Oil Tank Fracture

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Oct 17, 2007
Howdy from New Zealand.

Its high summer and my 73 850 Roadster is getting lots of use.

I have put a new oil tank on 1500 miles ago and the back strap/support has broken off.

I understand the good fix is to weld a stronger bracket on.

Has anyone had to fix this problem?

I have welded up the oiler pipe,any other mods to the tank while it is out?

Baldrick said:
any other mods to the tank while it is out?

Strengthening the lower tank mounting is normally a good idea if that has not been done already?
Have done a couple and if your bike breaks brackets like mine even with unstressed rubbers the heavier bracket will go eventually. I first widened mine to 1.25" in 060" steel and that lasted 8000 miles. Just put a replacement tank on last year with it's original bracket and it went 600 miles. Must have done a few thousand on another bike but it didn't like my vibes!
What I did was to weld a brace to the filler tower to stop the bracket flexing at the weld.
The base reinforcement is a must while it's out and beefing up the rubbers with some 5/16" HD Panhead oiltank mount is supposed to be a cure for stock mount failures which I don't seem to get.
Loosening up the clearance in your isos a bit will decrease the vibration frequency and thereby prevent oil tank bracket failure. This has worked for me, anyway.
fractured oil tank mount

I too have recently found the rear oil tank mount on my 74 to be fractured. It occurred to me that perhaps it is held too rigidly by the stock three point mounts and that just maybe I'd be better off leaving it that way. Has anyone else ever put a significant amount of miles on a bike with such a broken mount ? I am wondering if the extra sloppyness would relieve the stress on the other mounts, OR, cause the remaining mounts to fracture sooner ?
your comments appreciated,
Hi All,
Thanks for your responses.

I will put a heavier guage bracket on to strengthen the original.

A new Dave Taylor head steady is in the mail from RGM and when I fit this i will reset the isolastics.

When you are mentioning strengthening the base I am unsure of what you mean.

The bottom of the tank is held onto the frame by a very hard to get nut and rubber mount which is my wife Di's job to tighten!

Please explain more?

Cheers Baldrick

i believe the tank can over time split somewhere around the bottom bolt. I have seen some suggest leaving that bolt out so just a two point fixing.
When my tank was last out, to fix the broken top rear bracket of course, i had a doubler plate welded around the bottom bolt fixing location as well.

A yellow roadster by any chance??
I beefed up the bottom mount on mine by cleaning up the area and brazing (not welding) a washer that fitted over the mountilg bolt. This made the area round the bolt stronger as it is prone to cracking just there

have to admit to doing my "welding" with a cheque book, so could well be braised in my case as well.
Another cheapskate way is to epoxy (Araldite metal) a piece of 1/8"sheet steel or aluminum in place about 2.5 x 1.5", making sure lots of epoxy is applied and squeezes thru the hole you make for the mount so its fully supported. That way the mount is supported over a large area and not just in the brazed or welded areas. I did it on two tanks cos I had no oxy gear. One tank has 18000 miles on it now and no signs of cracking. Just the rear brkt that's an issue with me and I have the ISO's at max with squared ISO tubes etc, etc. Been through it all on eliminating high speed vibes and it's probably acceptable now.
All rebuilt and on the road

Howdy All,

I have got the bike back on the road with the oil tank strengthened and Dave Taylor head steady fitted.

I think the reason that the tank cracked was the front isolatsic was done up very tight.

The bike is now running smoother and truer than ever.

Of on a NOC club ride next month for a few days up the coast in Colville and hope everything stays together.

Could you tell me what you think of the Taylor head steady as far as vibration and handling are concerned?
Hi Larry,

I am very impressed with the head steady.I got it from RGM and it was item 664B with the spring device.

I have ridden the bike around a road circuit that has an off camber left hand corner that has had he crapping myself in the gravel more than once and I now just sail thru it trouble free.

The bike has changed and I am feeling little or no vibration when ridding 60-70 mph.

The instruction manual suggests I will get vibration at high speed.
I haven't noticed as I am usually watching out for traffic police.

I am off on a tour two up next weekend and will be interested how it feels after 4 hours of riding.

oi tank

Another method I use to prevent the tank bracket from breaking is to eliminate the bottom bolt and fabricate a"pin" in place of the bolt. This pin will then locate in the grommet. You can also use a soft rubber pad glued to the position under the tank to help isolate the vibes, let the tank rest on the pad. Grainger sells these vibration isolation mounting pads in various sizes. You can cut to size.
Also, I have fabricated a rubber "collar" that I place around the filler neck under the cap. This will keep the tank from rattling around and banging into the frame sections. With this, you can elininate the rear mount entirely. I've been using this now for at least maybe 10 years and no problems with the tank. This may not "look" cool but then no one can see the mod when the seat is in place.
Just thought I would share this with anyone who may want to save a few bucks on welding a new tab and then having it just break again.

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