F: Frame Fuel tank rear lugs

[oexing]

Sorry for a somewhat silly question, but I cannot find info about where the rear tank lugs connect to rest of bike. The Argentinian bits of pieces show me nothing about this matter - or do these lugs just stabilize left and right halves of tank by a spacer tube plus rubbers ?
Thanks for any info, pictures never give details in the blackness of that space.

Vic

 

[vibrac]

DO NOT LEAVE OUT THE SPACER ROD AND TUBE or a crack in the tank will arrive
You need T39SS and T38SS and a couple of 1./4" BSF nuts and washers
I use a piece of 1/4 hexagon alloy bar and a couple of small bolts its easier than the standard set up as it can be a real fiddle
tension between the lugs is essential

 

[oexing]

Thanks, so you mean the lugs are not bolted onto the UFM somehow, but just stiffen up the rear halves of the tank ?

Vic

 

[bmetcalf]

Yes, sort of an outrigger support.

 

[litnman]

The 2 bolts FT172/1 that anchor the rear tank lug were drilled for safety wire so as not to over tighten.

 

[fogrider]

To answer your original question, the two lugs do not fasten to the bike itself, it's just a spacer between the lugs to stop the 2 sides of the tank flexing. The spacer lays between the lugs close under the UFM and just ahead of the oil outlet fitting. The gap between the lugs is around 4" , 100mm. It pays to check the spacer is not too short so you don't pull the lugs too much together when tightening the bolt.

 

[LoneStar]

I had to add these to an early B tank, made before cracked tanks flooded the factory's warranty scheme.

One thing to note is that there's a very narrow pathway for the cross-piece T38 to fit, between multiple obstructions. It's best to plan the tab and especially the hole locations with the tank in place. T38 length can be adjusted as needed for a snug fit between the tabs.

 

[oexing]

Yeah, sure I got the lugs on my tanks - but as it is the spacer tube will collide with the valve spring cap. I have 4mm compression plates under the cylinders due to Alpha pistons for lowering c.r. for my age - adds a bit to the problem . Had to deal with one leaking tank already and brazed up the top mounting plate plus tank sealer inside . All my HRD bits will most likely come from different bikes, so I am not surprised about having to deal with all sorts of "adjustments" for finishing two working bikes in the end. So either I mod the tank lugs for repositioning the spacer to clear the cap or I may want to add a lug on the UFM for actually fixing the tank at these places onto the UFM , no spacer then - certainly adding some rubber cushioning as well. So this would ease the life of the top fuel tank mount and the surroundings. Still headscratching about best path to lasting success . . . .

Vic

 

[bmetcalf]

For some long forgotten reason, I use 2 rubbers at the rear of the tank. This made the tube touch the lowest plates of the UFM, so I had to file reliefs in the tube. It causes extra fiddling, especially since my tube is short enough to require a washer to shim the assembly long enough for the width between the tank ears.

 

[oexing]

Bruce, you are quite right: When thinking about that tank support, you better keep in mind to find a way for easy mounting the tank at services. So tonight I had a long look at the design and decided on welding corresponding lugs on the UFM which will have short tube ends with rubber hose inside. So the main weight will go on these and prevent loads on the upper standard tank plate from out-of-center forces on the tank, like from heavy tank bags. Well, not an argument in my case as I will hardly do longer holiday trips - too old for that tiring sports. For that kind of activity there is a 1964 E-Type Coupe´ that just had its TÜV / MOT after sitting 3 years unused in the garage. But then, times are weird these days, CO2 craze, burning cars, Brexit depression in UK, I´d be nervous now having holidays in France, UK and all with the Jag - was a different time only 15 years ago . . .

Vic