Oil Tank Rubber Mounts

Has anyone run into self destructing oil tank rubber mounts? I replaced mine and within 150 miles the rear one sheared in two, leaving my oil tank flopping in the breeze. Should I be looking for another problem somewhere or just chalk it up to a bad piece?

Thanks,
Geoff

Seems obvious there is some sort of excess vibration issue or the mount itself is poor quality (anything is possible parts-wise nowadays). Is your bottom rubber mount present and in decent shape? They get brittle, turning to hard plastic after a while and that might cause excessive movement at the other mounts.

Strange. Maybe new pattern parts are not up to snuff. The originals on my MKIII were fine after 35 years but I put new ones in during the rebuild so I hope the new ones don't self destruct like yours.

I think getting these mounts with fresh rubber is unrealistic. Possible, but unrealistic. And if you do, how well have they been bonded/vulcanized or what ever they do. I gave up on those mounts some time ago. I use a bolt to span the distance and a piece of automotive fuel hose over the bolt and between the mounting points, squeeze it up to plumb. Stainless bolt and locking nut. 1/4 20, no big whoop, AOK!

Although not OEM (oh my goodness gracious), it's my bike, I do what I want!

Thanks guys. I'll check the bottom (never looked at it) and do the fuel line fix.

"I use a bolt to span the distance and a piece of automotive fuel hose over the bolt and between the mounting points, squeeze it up to plumb. Stainless bolt and locking nut. 1/4 20, no big whoop, AOK!"

I went through something similar on some air conditioner compressor mounts on a boat. I tried that method (bolt/hose) but the vibration/noise transmitted from the compressor to the boat was greater than with the shock mounts which look exactly like larger versions of the Norton's oil tank mounts. So I installed new mounts. Maybe it's not really an issue but I'd be concerned that the metal tabbing to the tank might fracture over time.

There's been a bit of discussion about oil tank mounts.

I'm going with:

Use the headsteady rubber mounts as they are a bit more substantial.

Also no bolt in the bottom of the tank.




You do have to hog the holes out a bit.

Dave - This is similar to what CNW supplies with their remanufactured oil tanks. The rubber isolating buffers are not quite as huge as the muffler mounts though. They said you may have to redrill the forward mounting hole in the frame which I did have to do but the old hole is covered by the new buffer. They also supply a rubber pad for the bottom and a thinner rubber pad for the back of the battery box. The bottom bolt hole is completely done away with and a flat plate is welded in. Once mounted up it is very robust.

Normally I try to stay away from what I think are unnecessary mods but this one is worthwhile. It is not a question of the new rubber being not as good. It didn't work even when the bike was brand new. Either the rubber separates or the rear tab breaks.

batrider said:

Dave - This is similar to what CNW supplies with their remanufactured oil tanks. The rubber isolating bushings are not quite as huge as the muffler mounts though. They said you may have to redrill the forward mounting hole in the frame which I did have to do but the old hole is covered by the new bush. They also supply a rubber pad for the bottom and a thinner rubber pad for the back of the battery box. The bottom bolt hole is completely done away with and a flat plate is welded in. Once mounted up it is very robust.

Normally I try to stay away from what I think are unnecessary mods but this one is worthwhile. It is not a question of the new rubber being not as good. It didn't work even when the bike was brand new. Either the rubber separates or the rear tab breaks.

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As you can see that if I don't adjust the rear tab I will have problems. I'll also shorted the stud slightly.

I've heard that someone even used Velcro® to further secure the oil tank, which would also provide a little cushioning.

I've sewn some industrial velcro into my battery strap. It's a lot stronger than the velcro that you normally think of on shoes and such...and it's cheap

Now I've never had trouble with the mounts but they have to be assembled with no stress on them. My problem like 'Batrider' says is the rear tab fractures. I lost count of the repairs I've done (wider tabs, thicker etc) so a few years ago I braced the rear to the filler tower with a piece of welded strip. It's crude but transfers the fore/aft shaking into the tower instead of cyclically bending the tab. 10,000 on it's still intact and I used to only go 2-3000 before it broke. Needless to say the lower mount should be in good nick and mine is beefed up with a plate around the boss. Strangest thing though is when I did this on an old Ebay buy that tank had never had a rear tab repair and it looked like it had seen some service. Why do some survive OK? This is what I did and it's neater than it looks!!

