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gas tank differences 1979 - 1980 550E

  • Thread starter Thread starter stecz
  • Start date Start date
S

stecz

Guest
This is pretty esoteric... I bought a 1980 GS550 recently and I'm noticing that something is up...

Are there differences between the 1979 and 1980 tank? Right now, the fuel petcock (where the fuel line come out) hits the top of the carb. Now keep in mind, I don't have any of the hardware to bolt the tank down, (just ordered it) and that could solve this problem. But I still believe the tank is the wrong tank.

The reason I think that is I bought a new fuel petcock, thinking that the one I have is wrong for my bike (the petcock hits the carb when you turn it also). So I got one for a 1980 and unfortuneately, it won't attach to my tank. On the 1980 fuel valve, the inlet on top is right in the middle of the valve and on the one I have, the inlet is offset.

Any ideas?

Also, If I buy another tank off of ebay or something, will the door assembly from a 1979 (assuming that's what I have) work on it?
 
If you had a good picture of the petcock, I could help you understand which one it was.

I think the tank was the same on the 550's through 82, unless they got a little more square on the sides like the 1000 tanks did in 1980. The petcock for 1980 did not have a valve, I thought. Can you turn yours to prime, on, and reserve?

I thought I had a closeup of my tank somewhere, but you can see the shape here of a 78/79 tank:

New%20Cafe%20Fairing%205-27-05%20003.jpg


~Adam
 
I have a 80 550E.
I bought a tank from a '78 and had the same problem. The tank itself is the same. The carbs and the petcock in '80 are differant.
Take the petcock from '80 you got. Take the four screws off the back and turn it so the vacume line faces forward. (I had to do that to make mine fit too) Does that fix the problem? Do you have pictures?

Yes, the fuel door will work.
 
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There is no petcock in this picture but...notice the carbs on mine compared to AOD's (EX) bike.

9203b6ed.jpg


Is this the problem you're having? (note '78 petcock inlet on top of carb)
RatBike001.jpg
 
yes, the problem on that last picture is the problem...

But, you can't bolt the '80 petcock into my tank. The inlet tube and filter thing is in the center and mine is offset.

The problem is that on the petcock I have now, the outlet to the carbs hits the top of the far left carb. It's close enough in there that I think that maybe I can just raise the back of the tank up very slightly and it won't hit anymore. Once I get the tank mounting hardware, I should be able to see.
 
stecz said:
yes, the problem on that last picture is the problem...

But, you can't bolt the '80 petcock into my tank. The inlet tube and filter thing is in the center and mine is offset.

The problem is that on the petcock I have now, the outlet to the carbs hits the top of the far left carb. It's close enough in there that I think that maybe I can just raise the back of the tank up very slightly and it won't hit anymore. Once I get the tank mounting hardware, I should be able to see.
Click to expand...

You may need to simply get the '80 model screen to make it all work out.
Any photos?
 
stecz said:
yes, the problem on that last picture is the problem...

But, you can't bolt the '80 petcock into my tank. The inlet tube and filter thing is in the center and mine is offset.

The problem is that on the petcock I have now, the outlet to the carbs hits the top of the far left carb. It's close enough in there that I think that maybe I can just raise the back of the tank up very slightly and it won't hit anymore. Once I get the tank mounting hardware, I should be able to see.
Click to expand...
I didn't realize there would be a problem! I wanted to keep my original colors on my 1980 550E so I bought a 1979 tank. Hadn't gotten around to doing anything with it but took a look and your right!

I looked up the 79 and 80 petcocks at crotchrocket.com and they are different. The carb diaphram covers are bigger on the 80 and thats your problem, the fuel outlet hits the carb.

Here is the deal. The 80 fuel tank has a long slot between the two bolts. It looks like either petcock would work. However, the 79 fuel tank has a short slot, just big enough for the offset filter, and the slot is closer to the rear bolt.

You'll have to do what I'm going to have to do to use the older tank. It looks like you can use a dremel tool with a cutter wheel on it to lengthen the slot toward the front bolt. I can't tell if it would need widening also right now, but it might need to be a little wider. You really only need to go far enough to let the 80 petcock filter go up in the tank. I would probably use the 80 O-ring also. It doesn't have the cross pieces built into it.

If you do this, make sure and wash it out well with either gas or kerosene to get all the metal stuff out of the tank. A small magnet would probably be a good idea before washing.
 
I had a duh moment and decided to do exactly what you just said.... Since the 80 0-ring (they aren't interchangeable) is just on the outer edges, it shouldn't cause a problem, it also looks like the '80 petcock wont' hit the carb on my tank either... I'll mock it up tonight....
 
78/79 is definitely what I have...

I looked at putting the 80 petcock on, but it won't work, not only is the strainer in the wrong spot (nothing a little grinding wouldn't fix), but the vacuum diaphragm hits the tank. That could be fixed by dimpling the tank, but then I would probably distort the mounting surface and the petcock would leak...

so, I think I'm going to modify the rear mount to raise the rear of the tank 1/16 of an inch or so and it should be fine...

maybe someday, when the rest of the bike is near perfect, I'll find an 80 tank and install that...
 
stecz said:
78/79 is definitely what I have...

I looked at putting the 80 petcock on, but it won't work, not only is the strainer in the wrong spot (nothing a little grinding wouldn't fix), but the vacuum diaphragm hits the tank. That could be fixed by dimpling the tank, but then I would probably distort the mounting surface and the petcock would leak...

so, I think I'm going to modify the rear mount to raise the rear of the tank 1/16 of an inch or so and it should be fine...

maybe someday, when the rest of the bike is near perfect, I'll find an 80 tank and install that...
Click to expand...
Are you sure it hits the tank? I don't have an extra 80 petcock, but the mounting looks like it should work fine on the 79 tank. It may be close to the tank, but so is the 80 petcock on the 80 tank.
 
By the way, where did ya'll get those fairings? They look sharp. I also like the lower fairing.
 
DCP03371.jpg
DCP03371.jpg

This is what a 80' petcock should look like.
 
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The 80 definitely won't work, you can't tighten the bolts, if you do you would probably crack the body of the valve.

The bolt pattern is the same between the two valve, but they fit the tank differently.

On the 79 petcock, the other think I had to do was trim the end of the lever off because it hit the top of the carb. (mine now ends at the circle).
 
8trackmind said:
DCP03371.jpg

This is what a 80' petcock should look like.
Click to expand...
That isn't what mine looks like. On mine the fuel line comes straight out of the back at the bottom and the vacuum line comes out up higher and points forward.

I'm going to try and get my camera working and show some pictures.
 
stecz said:
The 80 definitely won't work, you can't tighten the bolts, if you do you would probably crack the body of the valve.

The bolt pattern is the same between the two valve, but they fit the tank differently.

On the 79 petcock, the other think I had to do was trim the end of the lever off because it hit the top of the carb. (mine now ends at the circle).
Click to expand...
I'm going to have to take my tank off. Looking underneath it, I think I see what you mean. It looks like the 80 tank is just a bit more narrow where the petcock is and will let the vacuum module clear it.

Like you said you would have to dimple the 79 tank to get it to clear. I need to sync my carbs so I'll pull the tank and verify that.
 
Here is the best photo of the 79 tank.

petcock5.jpg


Here is the best photo to see the difference in mounting on the 80 tank

petcock4.jpg


And here is a good photo of the 80 petcock

petcock3.jpg


8trackmind - my 1980 GS550ET petcock doesn't look like yours!
 
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