Gas Tank Doesn't Fit

I became the owner of the Commando below a few years ago, the picture was taken at that time. It looks like the gas tank fits the way it should (?), but I didn't pay much attention to it before I took it off. It was probably just sitting on the bike as I ended up buying new studs and rubber spacer/washers.

Now I'm almost ready to run the bike again and I can't figure out how the tank ever did fit. The recess in the tank, where the front mounting studs are, is 7" wide and the bracket through which the front mounting studs must pass is 7 1/2" wide. The bracket has to fit inside the recess as the studs aren't long enough to allow the tank to sit above the bracket.

The tank is steel and looks like it is original OEM, not a latter day reproduction.

The only way I can see to get the tank to sit on the frame correctly is to cut 3/8" off the ends of the bracket. I must be missing something?

Cheers! ~ Gary



https://62669905-461974009430622287.preview.editmysite.com/editor/main.php

I have the same tank but there is no bracket for the front , it simply drops down into the 2 big holes. There is a bar type bracket for the rear. 06-3239. Maybe you are trying to make the rear fit the front ?

Yep, there are 2 big holes in a bracket which is integral to the frame (look at the AN parts list for the MK III - there's a photo of the frame & you can clearly see them (for some reason I can't get the page to open) .

Looks like an Interstate tank so it requires the straight , under spine strap (mentioned above, part no. as above from Torontonian) this goes under the frame spine just in front of the seat & holds the rear studs.

I 've a mk III Interstate & find it easier to put the bolt on the left (clutch) side in first (just a couple of threads) ,
then slide the open end of the strap under the spine & onto the bolt from the right side (rubber pad facing the spine),
then line up the tank & strap bolt holes & fiddle & curse the second bolt 'til it goes in(can rest the head on the oil tank if fingers tire
& finally tighten each side appropriately (it's my least favourite job on a Commando).

Don't forget the rubber & steel washers at the front (or some use an exhaust silentbloc I believe), else the vibration will do for you tank.

Others may have different methods!

Mike (MK III)

If the above comments haven't solved your problem, would you post photos?

My '70 has early commando steering yokes which have less offset, so the original roadster tank fit without any problem. When I bought the interstate tank it did not fit, so I cut slots in the front brackets for the gas tank and elongated the bracket by welding a fat washer to it, so I could slide the tank backward which worked. There was no way I could use the original bracket holes without fouling the steering.

Sounds very much as if you are trying to fit the strap to the front? As said above fit the studs to there front holes in the tank then the rubbers. Drop them over the two large holes then I prefer to fit another rubber, the flat washer and the retaining nuts. The back two studs will have dropped either side of the frame, spacer rubbers, strap and nuts. Make sure all cables are out of the way an rubber pads are fitted on the spine.

Oh yes, good point from Peter, make sure that your throttle cables go neatly up into the space twixt frame spine & tank with a clean loop for smooth throttle slide action, failure to do so may result in the cables being 'butterflied' by the tank resulting in heavy throttle action & potential (trouser soiling) & jamming of slides (damhikt!!)

Mike

I measured the distance in the recess of my factory steel Interstate fuel tank and it measures 7 11/16 inches. The front mounting studs between centers measure about 5 5/16 inches. Seeing how your tank recess measures 7 inches I would say that the fuel tank is collapsed a little bit in the saddle area. You would need to somehow spread the tank back out to its proper shape. I hope this is of some help.

Peter Joe

I have often taken a disc grinder to the extreme ends of the front mounts so the tank can seat squarely and have a slight bit of room side to side.

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Ggryder,

There are several different types of Interstate gas tank. And although I cannot be bothered to find and cite a specific thread, I think I've read posts from other forum members on accessnorton.com, that there are manufacturing inconsistencies as well.

Your tank appears to be the later style of tank, slightly narrower than the fiberglass and earlier metal versions which hold substantially more fuel. Some tanks have internal baffling (to prevent fuel slosh?), which I think appeared in the later, metal, slimmer versions of the Interstate tank.


Handlebar choices can affect clearance issues between a stock master cylinder and the tank itself. If sticking with the stock master cylinder, bars with a slightly higher rise may be more suitable.

If the tank has been painted since your posted picture, protect the tank paint during installation and removal by using padding at the front of the tank where it encircles the steering tube of the frame. And because they hold so much fuel, and can be quite heavy, the tank should be drained as much as possible prior to removing.

Due to the weight of a full Interstate tank, other experienced members here have suggested that the solid front studs on Interstate tanks should be replaced with the flexible rubber mounts that are used to mount the exhaust system. This may prevent a leak from occurring as the solid front studs are prone to bending if the tanks shifts.


Interstate tanks are a tight fit, but grinding, hammering, prying, etc. are probably not needed to get it on.


Use bing or google with these parameters to most quickly find other relevant threads on accessnorton.com: "norton commando interstate gas tank site:accessnorton.com"



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This is nothing to do with the rear tank mounting or interference with bars, triple clamps (yolks) or fork legs.

