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By Wheaters
#90967
A few days ago I was out riding the bike when I heard a tinny rattling noise. I assumed it was the regular issue of the top of the exhaust coming loose again. Strangely though, that problem is usually accompanied by popping in the exhaust and that didn't happen.

On getting home I checked the bike over and revved it. The rattle was coming from behind the engine and at first I assumed it was the head steady bolt come loose but on checking that saw it wasn't. Both rear tank brackets had broken free from the tank itself!

I took the tank off (it was only held on by the front bolt). The welds on the brackets had fractured; the factory had only tacked them on in three or four places. I had repaired one some some time ago. There was no penetration on the welds on the non repaired one, only four blobs "glued" on, inside the tunnel.

I drained the tank, took off the fuel tap and left it upside down for a couple of days in the warm sun to vent. I then gave it some extra heat from my heat gun to ensure it was clean inside. I then swilled it round with hot soapy water and drained it again and dried it out a second time. When I was happy it was safe to work on I ground off the old welds and paint and cleaned up the brackets for re-use. Unfortunately I then got called away from the job; SWMBO needed assistance on a "little project" that turned into a marathon taking the whole day - enough said.

On returning to the tank I tack welded on the first bracket, tried the tank on the bike for fit (perfect) removed it and welded it on for good. I then used it as a guide to fix on the second bracket. All was good so I did a leak check, using hot soapy water. All good! Those welds weren't going to come off!

I painted the damaged area. Etch primer, colour coat, petrol proof laquer. A good job all round. Until I tried to fit the tank on the bike....

I'm not sure what happened but somehow the brackets were just far enough out so the rear bolt would not go in. :shock: :oops: I think the tack welds were good, but the "proper" welding had caused some distortion. A case of rushing the job and distraction. I should have known better.

Needless to say, getting the brackets off a second time destroyed them - my welding was a lot better than the original. I needed new brackets.

I took a drive to my local Wickes where they stock assorted strips of steel in metre lengths. Queued to get in. none of the required size in stock. Queued to get out - social distancing etc! Best part of an hour wasted.

Went home, rooted around all the old tins and boxes of junk in the garage and eventually found an old bracket that could be cut in half and cleaned up and drilled to make two brackets. Fiddly job but eventually ended up with two brackets!

This time I made a jig from a piece of 4x2 timber using my pillar drill (should have done this the first time). Drilled it to match the frame fixings, making absolutely sure everything was "square". Bolted it inside the tunnel of the tank, bolted both new brackets to it and marked them up for welding. It was then I realised that the underside of the tank isn't true, the tunnel has a marked twist in it! My identical brackets didn't fit in the same positions inside the tank tunnel, one has to go further in the tunnel than the other. The tank was no doubt hand built and the tunnel wasn't lined up parallel to the sides of the tank. This partly explains my error in welding them on out of line - Doh!

So, having checked, rechecked and checked again, I tacked on the first bracket. Then I fitted and refitted the tank a number of times until I was sure both new brackets fitted correctly. Perfect. Welded them on securely . Still perfect!

Just final leak check then I can paint it again. BOTHER! Now there's a serious leak, apparently coming from behind one bracket :evil: . Cup of tea time.... with a lot of swear words between each sip.

Anyway, thankfully "only" a cracked seam weld next to one edge of a bracket. More welding. Leak check now OK.

Tank now awaiting paint to harden before refitting. Fingers crossed.... :roll:
By singleminded
#90997
The rear mounts on my Bullet tank have both fractured at the weld. The rear mount is the worst piece of engineering I have ever seen. The front of the tank is mounted in a flexible rubber bush (absorbs vibration but obviously allows a little movement) - big tick for this one.

The rear mounts are solidly attached to the frame by a bolt which also secures the head steady..... I'm surprised they haven't all failed.

I bought some thick neoprene sheet and cut it to fit over the top frame tube. The tank squeezes down ever so snugly on that and then the front mount is fitted. No vibes through the tank, no irritating broken rear mounts, no need to curse the genius who thought a solid mount at the back and a flexible one at the front was a good idea.
User avatar
By Wheaters
#90999
Even more of a saga this afternoon. I smelled petrol while the bike was parked up for my lunch stop in the Peak District. The seam near one of my newly welded rear brackets has cracked.

To round off the day the bike suffered a rear puncture just outside Monyash. The B road into the village had been resurfaced with limestone chippings and they’d put down enough to surface The M1; I’ve never seen such a thick laye, all loose and no fun to ride on. I felt the back end step out and turned back to the village green. I was given some assistance from a Moto Guzzi rider who had an electric tyre pump. The tyre held some pressure for a while but I then had to stop every three miles or so to pump it up again, by hand. I pulled in at Baslow and took off the back wheel and fitted a spare tube I had in my pack. I rang my wife to tell her I might need assistance, only to have my phone battery fail during our conversation. I managed to “borrow” a phone call from a kind lady passing by (speaker phone, social distancing observed)! Unfortunately the second tube gave out about ten miles from home. I managed to limp the bike to a petrol station and the proprietor kindly offered to charge my phone. I rang my wife who came out with our van and we put the bike in the back and strapped it down. We got home about 8pm.

I’m now sitting by the bike, draining the petrol tank again and also draining a bottle of cider for me.

New tube and tyre needed. I might also have to replace the tank.
Yes, these solid rear tank mounts are not a good design!
By PeteF
#91000
I just cut the brackets off before they cracked and made up a rubber piece to wedge the tank onto the grame. Never moved again. My new euro 4 has proper tank mounts 😁
By Daiwiskers
#91001
That lot just sucks

Tomorrow can't be worse

Well hope not Dai
User avatar
By stinkwheel
#91003
My understanding was that the tank on a bullet is a structural frame member. So not bolting down one end impairs the structural integrity of the motorcycle.

I could be wrong though because I can't remember where I heard that.
By PeteF
#91004
Don't think so SW, those tabs are not strong enough to give any structural strength.
By Beezabryan
#91005
Sorry Stinky but your understanding is confucious, it is the engine which is the stressed frame member. The fuel tank is merely a metal container attached to the top frame tube and headstock.
By PeteF
#91006
There are bikes that use the tank as a stressed member. Tiger cub springs to mind. We used to fit a steel brace when fitting an alloy tank for trials use.

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