the bike hadn't been run for a while or if you simply wanted to drain the tank.



It's a wonder Honda didn't incorporate this feature into their own vacuum taps.
 

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'82 GL500 '83 GL650 '21 RoyalEnfield INT650
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It doesn't matter if the petcock is ON or RESERVE, if there isn't either vacuum on the front fitting, or pressure on the vent fitting, the fuel will not flow. So, yours is acting normally.
Is this true of the GL500 too?

Thanks!
 

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'82 GL500 '83 GL650 '21 RoyalEnfield INT650
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If you still have the 3 barb petcock yes
Yes, three. I can't remember if it was here or on the antique Honda page on Facebook. someone suggested stuffing rag into the gas tank to "empty" it. I took a long, narrow piece of longsleeve Tshirt and stuffed it in the tank. Dried it completely!
 
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'84 CX650E that is evolving into a GL500
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You could have used a piece of hose and siphoned the fuel out or found a way to apply vacuum to the petcock and wouldn't have ended up with a very flammable rag. I have an old inline primer bulb like they use on snowmobiles that I used to use for that before I changed to a non-vacuum petcock.
 

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You could have used a piece of hose and siphoned the fuel out or found a way to apply vacuum to the petcock and wouldn't have ended up with a very flammable rag. I have an old inline primer bulb like they use on snowmobiles that I used to use for that before I changed to a non-vacuum petcock.
Haha! I'm a potter and have many "flammable" things around. Actually, I used the rag to clean some parts up. Worked well, especially if you don't have hose or a primer bulb. Besides, you couldn't see where the gasoline was to suck it out. The rag filled the tank perfectly.
I do have some bulbs I use for slip decorating, but I don't want to foul those. The rag worked well enough. If the rag is worrisome, just wash it with some detergent. ;)
 

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'84 CX650E that is evolving into a GL500
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Using the bulb to apply vacuum to the petcock through a length of tubing shouldn't contaminate it but I understand your concern. On the other hand, if you ever decide to retire one of the ones you use for pottery save it for working on the bike.

I don't put rags that have been soaked in solvent in the washing machine. I use them up and throw them out or, if I need to get rid of one right away I have been known to lay it on the gravel driveway and light it...

As for seeing where the gas is to suck it out, it will always flow to the lowest point, and on a GL500 that's those silly areas where the sides of the tank hang down to meet the side covers (what a stupid idea that was; they should have made the floor of the tank flat and just extended the sides but nooooo, they had to leave those pockets for water to collect in and eat its way out through the steel).
 

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Yeah ! Stuck in an old long sleeve t-shirt through the fuel cap opening , turn the tank around ( after loosening it from the frame and from the tubes running from the pet cock :) ) , shake it up and let it rest for a long while , then take out the t-shirt and make a bon fire on a save spot.

I have an old faded long sleeve t- shirt I will use next time the tank needs to be emptied . It has an the inscription on the front that reads :

" Normal people scares the hell out of me "
 
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