Mike Sullivan described the bracket I'm talking about, "there are 2 big holes in a bracket which is integral to the frame".

The two studs at the front of the tank need to pass through those 2 big holes, far enough to allow a for a large washer and nut to be threaded on underneath the bracket. The space between the bottom of the tank and the top of the bracket is then taken up by a stack of large rubber washers. For that to happen the bracket must be able to fit inside the recess at the front of the tank, but on my bike the bracket is wider than the recess, so the tank won't sit down far enough on the frame.

I was hoping that I might have a wrong frame/tank combination, but it seems like others (Robert_Norton: "Interstate tanks are a tight fit, but grinding, hammering, prying, etc. are probably not needed to get it on.") & ( seattle##gs : "I have often taken a disc grinder to the extreme ends of the front mounts so the tank can seat squarely and have a slight bit of room side to side. ") have had similar problems.

Strange!

Cheers! ~ Gary

Pics please.

Has the tank been pressurised for a leak test or whatever?

Dave

On my Norton,
The front studs on my Interstate tank are 5 1/2" apart
The recess at the front of the tank is 7 1/2" + (The edges aren't completely straight/vertical).
The frame bracket on my bike is 7 1/4" (give or take an 1/8th).

So on your Commando;
The bracket is bigger by 1/4"
The tank recess is smaller by 1/2"
Hence the interference.


The question is why?
If the mounting brackets aren't going to be compromised by trimming them shorter I'd do that.

ggryder said:

This is nothing to do with the rear tank mounting or interference with bars, triple clamps (yolks) or fork legs.

Mike Sullivan described the bracket I'm talking about, "there are 2 big holes in a bracket which is integral to the frame".

The two studs at the front of the tank need to pass through those 2 big holes, far enough to allow a for a large washer and nut to be threaded on underneath the bracket. The space between the bottom of the tank and the top of the bracket is then taken up by a stack of large rubber washers. For that to happen the bracket must be able to fit inside the recess at the front of the tank, but on my bike the bracket is wider than the recess, so the tank won't sit down far enough on the frame.

I was hoping that I might have a wrong frame/tank combination, but it seems like others (Robert_Norton: "Interstate tanks are a tight fit, but grinding, hammering, prying, etc. are probably not needed to get it on.") & ( seattle##gs : "I have often taken a disc grinder to the extreme ends of the front mounts so the tank can seat squarely and have a slight bit of room side to side. ") have had similar problems.

Strange!

Cheers! ~ Gary

Click to expand...

Gary, Sorry that I forgot to say that "the wings" on my frame bracket were also too wide to allow my interstate tank to slide down in to place with the tank mounting rubbers resting on the bracket. I trimmed the wings of the bracket back with a hand held grinder/cut off wheel to make it fit. I did so much more to make the interstate tank fit with my yokes, I forgot that I also had to trim the width of the bracket....

I was curious about this problem so looked at mine.
On the right side there is just a bit of clearance between the 'wing' and tank seam. There is more clearance on the left side.
The tank mount 'wing' is unaltered.
Maybe this photo will help others visualize the potential issue.

Yes that's the kind of pic I've been hoping the OP might share – tbh I'm surprised to hear of this issue, I'd have thought that, once this style of front tank mounting was introduced, there would've been no variation, whatever the style of tank. This on the basis that the same frame could be used to hang whichever style of Commando tank/seat/side panel combo. Evidently not!

Thanks to everyone for their interest. I'm away from home at the moment, but when I get back in a few days I'll post some pictures. Bob Z's picture, above, illustrates the problem quite well though.

It looks like this is, "a thing" and could be just wildly generous tolerances on Norton's part, in which case I'll feel (a bit) less concern about cutting bits off a nice, original frame.

One other thing may point to tolerances: the only reason I can see for the (large) size of the holes in the bracket (or wings), through which the front mounting studs pass, is that they allow for a lot of variation in the location of those studs.

Regards ~ Gary

Gary I share your concern about 'cutting bits off a nice, original frame' – but opinion seems to be piling up in favour of doing that if need be. Really, I'm surprised, but there it is.

About the large size of the holes in the bracket, I've always thought this is sensible, in that it allows for variation. In my case, when installing the tank it needs to be lowered onto the frame and then slid forward a little so the top yoke (not 'yolk', people! sorry ... ) doesn't scratch the paint. I don't know if that's normal, but the large holes mean it's really easy for me to locate the studs in the holes, and I have some wiggle room to position the tank so the nose of the saddle meets the back of the tank just how I like it. Off the top of my head though, I would think the sandwich of large rubber washers tends to 'fix' the location of the tank via those large holes, once the nuts are tightened on the studs. So the front of the tank is rubber-mounted, but secure. On the other hand I like the idea of using exhaust mounting rubbers there, that's a new one to me ...

"On the other hand I like the idea of using exhaust mounting rubbers there, that's a new one to me" ... exhaust mounts work well on my bike ,i have a roadster tank