Roadster fuel tank packing

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olympus

olympus

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Hi all
With regard to roadster fuel tank mounting i have a few of questions
  1. AN sell a Roadster fuel tank mounting kit, but this uses studs & rubber washers for the for mountings
  2. Did i not read that its best to change these to exhaust bobbin style metalastic mountings??
  3. Are these direct replacement without modification?
  4. With regard the rubber packing under the tank and on the spine of the frame, does anyone have a photo of the positioning/size/thickness of such packing please.
Thank you
 
olympus said:
  • Did i not read that its best to change these to exhaust bobbin style metalastic mountings??
  • Are these direct replacement without modification?
Click to expand...
Yes as the thread is the same (5/16" UNF).


The 850 Mk3 had them at the rear as standard although you might want to fit a little extra packing if used at the front?.
https://andover-norton.co.uk/en/shop-drawing/151/fuel-tanks-and-fittings#

olympus said:
With regard the rubber packing under the tank and on the spine of the frame, does anyone have a photo of the positioning/size/thickness of such packing please.
Click to expand...

'Thick' 06.2567 at the rear (below). 'Thin' 02.6359 at the front (no photo).

Roadster fuel tank packing
 
Hi

Just been through this exercise and found the following:

The exhaust bobbins (mounts) fit. You may need to pack out gaps between them and the tank if the surfaces are not perfectly parallel.

The AN studs and rubber washers should be fine for a Roadster tank unless it is old and rusty with thinner metal on the bottom.

The Interstate tank with extra weight needs better support. This should certainly have the bobbins and an upgrade is recommended.

I found the variations in top isolastics. cabling, tank base etc etc meant there was no hard and fast rules around rubber positions and thickness. I experimented until I was sure I had clearance and a good fit.
 
Last edited:
I believe the idea is the metal plate on the bobbin pulls down against the tank bottom and spreads the load rather than the stud which can lever back and forth and eventually crack around the hole.

The rubber would take a lot to shear and you can monitor them for decay.

Generally I would see these as a consumable item to be replaced every 10 years or so.
 
Last edited:
Timely post as I am sorting out a 74 Mk 2 right now.
I have had several Commandos including a brand new one 73 and can't remember how the original was.
Parts manuel and Andover show 5 bobbins on the front and 4 on the rear.
4 bobbins are roughly equal to one muffler mount.
I usually put 4 bobbins on the front then mount the tank then another bobbin then the washer then the nut.
Making a bobbin sandwich at the front.

Not sure this is correct. Any one know if they orginally had 5 bobbins on top?

Intereseting note on the 71,72, Mark 3 show 4 bobbins on the front.
 
MichaelB said:
Timely post as I am sorting out a 74 Mk 2 right now.
I have had several Commandos including a brand new one 73 and can't remember how the original was.
Parts manuel and Andover show 5 bobbins on the front and 4 on the rear.
4 bobbins are roughly equal to one muffler mount.
I usually put 4 bobbins on the front then mount the tank then another bobbin then the washer then the nut.
Making a bobbin sandwich at the front.

Not sure this is correct. Any one know if they orginally had 5 bobbins on top?

Intereseting note on the 71,72, Mark 3 show 4 bobbins on the front.
Click to expand...


To clarify the nomenclature. You are talking about rubber washers not bobbins. An exhaust bobbin (mount) is a mounting piece with two steel washers and studs bonded to a rubber spacer. ie just like what hold on your exhaust on a standard Commando.

These can also be used to mount the tank. But just one per corner.
 
I used 3/8" closed cell Neoprene as a spine backing. The tank slides over it and snugs into position wherever I place it, no twisting or sliding on the frame.
Eliminates any clanging or banging with the snug fit and allows the tank studs to pass through the front frame mount holes without any squirming or wandering.

I can really dial in the exact height I want the tank to ride on the frame simply by layering the neoprene running underneath the length of the tank.
The rear strap is mounted on the back tank studs and held in place with nylock nuts which are also adjustable in height via fender washers with rubber washers backing them. Don't really need the rear strap as the tank sits firmly and securely on the neoprene but securing it down makes me feel better.

I got the neoprene on ebay. Bought a used wet suit top for $11.00 and just cut it my sizing needs.

Roadster fuel tank packing
 
Lineslinger said:
I used 3/8" closed cell Neoprene as a spine backing. The tank slides over it and snugs into position wherever I place it, no twisting or sliding on the frame.
Eliminates any clanging or banging with the snug fit and allows the tank studs to pass through the front frame mount holes without any squirming or wandering.

I can really dial in the exact height I want the tank to ride on the frame simply by layering the neoprene running underneath the length of the tank.
The rear strap is mounted on the back tank studs and held in place with nylock nuts which are also adjustable in height via fender washers with rubber washers backing them. Don't really need the rear strap as the tank sits firmly and securely on the neoprene but securing it down makes me feel better.

I got the neoprene on ebay. Bought a used wet suit top for $11.00 and just cut it my sizing needs.

View attachment 10442
Click to expand...


I like the tidy fittings on your bike. The carb tops, the coil mount, the oil line mounts etc.

Nice tidy job !!!!
 
Lineslinger said:
I used 3/8" closed cell Neoprene as a spine backing. The tank slides over it and snugs into position wherever I place it, no twisting or sliding on the frame.
Eliminates any clanging or banging with the snug fit and allows the tank studs to pass through the front frame mount holes without any squirming or wandering.

I can really dial in the exact height I want the tank to ride on the frame simply by layering the neoprene running underneath the length of the tank.
The rear strap is mounted on the back tank studs and held in place with nylock nuts which are also adjustable in height via fender washers with rubber washers backing them. Don't really need the rear strap as the tank sits firmly and securely on the neoprene but securing it down makes me feel better.

I got the neoprene on ebay. Bought a used wet suit top for $11.00 and just cut it my sizing needs.

View attachment 10442
Click to expand...

Can i ask regarding headlamp shell cable routing, your goes down to the bottom of the steering head stock, then up between the two frame tubes.. is this original factory routing??

Thanks
 
Thanks for this Les ... as i would have routed the loom to the left of the head stock not to the right
 
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