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Bill Harris 10-22-2012 03:00 PM

fitting a /6 tank to a /5
I have a used 6.5 gallon /6 tank that I want to use on my old /5 for travelling (the smaller 4.5 gal Toaster Tank is stylish, but more gas is better).

It ought to fit but isn't. It just barely doesn't. The two rearmost lower inside flanges of the tank contact the two sides of the frame rearward of the backbone and won't let it drop down onto the M6 mounting studs. Same width exactly at that point as the Toaster Tank.

At the front of the tank, the top lip above the front tank mount contacts the head bearing dust cap. Again, just barely (maybe less than 1/8") but enough to not let it drop down onto the front mount and slip forward to the rear can drop down. Easy to see why-- the bigger /6 tank is p'haps an inch of more higher in the front. These tanks have always fitted, though it's a tight fit. I guess it's our old foe, Tolerance Stacking.

What to do? My first thought is to get socket and use it as a dolly and gently hammer the front curved area / lip back a little for more clearance.

But before resorting to blacksmithery I thought toss it out to the collected wisdom... :eek1


Big Bamboo 10-22-2012 03:24 PM

Tanks a Lot
I had a similar problem with a similar tank. Try putting it on with the rear too far forward and down as far as it will go and the front up at about 45 degrees, then move it to the rear while dropping the front, without trying to get it on the back mounts on the first try. If that doesn't work, I'd try spreading the two rear edges before I went hammering on the front...

Bill Harris 10-22-2012 04:16 PM

That dawned on me as I was riding this afternoon-- I'm so accustomed to the Toaster tank which must slide in at a low angle that the /6 tank might want to start in at a steeper angle, then drop down. I may have disremembered that trick.

I'll play around with it after dinner.


Big Bamboo 10-22-2012 04:24 PM

Also, I had to remove the steering damper on mine to get it past the top brace.

Bill Harris 10-23-2012 06:29 AM

I played around with it a bit last night. I'm coming down with that flu-bug going around so I didn't get much done.

I looked and compared with the Toaster tank, and I think that teh reason it's not going in is that there is interference between the front top lip and the head bearing dust cover.. So I went back to Plan A and using a large socket as a dolly adjusted that front top lip to give a little more clearance. That worked-- it wants to drop in now, but there is some interference between the Hannigan fairing rear mounting bolts that needs to be addressed. I'll remove the fairing and continue tweaking the fit of this tank.

Such are the perils of progress... :)


photorider 10-23-2012 08:34 AM

FWIW, I have both tanks for my /6. The small one drops in "front first" no problem, while the large one goes in "butt first."

Bill Harris 11-10-2012 10:14 PM

The new tank is ready to install. I ended up having to reshape the front lip for clearance and spreading the rear to clear the frame. BY "spreading" I mean just that-- I put a scissors jack in the rear and pushed the "saddle" apart by not quite 1/8". Did the trick, ithe tank drops right in.

Two things: The interior of the tank is cherry. No rust, factory coating seems intact. I don't expect that a 40 year old factory tank liner will work well with our new Ethanol-laced gasoline, so I'm going to thoroughly clean and skuff the existing tank liner and put an ethanol-proof tank liner in.

Second item: the tank came with a /5/6 flip-top gas cap, the "fancy" locking type. No key. The height of the locking-mechanism will interfere with my tank bag, and I'd like to get non-locking latch button for it. Anyone got a dead/busted/bad /5/6 gas cap that they could rob the latch button off of? I'm just now starting to put out feelers for one.

This is the type cap I have:

Progress. An uphill climb, but worth it...

Bill Harris 11-15-2012 10:00 AM

Progress thus far:

The tank smelt of old gas so I let the interior soak for a day with Acetone, with occasional sloshing. This removed the gasoline residue and revealed a couple of places on the bottom, near the front of the tank where (apparently) old gas & water had collected and the factory tank coating had failed and lifted.

The next step was to agitate the tank with a pound of drywall screws inside. Manually. My arms and shoulders are still sore. :cry This scuffed the interior of the tank and removed any loose tank coating. The only spots where loose coating was removed were at the two low areas in the front and along sharp edges of the welded seams.

The last step in cleaning is to soak the tank in a paint stripper containing Methylene Chloride for a couple of days, with occasional sloshing. This is strong stuff, but the factory liner seems to be holding up thus far-- it's pretty tough. I'm not expecting the factory coating to come off. Then rinse with acetone, skuff with drywall screws and rinse thoroughly again. Then let dry for a couple of days. However, being Winter, I may wrap it in a electric blanket for a day or so and call it dry.

Since the factory coating is still largely intact and since wither of the one-component urethane tank sealers are rated to go over old tank liner, I plan to use the Caswell Plating epoxy tank liner which is a two-component mix that can be used over old tank liner.

Then wait for the next warm spell, apply the tank liner and let it cure for several days.

I have new gas cap leather seals and Karcoma right-angle petcocks, with filter socks, on the way and I should be in business.


Big Bamboo 11-15-2012 10:05 AM

I've heard regular household vinegar will remove the old liner, but I've never tried it myself.

US_Marshall 11-15-2012 10:16 AM

You might want to try a alcohol rinse before drying, it should help remove any left over water and dry faster.

I'll have to try the vinegar on mine.

melville 11-16-2012 06:14 PM


Originally Posted by Big Bamboo (Post 20050664)
I've heard regular household vinegar will remove the old liner, but I've never tried it myself.

You heard about it from me! And it works:

A little floating on top, and a bunch of it sunk to the bottom.

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