Tank Sprang a Leak While in Storage

[Griffin]

Saw a thread that mentioned fuel tank repair. Responded there, but decided to start a new thread about it.

Had a GPZ750 in storage for three years. When you have so many bikes, you decide at the beginning of the riding season whicch two or three you'll ride, and leave the others in log term storage prep. Most of my bikes are in my shop under a king sized bed sheet to keep the dust off them.

Anyway, last month I noticed a slight gassy odor. Very light, but definitely something that had not been there before. I looked under every bike and at every sheet, seeing if I found any evidence of a fuel leak (thinking petcock/tank o-ring or maybe petcock failure had flooded carbs). Didn't see anything, so thought little more of it. A few days later, I go back out to the shop and there's a very strong odor of gasoline. Okay, now I have to find out what's going on. I start removing the dust covers off each bike and going over them ccarefully. I think the GPZ was the fifth or sixth bike I olled at, and saw the problem immediately.

There was a huge blister under the paint/decal area 2/3rds up on the side of the fuel tank, and a yellow streak stain under the clear coat beneath the blister. I poked it with my finger, popped the paint bubble, and gas poured out all over my hand and continued to dribble out after the bubble was empty. Yikes.

After I drained fuel out of the tank to below the leak level, I peeled the paint away and found this:
image.png

Gonna have to strip this down and inspect more ccompletely, I reckon.

[Cipher]

If you're driving daily a quick fix can be done with a loctite product. Forget the name but its a two part epoxy putty.
Perfect for old beater cars but a useful stop gap for bikes.

[Griffin]

Found a basically NOS ‘83 red tank on eBay. I think it’s a dealer take off, there is one tiny dimple on the front side of the tank. Couldn’t resist so bought it.

I received it today, still in the original factory box. I’ll rate it 9.5 out of 10 for condition.

I already have a perfect red fairing thanks to the late George Burroughs (KoolaidKid), who gave it to me after he sold his GPZ750.

I’ll buy a couple side covers, a fender and a tailpiece off eBay and repaint them. Decals are available for those pieces.

I guess my silver 1984 GPZ750 will soon be wearing red 1983 GPZ750 bodywork. Then I can decide how to deal with the leaking tank at my leisure.

[Nessism]

George was a gem. He PM'ed me one day and wanted to send me all his KZ750 valve shims. I didn't understand why at the time, and he wouldn't accept any compensation. They have come in handy over the years, and I think of him every time the bag comes out.

[oldGSfan]

Congrats on the score. I love me a GPz 750. I remember riding a sweet '82 that I found for a colleague, immaculate '82 low-mile I found him as a favor, for under $1K in '99. That engine sang, was smooth, and had plenty of pep. I was always on literbikes due to my height but that bike made me rethink things. I had read all the 750 comparisons and it always did well due to its overall weight / HP / handling balance. I still think it's the best air cooled 750 (sorry to be a blasphemer on the GS site)

Would like to see pics of the bike when you have the tank mounted.

[Griffin]

Tom, I have both GPZ750 versions in my garage, sort of. The original '82 GPZ750 was a twin shock, fairly conventionally styled bike for the time, like the original '81 GPZ550 and 1100 models were. They were all modified versions of existing standard models (KZ550A, KZ750E, and KZ1000J) and shared a lot of common parts with the standards they were based off of.

In 1983, the GPZ lineup was totally changed to the nearly identical looking monoshock 550, 750, and 1100 models. The standard KZ550A and KZ1000J stayed in the lineup, but the KZ750E went away, with the '82 GPZ750 replacing it as the standard option, being redesignated as the KZ750L, and also getting the early '80s black with red and orange stripe styling treatment.

So the bike in my garage that's getting the new red skin is a monoshock '84 GPZ750. I have an '84 KZ700A, which is the '83 KZ750L destroked to 699c to evade the new tariff.

So it's basically an '82 GPZ750, but 39cc lighter .

I used to own a red '81 KZ750E. I bought it from George when he was thinning his herd. I ended up giving it to a friend of mine who was my riding buddy in high school. He owned an identical '81 KZ750E back in the day. He had been diagnosed with an inoperable brain tumor in 2008, I gave him the bike in 2009, and he rode the crap out of it until he was too sick to ride in 2012, shortly before he passed.

