Fuel tank not fitting on 1000S project

[Nessism]

I can't figure out what's going on with the fitment of the fuel tank on my 1980 1000S. The tank seems too wide at the front, there is only about 1/4" of engagement per side with the round puck bumpers on the frame, and the tank seems to stick up about 1/2" too high in the rear - rear mount hole won't align. The tank is sitting down on top of the rubber frame pad in the rear so I don't think it's hanging up underneath anywhere.

The bike was in poor condition when I bought it and I can't remember how the tank fit before I stripped the bike down. It wouldn't surprise me if the tank wasn't even bolted down in the back but I found all the hardware so not sure what's going on.

The tank I have looks like a 1000S tank and it has a no-lever petcock that mounts at the rear. The frame likewise looks correct with the rear set pegs and all. With all the monkey business that I've found on this bike it wouldn't surprise me if something funny is going on but frankly I can't figure out what it could be.

Logical answer points to the tank being wrong for the bike, but if this tank is from a different model, which one? Does anyone know what the differences are between the 1979 and 1980 GS1000 tanks?

Any suggestions on what to check? I'm stumped.

 

[newgsman]

not a suzuki pro, but pretty sure the tanks are differant. they had two or three seperate tanks on the various "gs1000" bikes in 79'. and in 80 they show a differant part # which tells me differant tank. hope this helps. looked up info at babbits

 

[hampshirehog]

Ed, can you measure. I've got a SN tank on my 79 S (currently off so I could check real easy) and I've also got an ST tank in the loft. Both have the leverless fuel tap (well should have - now junked in favour of Pingel). I've never noticed any difference between them and we swapped these tanks around in the dealership 30 years ago, but I'll check if you want.

 

[Nessism]

Ed, can you measure. I've got a SN tank on my 79 S (currently off so I could check real easy) and I've also got an ST tank in the loft. Both have the leverless fuel tap (well should have - now junked in favour of Pingel). I've never noticed any difference between them and we swapped these tanks around in the dealership 30 years ago, but I'll check if you want.

Thanks for the offer to help hogman.

Here in the US, the '79 model year 1000E/S had VM carbs and the large handle petcock. For 1980 these bikes received CV carbs and the odd ball lever-less petcock. My understanding is that the petcock is shorter in order to clear the carbs, and on some model bikes, the petcock was relocated on the tank as well - not sure if it was forward or backwards.

I'll take some photos tonight and post them up so you guys can see what I'm fighting against. I'm befuddled.

 

[tkent02]

Thanks for the offer to help hogman.

Here in the US, the '79 model year 1000E/S had VM carbs and the large handle petcock. For 1980 these bikes received CV carbs and the odd ball lever-less petcock. My understanding is that the petcock is shorter in order to clear the carbs, and on some model bikes, the petcock was relocated on the tank as well - not sure if it was forward or backwards.

I'll take some photos tonight and post them up so you guys can see what I'm fighting against. I'm befuddled.

Not sure if the S is the same, but 1980 GS1000E tanks had the same aft petcock location as the 1979 and previous, with the small petcock to clear top of the carbs. 1981 GS1100E tank fits the same with the petcock located between the carbs and head, there is room there for the bigger petcock with the lever which they changed back to at the same time.

 

[bwringer]

If the tank's too wide at the front mounting pucks, sometimes it's because someone tried to remove a dent using air pressure.

This is one of the oldest motorcycling urban legends, but every so often someone actually tries it. The tank spreads out, and the dent usually remains.

 

[KiwiGS]

I have a 1000ST tank I can measure if you would like.
Cheers

 

[Nessism]

Brian may be on to something with the air in the tank debauchery. The tank is definitely too wide in front and the tank is sitting up in back as well - looks like maybe the area on the tank where the rear mounting pad contacts is puffed out but not sure. I posted a bunch of photos in my GS1000S photo album (linked in my signature). Please check them out and let me know what you guys think.

 

[Nessism]

 

[Nessism]

Just had a thought...I stripped out a failed Kreem job inside this tank and then derusted it. To keep the chemicals inside I plugged the tank and there was definitely some pressure inside - although not super high. The tank must have bulged out during this process.

 

[tkent02]

My brother used air to undent a Yamaha 125 tank, it never fit right again.
I wonder if a little vacuum would fix it? Probably not but it might be worth a try.

 

[Nessism]

My brother used air to undent a Yamaha 125 tank, it never fit right again.
I wonder if a little vacuum would fix it? Probably not but it might be worth a try.

Was thinking about vacuum too but not sure how to generate enough to suck in the sides. I think the tank can be pinched in at the front and the bottom can be messaged with a rubber mallet but a more elegant solution would be nice. At least we figured out what happened.

 

[tkent02]

Was thinking about vacuum too but not sure how to generate enough to suck in the sides. I think the tank can be pinched in at the front and the bottom can be messaged with a rubber mallet but a more elegant solution would be nice. At least we figured out what happened.

Couple thousand strokes on a Mighty vac should do nicely.

 

[salty_monk]

Ed,

Does it sit down without the rubber block at the back? Are you 100% sure you have the correct rubbers at the front?

Just some obvious things you prob already thought of.

Dan

 

[JTsGS650]

Was thinking about vacuum too but not sure how to generate enough to suck in the sides. I think the tank can be pinched in at the front and the bottom can be messaged with a rubber mallet but a more elegant solution would be nice. At least we figured out what happened.

I think I would try ratchet straps before vacuum pressure. Whatever method you try, good luck.

 

[Nessism]

Ed,

Does it sit down without the rubber block at the back? Are you 100% sure you have the correct rubbers at the front?

Just some obvious things you prob already thought of.

Dan

Hey Dan,

Unfortunately, the rubber mounts are all correct. Upon further review the tank is definitely pooched out.

Tried to pinch in the sides in front but it?s not going to be easy. I?m surprised so much deformation could occur by out gassing of the cleaning materials. I?m going to explore pulling a vacuum on the tank and then physically messaging the metal at the same time to improve the fit. The outside looks okay to me so it?s just a matter of making it fit better.

 

[rustybronco]

Ed, just a thought to help think the problem out...

clamp the pinch welds on the lower side of the tank with two pieces of oak (one per side), by taking a straight router bit the width of the pinch weld and following the curvature of the tank. you may have to router the slot deeper, then adding bolts to create additional clamping force.

next, bore holes into the "clamps" to allow two or three metal rods to be inserted so the clamp will stay upright and move parallel to each other. lastly drill additional holes to allow threaded rod to be added, allowing the "clamp" to be closed.

"bash" away where necessary, on the underside of the tank, on the metal that may have "expanded".

I liked the idea that was proposed using straps around the tank. but I don't know if it will create more damage than you will be trying to undo.

 

[salty_monk]

Ed let me know if you need some additional brute force... I have some I can lend you

 

[Dreef1999]