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Will a Gen4 gas tank and seat fit on a Gen3?


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Trying to explore options for a gas tank and seat for my 91. The eBay Gen3 gas tank was a bust, the seller didn't pack the box up properly and it arrived damaged. Gen4 gas tanks are more readily available as well as the Gen4 seats. The gas tank mounting tabs look to be the same as Gen3. Is it possible to swap the gas tank and seat from a Gen4 to a Gen3?

Just a recap, my 91's gas tank is badly rusted inside, rendering the petcock and fuel level sender completely unusable. The gas tank will need long therapies of electrolysis to clean up, which I will attend to. I was looking at eBay used gas tank hoping to find one that's not rusty and with a petcock and fuel level sender(I know it is available new). Looking at a seat as well because I am very short legged and need to shave the seat. I would rather not shave my original seat that is in good condition.

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I happen to have a 1990 and a 1995 with all the bodywork off right next to each other in my shop.  I'm not optimistic.  The mounting styles are similar, but the way they mount it has to be EXACTLY the same.  The mount locations are all the cast aluminum portions of the frame.  Now bring in a seat and there's even more variables.

 

No 4th gen came in the same red as the 3rd, so you would have to repaint.    So if the tank you got is clean, why not bite the bullet and have it fixed and painted? 

 

Your bike deserves to not be a mash up.  It's fucking nice.

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2 minutes ago, Captain 80s said:

I happen to have a 1990 and a 1995 with all the bodywork off right next to each other in my shop.  I'm not optimistic.  The mounting styles are similar, but the way they mount it has to be EXACTLY the same.  The mount locations are all the cast aluminum portions of the frame.  Now bring in a seat and there's even more variables.

 

No 4th gen came in the same red as the 3rd, so you would have to repaint.    So if the tank you got is clean, why not bite the bullet and have it fixed and painted? 

 

Your bike deserves to not be a mash up.  It's fucking nice.

 

I always keep my bikes original or with original parts as spares if I am modding it. It's another reason why space is an issue with a limit of 10 bikes 😂 The original gas tank will be de-rust, it is just going to take some time before it is done. I totally agree with not mashing it up. It is the riding itch talking here 😅. I am just trying to solve the gas tank and petcock dilemma with more options quickly so I can ride it.

Since I got the bike fairly cheap, I could bite the bullet and buy a brand new gas tank for $600 but I would still need a working petcock to ride. 

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2 minutes ago, Captain 80s said:

Have you drilled out the rivets and opened the petcock? (I forget)

 

Yes, the pivot shaft is badly corroded and does not provide a seal even with a rebuild kit. I guess last resort I can try to JB Weld the shaft and grind it back into shape but how long will take work with gas?

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Long enough to come up with your next solution while you ride it.  And the fuel pump is back down below the carbs, as long as it's not leaking out the face it doesn't matter if it won't shut of all the way.  There is no way your gonna gravity-push fuel through the pump and back up hill and then overcome the float valves in the carbs.

 

Put a high quality fuel line quick-disconnect for when the tank has to come off.

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4 minutes ago, Captain 80s said:

Put a high quality fuel line quick-disconnect for when the tank has to come off.

 

That is one of the options to overcome the leaky petcock. Saw a post on here with one that fits.

In the meantime, I am looking on eBay and other selling sites. If anyone is selling a R157 gas tank with petcock or just the petcock please let me know. I just need to find enough stay at home time to start the electrolysis where I can keep an eye on it while it cooks

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I know none of those are actually great, but they are the ones with hardware.

 

Would like to see inside the one with the cap.

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10 minutes ago, Captain 80s said:

I know none of those are actually great, but they are the ones with hardware.

 

Would like to see inside the one with the cap.

The problem is I prefer not to repaint or repair dents. At that kind of $$$, I would rather pay the $600 and get a brand new R157 tank.

 

I would be willing to pay for just the petcock but there is no way to know if it is still good

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1 hour ago, DesertKyorugi said:

 

Yes, the pivot shaft is badly corroded and does not provide a seal even with a rebuild kit. I guess last resort I can try to JB Weld the shaft and grind it back into shape but how long will take work with gas?

There have been thousands of cager fuel tanks permanently repaired with JB Weld.  The shaft is a moving part so it won't be permanent, but if you can get it shaped well enough to seal, it will last a while, especially if you aren't turning it on and off all the time or having to hit reserve a lot.  I never turned my little 500 Interceptor off except when I parked it in my apartment bedroom for Christmas break one year, but I did have to hit reserve pretty often. lol

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16 minutes ago, Captain 80s said:

Where can you buy a new tank?

 

I have a friend who works for a parts warehouse. He found a R157 NOS gas tank for about $600 plus tax. I think it is at a Honda dealer in FL

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Think I'd make a fairly thick block off plate (to replace the fuel selector and cover, not eliminate the petcock) and seal it with some 1/32 viton sheet rubber.  Then use a quick-disconnect. 

 

 

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2 minutes ago, Captain 80s said:

I can't believe this thread isn't "Check out my NOS tank" then.

 

LOL, I am cheap plus I haven't ridden this bike yet. The carbs will go on today, I might have the engine running.

 

Also, I have a money pit project going on right now restoring my 70 CB750K0. Just bought the full body kit for it, the $600+ for the NOS gas tank will have to wait since the original gas tank is totally restorable

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20 minutes ago, tbzep said:

There have been thousands of cager fuel tanks permanently repaired with JB Weld. 

JB Weld is right up there with PB Blaster and E6000, and it is impervious to fuel. 

 

Cheapo track repair on creased tank w/out leaks. 

 

I'd get that NOS tank on teh way...packed properly and insured. 

 

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34 minutes ago, Captain 80s said:

I can't believe this thread isn't "Check out my NOS tank" then.


Oof, found a NOS petcock for $129 plus tax and shipping........

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3 minutes ago, Captain 80s said:

You HAVE to buy that Petcock.

 

It is more than twice the cost of an original Honda CB750 petcock but seeing that it is an unobtainium, I went ahead and order it. Hopefully there is no mistake in it being the correct item 🤞

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2 minutes ago, Captain 80s said:

Now that you ordered it, where did you find it?

 

It came to about $150 with tax and shipping 😢. I ordered it through my buddy's connection. He's my source for unobtainiums. I didn't ask where this part was found 

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