GTS-1000A Fuel Tank Mods

Launched: 12/08/2002      Updated: 03/01/2003

GTS-1000A Fuel tank modifications, why and how
(click on each photo to enlarge)

While the GTS-1000A is a magnificent bike, it does have little idiosyncrasies that pose challenges. Not the least of which is the fuel tank, most notably the flapper in the filler neck. As most who've ever fueled a GTS knows, it can take up to a dozen "burps" to get the tank full. This is due to the constrictive neck and flap keeping the air from escaping to allow more gasoline into it.
The fuel tank neck/flap

Okay, we all know why it's there in the first place- To keep people from putting leaded gasoline into it. Since the GTS has a catalytic converter, it's not very tolerant of lead. But realistically, how many gas pumps have leaded gas anymore? None that I'm aware of. So since this thing isn't really useful, and it only gets in the way, let's get it out of the tank and make fill-ups faster and more complete. It's not hard, and it's not really all that time-consuming. Start this project when you have under a gallon of gas in the tank, and you have an empty gas can handy.

The first thing to do is to remove the top and side bodywork to allow us to access the tank. Then remove the lines connected to the tank, and the wires connecting the fuel pump and gas gauge sending unit. Don't turn the key on before you disconnect the wires! If you do, the fuel pump will spray gasoline everywhere. How do I know this? I stupidly turned on the key for a moment to see what the level in the tank was, and both Dave Biasotti (without whom these modifications would not have been nearly as fast and easy) and I got sprayed.

Neck/flap from the inside

Once everything's disconnected from the tank, remove the tank itself. This might be easier said than done- The two long flange bolts at the front of the tank tend to strip their threads. One of mine did. and I had to cut it in half with a dremel to get it out. Many hardware stores may carry this exact bolt, so you don't have to get it from Yamaha. Fortunately it's the bolt that self-destructs, and not the threads in the nuts welded to the frame. Just in case, I ran a thread tap through the nuts to make sure their threads weren't damaged.

After the tank's out, remove the fuel pump and the fuel level sending unit. Be careful not to bend either of the units, and don't damage the rubber gaskets- You'll need those again when reassembling.

Chafed wire shield/insulation
Speaking of the fuel level sending unit, check it carefully- It might have a problem. It seems the bracket for the unit has a hole in which the wires pass through. This hole is rather sharp, and can cut through the rubber shield and wire insulation causing a grounding of the current. This will make the fuel gauge behave strangely. The insulation was cut through on Dave's bike, which made the gauge jump up to "full" when the tank got down to half full. This is because the wires would move with the float inside, and eventually touch the metal when the fuel level dropped. As you can see in the photo, only my shield was cut through, but had I not taken care of it, I'm certain I'd have had the same problem that Dave had. We'll cover the fix for this problem after we finish the tank.

Bag taped around filler neck
With the tank out and pump and sending units out, you must empty the gas into your gas can. Let the tank dry well. Blow it out with compressed air if you can. All of the fuel vapors should be gone before you start cutting the metal. Take a plastic bag and tape it around the filler neck on the inside of the tank. The object here is to seal the bag as high around the neck as possible, so that when you cut off the neck all (or most) of the metal shavings are caught by the bag. As you see in the photos, I did a marginal job. The smaller your hands are, the easier it is to work inside the tank.
Use Dremel to cut neck out

Once the bag is in place, it's time to cut the neck out. Use a Dremel tool, preferably one with a flexible drive line. This moves the cutting bit far away from the motor, allowing a lot more control over the cutting, and it lets you get into much tighter areas for cutting. If you haven't got a Dremel, get one. Don't put it off- It's a remarkably useful tool for cutting, shaping, sanding, and polishing. It's one of the most useful tools I own.

Tank without the neck/flap
When you taped the bag onto the inside of the neck, you should have taped it higher onto the neck than your cut will be. I just launched into cutting the neck, making a slow cut all the way through. Dave gave me a tip after I'd pretty much finished- Rather than cut through immediately, keep grinding away all the way around slowly, a little more each pass. The more you can cut away without going all the way through, the more filings the bag will catch. It'll also be easier on the cutting disk, and you'll use fewer disks. A lesson I'll
The neck inside the bag
know for the next time. When you finally cut all the way through, the neck will fall into the bag. Or, if you taped too low like I did, the whole bag (with the neck inside it) will fall into the bottom of the tank.

Remove the bag from the tank without spilling the filings. If you did it right, you'll have no filings in the tank! However, if you did it like I did, you'll have a big mess to clean up inside. I shook out as many filings as I
Metal filings caught by the bag
could, I used compressed air, a magnet, anything I could think of to get all the filings out. But they just wouldn't leave. So I got a rag, poured a little of the saved gasoline onto it, and used that to pick up all the filings in the tank. That worked pretty well; I think I got everything out. But I'll change my fuel filter soon to make sure. Oh- This is a good procedure to do BEFORE you change that expensive filter!

As you see from the photo, the bag DID catch a lot of metal filings, even though I didn't tape it as well as I could have.