I really wanted that bike back, but his sister sold it towards the end when he was bedridden and suffering daily seizures. He had previously told her to call me to give it back, but she sold it without his knowledge to someone for $800.

[oldGSfan]

My Air Force buddy bought an '82 GPz750 new, leftover in the summer of '83. The dealer had painted it in the green ELR livery. It looked convincing from afar. Another friend had the standard (called 'Sport' I believe) KZ750 in stock colors, black with red and yellow stripes. I got a leftover '82 KZ1000J. I wanted the ELR but they had none.

I remember the change to monoshock. I am partial to the styling of the '82 by just a bit. I also remember the tariff. I was never cross-shopping an HD with a Japanese bike and it ticked me off. Sorry to hear about your friend, sad story.

[Nessism]

As one might guess, I'm a huge KZ750 fan. After finishing the restoration of my bike, and riding it, I was really struck by how much smaller and easier it handled compared to my GS1000, which shared garage space at that time. When the time came to clear space, the 1000 was set free, and the 750 stayed. The '83+ GPz750 is a more stretched out bike. No doubt, more capable on the track. And better for large riders. For me, though, the bar reach is a bit...much. The GPz bikes have more power, and a rubber mounted engine, to quell vibrations. While my bike is remarkably smooth, I suspect the later bikes would be better on long road trips.

[salty_monk]

Lining that tank with POR15 and painting a bit more on the outside would sort it out. Then paint it as normal.
I did that on my 1000 when it did the same. It’s always the right front corner, the spot that gets emptied when you put it on the side stand.

[Griffin]

As one might guess, I'm a huge KZ750 fan. After finishing the restoration of my bike, and riding it, I was really struck by how much smaller and easier it handled compared to my GS1000, which shared garage space at that time. When the time came to clear space, the 1000 was set free, and the 750 stayed. The '83+ GPz750 is a more stretched out bike. No doubt, more capable on the track. And better for large riders. For me, though, the bar reach is a bit...much. The GPz bikes have more power, and a rubber mounted engine, to quell vibrations. While my bike is remarkably smooth, I suspect the later bikes would be better on long road trips.

The twin shock, four cylinder KZ750/700 models imported from 1980-1984 (they were offered in Europe a few years longer with shaft drive and a sport touring setup) were evolved from the original KZ650. As such, they were much lighter and felt smaller than the 750 class bikes offered by Suzuki and Honda at the time, which had 16 valve engines, not 8. I also have an XJ750 Seca which has a similar "small" feel to it. Yamaha took the same approach as Kawasaki, stroking and punching out their 8 valve XJ650 engine to 748cc.

I call the GPZ my "hooligan bike". It's got K&N pods, Dynojet Stage 3 jet kit, stainless Supertrapp exhaust, and aftermarket cams in it. It's pretty weak down low compared to my Seca, but around 5500-6000 rpms it comes on really hard, more like a liter bike. It really is designed to go around racetracks at triple digit speeds. It's wonderful to ride in 60-70 mph sweepers. The seating position is much more aggressive and low than the other 750s, but I find it quite comfortable.

When I bought my GS700E (now ES) in 1985, there was also a holdover '84 GPZ750. I liked the more upright riding position of the GS better, and it was $300 less, which was a lot of money to a 16 year old kid.

Now I have them both.

[Griffin]

Lining that tank with POR15 and painting a bit more on the outside would sort it out. Then paint it as normal.
I did that on my 1000 when it did the same. It’s always the right front corner, the spot that gets emptied when you put it on the side stand.

It's too cold here to work in the shop, even with a space heater. Once I get a chance to pull it, I'll give it a good look inside and out to see how bad it is.

[rphillips]

Just my 2 cents worth. When I first started fooling with bikes, I was told when storing a bike, fill the tank as full as you can get it with gas. Reason being rust can't form under the gas. Not sure this will always work but I had a GS1000 tank that had been stored, on the bike, in an unheated shed, full of gas for 10 or 12 yrs, when opened, to sell to a GSR member, and poured all the old brown, stinking gas out, it looked new on the inside. Also drained a tank on my KZ1300 and within 3 months inside of tank was completely coated with surface rust.

[Nessism]

POR-15 is good stuff. If the metal is badly compromised, though, I think Caswell's epoxy is better, because it's so thick.