Correct Fuel Tank Mounting

I'm struggling to figure out which rubber bushings to use for the fuel tank mounting, I've seen the rubber washer variety and I've seen the rubber bushing with the bolt thread coming out of each end - does anyone know which one I should be using on a 1973 Commando Interstate? I've been Googling this like crazy and I haven't been able to find any solid answers.

Branch said:

I'm struggling to figure out which rubber bushings to use for the fuel tank mounting, I've seen the rubber washer variety and I've seen the rubber bushing with the bolt thread coming out of each end - does anyone know which one I should be using on a 1973 Commando Interstate? I've been Googling this like crazy and I haven't been able to find any solid answers.

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The washers. Just bought a set.

http://www.oldbritts.com/1973_g28.html

06-0648 Washer, Rubber, Mounting

Edit: for some reason the image was not displaying - see the link above for the exploded diagram

I use this type of readily available industrial mounts for the bobbins on my bike. The internal thread insert provides greater surface area adhesion so reducing peeling off of the endplates. They come in different thicknesses so muffler angle or tank clearance is better controlled. The button head setscrews (not shown) are easier to engage e.g. for the fuel tank fitment without coil holder clearance issues.

When I first got my Mark IIA Commando I had difficulty understanding how to mount my Interstate tank. The first problem I had was that the parts supplier would sell me the Roadster tank pads instead of the Interstate tank pads. I have since figured out that the rear Interstate tank pad is much thinner than the Roadster tank pad.

The tank sits on the frame in three points - the tank pad on the rear and the forward rubber washers that mount to the frame tabs. As for the front tank pad it serves only as a chafe protector from the frame's top tube. For each forward tank mount I used a stud, three rubber washers between the tank and the mounting tab and then the tank is held down with one more rubber washer and a large area steel washer. The rear of the tank is held down using a steel strap with a rubber pad bonded to it and this is bolted up solidly to the tank using no rubber washers or mounts. The strap with the slotted opening is placed on the right side. The reason for doing this is because the bolt is a little difficult to get to and with it on the slotted side you only need to loosen the bolt to remove the strap.

The 850 Mark III parts book seems to be clearer as to showing how the rear tank strap is mounted however I mounted mine with the rear tank strap slot facing to the right instead of the left.
http://www.nortonmotors.de/ANIL/Norton Website/norton/parts-list.php?Model=n850_e&Plate=030

Last but least, for removing and installing the front hold down nuts I found that using a 1/4 inch drive - 1/2 inch crowfoot wrench/socket with an extension works really well.

Peter Joe

If you use the rubber mount with a stud from each end similar to the muffler mounts you will prevent cracking that is a problem when long studs and rubber washers are used in the interstate tank.

The long stud gives enough leverage to flex the bottom of the tank and it will crack eventually. Jim

I have always used the rubber mounts with a stud on each end, same as the exhaust mounts and head steady, as Comnoz states, prevents cracking, nicely insulated.

John

On early bikes the coil mounting only fixed to one of the frame tabs. This did not brace the frame tabs and the weight of the tank tends to bend the tabs down. (To the extent that a MOT tester managed to break one off while checking my tank for security) I'm of the opinion that the weight of the tank should be taken along the spine of the frame with close cell foam rubber, and the front mounting screws (and rear strap) should only be used to stop the tank moving around or coming off in an accident. Just my thoughts and what I do.

Excellent, thanks for all of this advice. I think my issue might be the foam on the frame under the tank, it's been compressed to the point that it has almost no cushioning at all left in it. The tank it rattling quite a bit even with all four mounting bolts firmly in place so I'll look into replacing all the foam this week.

On my early bike, and early bikes in general, I'm of the opinion that the 'wings' are there just to stabilize the tank. Bulk of the tank weight goes on the main tube. I found Zorries (flip-flops) make a great material for that gasket and also the donuts for the mounting wings. I also added a 3/16" aluminum bracket under the wings because I broke one off and had it welded back on. I also use a jam nut instead of the nylock to secure the tank stud, so there's really no pressure on the wing. The jam nut also holds the reflector bracket nicely and it makes for easy removal with your fingers once the jam nut is loose. I also made an AL bracket for the coils to replace the steel one.