Author Topic: Petrol tank  (Read 388 times)

Online Rex

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Petrol tank
« on: 03.04. 2019 09:37 »
Between 50-55mph on my 1951 A7 the petrol tank noisily vibrates to the extent that when I first heard it I thought something bad was happening. It seems to be caused by the clearance between the through studs and the frame mounting holes allowing 1-2mm "play" at the mounts. The frame holes aren't worn.
The studs are the correct 5/16 and 3/8 BSCY so is there a cure I'm missing, short of turning up some slightly over-size studs?

Offline muskrat

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Re: Petrol tank
« Reply #1 on: 03.04. 2019 11:12 »
G'day Rex.
Mine does too. The front stud goes through a rubberized bush. I just used a piece of fuel hose. Helped a little. The rear is solid mount so I used rubber grommets into the tank slotted mount that was a squeeze onto the stud. It's now reasonably quiet till we hit 70mph.
Cheers
'51 A7 plunger, '57 A7SS now A10CR, '76 XT500, '77 AG175 '83 CB1100F, '81 CB900F project.
Australia
Muskys Plunger A7

Online Rex

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Re: Petrol tank
« Reply #2 on: 03.04. 2019 11:34 »
Musky, this tank has a solid front mount too. Just a stud through the frame... *conf*

Online Greybeard

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Re: Petrol tank
« Reply #3 on: 03.04. 2019 12:06 »
My bike, from 1955, has rubber bushes in the headstock at the front and in the tank lugs at the back.

Rex, do you have the stiffening plate fitted beneath the tank?

Offline cyclobutch

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Re: Petrol tank
« Reply #4 on: 03.04. 2019 12:08 »
As my mother once told me - you just need to keep your knees pressed more firmly together.
Various, including ...
'58 Iron Head Flash Bitza


Online Rex

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Re: Petrol tank
« Reply #5 on: 03.04. 2019 12:37 »
My bike, from 1955, has rubber bushes in the headstock at the front and in the tank lugs at the back.

Rex, do you have the stiffening plate fitted beneath the tank?

Yes it does have it fitted, I suspect BSA changed to your type as the earlier type did just what mine still does and rattled!
Gripping the sides of the tank with my knees helps, but it's s till audible.

Offline Swarfcut

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Re: Petrol tank
« Reply #6 on: 03.04. 2019 14:49 »
Rex  If you have the early non rubber front tank frame mounting, a  penny washer each side sandwiched between the tank front mounts and the frame will allow the tank mounting lugs to be tightened against the frame, without putting any strain on the tank. This will also stop the through stud rattling in the frame once everything is tightened.
 Swarfy.

Online Rex

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Re: Petrol tank
« Reply #7 on: 03.04. 2019 17:47 »
Done that mate. A nice large rubber penny washer lightly compressed on each side....still vibrates though. *sad2*

Offline berger

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Re: Petrol tank
« Reply #8 on: 03.04. 2019 18:55 »
chuck some carpet underlay round frame tube.

Offline Swarfcut

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Re: Petrol tank
« Reply #9 on: 03.04. 2019 19:06 »
Rex,   Last chance saloon for the tank mount. Try the old beer can sheet metal wraparound on the stud to take up any rattle, and use metal penny washers. Plus berg's  carpet trick.

 Ian Drury....sadly missed, him of the clever b*s*a*d*s  song from 1979, as in your earlier post today.

 Swarfy.

Online Rex

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Re: Petrol tank
« Reply #10 on: 03.04. 2019 21:09 »
Beer in cans? Heresy! I do have some shim stock though so could be worth a try.

Online Rex

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Re: Petrol tank
« Reply #11 on: 16.05. 2019 09:22 »
Just a quick follow-up to this. The problem I have is a later rubber mount-style tank on an earlier non-rubber mounted frame, allowing the mounting studs to vibrate in the frame cross drillings.
The clearance was too small for shims etc, so I built up the diameter of the stud with weld in the area where it would contact the frame and then turned it down on the lathe to a light push fit.
It's gone from a 2-3mm rock of the tank to no movement at all. Well pleased with the result.

Offline Minto

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Re: Petrol tank
« Reply #12 on: 18.05. 2019 19:58 »
Jobs a good 'un!
52 A10 plunger