I love this site! Thanks for all of the replies - my Commando is down now until I can scrape together more parts (like a horn) & I can fix the oil tank with beefier rubber mounts as it seems the oil tank has survived so far...

Again - the responses I have been getting to my freshman questions has been really outstanding - thanks to everybody. Soon I'll have the gumbtion to start assembling my '73!

Geoff

geoff71 said:

I love this site! Thanks for all of the replies - my Commando is down now until I can scrape together more parts (like a horn) & I can fix the oil tank with beefier rubber mounts as it seems the oil tank has survived so far...

Again - the responses I have been getting to my freshman questions has been really outstanding - thanks to everybody. Soon I'll have the gumbtion to start assembling my '73!

Geoff

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Take care, because there's more to this than meets the eye. Beefing up the rubber mounts may just move the problem to the next weakest point. The rear bracket fractures for a pastime and repeated repairs and / or beefing up the bracket can cause the tank itself to crack. Potentially more serious is the bottom mount, which concentrates the weight of the tank and its contents onto a small "bobbin" welded into the base of the tank. Add in vibration and the movement allowed by the top rubbers and over time, the base of the tank cracks around the bobbin with the potential of dumping oil onto the rear tyre. On my bike, the first sign of this was engine oil dripping off the very back of the swinging arm when the bike was parked up in the garage (oil tank onto battery tray, down the mudguard onto the top of the swinging arm, along the bottom of the swingarm to the back end, then onto the garage floor....).

I picked up a seemingly good-condition tank at an autojumble, but the rear bracket has failed after only 200 miles and this one leaks around the bottom mount as well! Grrrr!

I like the sound of CNW's modified oil tank. Anyone know of something similar available in the UK?

Mitch

I use Harley shovel head oil tank rubber mounts. They are larger than the Norton tank mounts but smaller than the muffler mounts and have 1/4-20 studs.

http://cgi.ebay.com/ebaymotors/5-PA...0003119QQptZMotorcyclesQ5fPartsQ5fAccessories

I have never had an issue with the bottom peg breaking, but have had the rear tab fracture on several. Using the larger mounts on both the front and rear of the tank seems to help. I also am careful that the mount tabs are not stressed when installed. Usually bending the front tab slightly can align it properly. With the H-D mounts and careful alignment I have never had to fix an oil tank tab more than once.

I used the CNW oil tank mod on my '73 Roadster 750 restoration. Well thought out, works great and should last for a long time. I plan on doing the same mod on my current '74 850 project.
Good luck!
Tim

I like the sound of CNW's modified oil tank. Anyone know of something similar available in the UK?

I took the first failure to a radiator repair shop, they welded a square plate with a hole in the center to allow the bobbin to poke though, they also welded around the bobbin, this has worked fine and I have had the same done to the next failure on another bike too.

RonL,
thanks for the ebay link for the rubber mounts. I just picked up a 5 pack for $8.99 and free shipping.
I'll swap mine out as a preventive measure. My rear tab looks to have been rewelded and a very nice job
by an unknown source while in possession of the previous owner.
I replaced both upper mounts w/ Andover Norton pieces from Old Britts.
They have held up nicely so far 1400 miles later.
I did replace the rubber spacer/bushing also on the bottom mount which the affixing bolt runs through.
It's like a miny Isolastic mount only no shims. I wonder how many out there are missing the inner
collar reinforcer that the bolt passes through?
My tank has survived so far. I do have a spare on standby that maybe will go to CNW for a modification.
Marshal

I use Harley shovel head oil tank rubber mounts. They are larger than the Norton tank mounts but smaller than the muffler mounts and have 1/4-20 studs.

Click to expand...

That's what I did, too. Much stronger and work great.

slupdawg,
did the Harley oil tank mounts bolt right up or did you have to open up the frame mounting hole or any other mods need noting? Did you leave the bottom mount in tact.
Thanks,
Marshal

MarshalNorton said:

slupdawg,
did the Harley oil tank mounts bolt right up or did you have to open up the frame mounting hole or any other mods need noting? Did you leave the bottom mount in tact.
Thanks,
Marshal

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someone said they were 1/4" like the stock Norton ones. The headsteady ones are 5/16".