Now for the fuel gauge sending unit. I was lucky- the sharp edge of the bracket had only cut through the shield, not the wire's insulation. But I thought it'd be a good idea to make sure the problem doesn't get any worse.
Wires unsoldered

Original sharp edges
First I unsoldered the wires from the mounting bracket. Then I pulled the wires through the offending sharp-edged hole. Using a grinding bit on the Dremel and some fine-grit sandpaper, I smoothed the edges of the hole in the bracket. After the hole was smooth and not likely to chafe the wires any longer, I wrapped the wires in electrical tape to keep them a little safer. Writing this, I've had a chance to think a little more about the operation, and I started to wonder how well electrical tape adhesive will hold up in a tank of gasoline. I now think a better fix will be to use
Smoothed edges
heat-shrink tubing. Dave agrees with this, and suspects that my tape is already floating freely in the gas tank by now. So I'll go back in to change it out. I'll update this page to let you know just how well the tape did (or did not) work.

If your insulation is chafed to the point of exposing the wires, I'd definitely suggest you use heat-shrink tubing, or even replace the wires entirely. Even if you replace the wires, I'd still recommend putting heat-shrink tubing over them as an added precaution against wear. This may be a bit of overkill, but I'd rather do that than risk having to go in to fix it again. (well, I do anyway, but YOU don't!)

Completed wire fix
The last thing to do is to rethread the wires through the (now smooth) hole, and resolder the connections.

Now it's time to reassemble everything. Mount the fuel gauge sending unit and fuel pump back into the tank. No sealant is needed for the rubber gaskets. Make sure that the mating surfaces are clean, so the gaskets will seal. When mounting the fuel pump and sender flanges - tighten in a cross pattern like any flange union so as not to warp it and once tightened this way, go around and tighten a second round. Don't torque the little bolts down hard- You don't want to crush the rubber seals.

Remount the tank assembly onto the frame, taking care not to strip the threads on the mounting bolts. By the way, the long (top bolts) are only 10 mm and don't need much torque as they are only holding the tank front to rear. You may have to loosen the 'U' bar brace in front of the tank to get the holes to align. Reconnect all hoses and wires. Pour your saved gasoline back into the tank, and then turn the key on. This will charge the fuel line with gas, and any leaks will be noticed immediately. If it's clean and tight, go ahead and replace the bodywork, and you're done!

Go to a gas station and fill the bike. You'll be amazed how much easier and faster it is to get a full tank. I mean, REALLY full. Unless you're used to spending the time and effort to burp all the air out of the tank, you'll get about another half gallon into it. Dave tells me that filling the bike on its centerstand will allow a bit more gas in than if you fill it on the sidestand.

Update 03/01/2003- I replaced the tape with heat-shrink tubing

It's been a few months since I'd done the above operations. And all that time, there's been a little nagging voice in my head saying "You know, you really do need to check out that electrical tape and see if it's a problem."

Seeing as how I always feel better when I pay attention to those nagging voices (if only to shut them up), I broke out the tools again and pulled the GTS apart.

The tape's in place...
Sure enough, there was an issue. No, it wasn't catastrophic, but it was about what I expected. The tape was still in place, but it was clear that the tape's sticky adhesive was gone- dissolved by the gasoline. With any luck it hasn't taken up residence in my catalytic converter. I suspect that it was diluted tremendously, and has burned completely away, seeding the clouds for some oddly-colored rainfall. Since the tape was wrapped tightly around the wires, and then shoved through the bracket hole, it really couldn't unwrap itself and fall off. So while there was no "stickum" holding the tape on, it was still doing its job of shielding the wires from the bracket.
...But the adhesive's gone

The plan was to remove the tape and cover the wires with heat-shrink tubing. It's durable, impervious to gasoline (as far as I know), and cannot unravel. I thought about replacing the wires entirely, but decided against that for two reasons. First, they'd be fine as they were. Since the tape without any stickum still protected them, and the bracket had been smoothed, I didn't see any risk of further damage. Second, it's possible that the wire I'd use to replace it would be of different resistance than the original. It may not be likely, nor might it be significant, but why risk it?

Solution: Heat-shrink tubing
My solution for putting on the shrink tube was probably overkill as well- I put one small diameter piece on each of the wires. This would probably be sufficient to protect the wires for the next century. But I didn't stop there- I added a slightly larger piece, which fit over BOTH of the wires. You can see the small pieces just sticking out of the larger piece.

I re-soldered the wires back in place, mounted the sending unit back into the tank, and buttoned up all of the bodywork.

Note that I did all this with a very empty tank. I didn't feel like taking the tank back out again. I suspect that having a tank less than half-full would be fine, but I figured that the smaller amount of gas there was, the less chance I'd pull it out when removing the sending unit. I'd prefer to not spill gas on the bike.

So there you have it. Three months after the first operation, the tape was replaced. We've learned that gasoline really will degrade electrical tape, and probably in a short amount of time- My GTS has been sitting in my garage with an (almost) empty tank for a month. I can't say how long it took for the gas to eat away at the tape's adhesive, but it probably didn't take long at all.

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