Petrol tank removal

[JulianS]

There needs to be a larger diameter plain washer between the nut and the rubber so that the rubber expands in diameter and gripsmthe tank when nut tightened.

[Phil C]

There is the one on the second photo, what I call a penny washer, almost as big in diameter as the rubber.  That's okay, isn't it? But the rubber bit isn't the standard rubber bit, is it? It seems to have a hole in the middle which closes up when there's nothing filling it.  Phil (novice)

[AWJDThumper]

It's good news that you've got the right brackets - it's difficult to know why he used all that foam rubber?

The tank is held in position by the shaped rubber bung (40-8085) inside the tube down the middle of the tank. The idea is that this is compressed by tightening up the nut so that it expands outwards to tightly grip the tank tube . There should be two spacers on the centre bolt. The lower one with a washer between it and the rubber bung is there to give the correct height for the bung inside the tank tube. The other spacer then goes inside the bung and is slightly shorter than the thickness of the bung. When you do the nut up it should tighten up against the two spacers and the two washers above and below the bung to allow it to be adequately compressed. Unfortunately, since the assembly rarely survives in its original form, it always seems to be necessary in my experience to rejig it so that it works correctly.

[Phil C]

I don' think mine is anything like the arrangement you describe - as you'll see for the photos.   Phil (novice)

[AWJDThumper]

Is it possible to take a picture showing all the separate bits you have including the bolt so that we can see what you might be missing? If you place a ruler alongside the bits, we can then see whether you've got the correct length of the bolt and spacer(s). 

[AWJDThumper]

Here's a picture of the set up for the tank on the C15 I am restoring which should be identical to your B40. The bung is an old one and will be replaced and the longer spacer needs to be reduced by 5-10mm in length to fit the bolt (and the washers aren't the correct ones). As you can see, the shorter spacer is much shorter than the depth of the bung which allows it to be compressed by the nut.

[Phil C]

Here is the set-up on mine. The rubber was a stiff push fit into the hole (straight hole through tank) and appears to be a rough cut home-made job? I can see that with the orthodox set up the top nut tightens, and squeezes out the rubber, until the nut hits against the top spacer. But with mine it appears to be just tightening onto the rubber?  Anyway, any thoughts on what I've got please?  I'm thinking maybe I need to get it as per AWJDT's.
Phil (novice)

PS AWJDThumper's photo is much clearer than my fuzzy one - any idea why? Is mine simply short of pixels?

[AWJDThumper]

All the bits are available from Burton Bike Bits which is where mine recently came from. Only problem was the larger spacer is too large and will need to be trimmed down to the correct length.

[Phil C]

Thanks. What is the correct length?

[JulianS]

Phil you have the wrong rubber.

[Phil C]

Yes, I think it must be something a previous owner made. I'm going to try to get a proper one.

[AWJDThumper]

You can see from my pic that the two spacers are about 1" and 2" long. The shorter one is fine but, for everything to properly fit on to the bolt, I will need to shorten the longer one by slightly more than 1/4" - this is despite buying all the correct bits from BBB. Your long spacer might be ok but I can't really tell from your pic if you don't have the correct bolt as in my pic. If not, I would buy the correct one from BBB.

[Phil C]

Thanks very much.

[Phil C]

AWJDT's photo of parts, and the explanation of how the arrangement works, seem very clear. But the drawing kindly shown by AWJDT shows a rubber sleeve(41-8020). What is that for?  Also, I notice there are more washers on the drawing than on the photo?  As always, any advice is much appreciated.  Phil (novice)

PS Will spring ever arrive?

[AWJDThumper]

I think the parts drawing is a bit confusing. If your tank has a simple tube down the middle then the arrangement shown in my pic and Julian's earlier drawing are correct. However, some tanks had a small cup in the top of the tank tube and a tubular bung was designed to fit in this cup and was pulled down by the nut on the end of the fixing bolt - it wasn't designed to expand like the shaped bung in my pic. The parts book picture appears to show both means of fixing the tank.