Petrol tank nuts

Don Madden · Post by **Don Madden** » Fri Jun 22, 2012 2:51 am

Your spanner is likely 5/16W-3/8BS which fits 3/8in BSC & 3/8in BSF as well. The old Whitworth bolts had larger heads. The only Whitworth fastners on most AMC bikes are for Burman gearboxes. The rest are BSC or BSF with a couple of exceptions as 1/4in into soft metals. Cheers, Don.

itma · Post by **itma** » Fri Jun 22, 2012 10:31 am

someone has modified your tank then?

bigwol · Post by **bigwol** » Fri Jun 22, 2012 11:12 am

Can you post photos of it Ray?

alanengineer · Post by **alanengineer** » Fri Jun 22, 2012 11:48 am

I have a modified tank where someone has puched the wrong bolt up through the bottom of the tank and welded studs in. And, i have seen many more. Seems a standard bodge to me

greasemonkey62 · Post by **greasemonkey62** » Fri Jun 22, 2012 3:52 pm

I dont think the tank has been modified I think the fitting is the same as I had on my nineteen sixty something AJS model 8 lightweight years ago, the bolt which does not have a head for a spanner but a circular plate with a tongue that fits through a slit in the rubber bung (one and a half inches high and one and one eigth wide) that the bolt goes through, these fit into circular recesses in either side of the front base of the tank, the bolts threaded ends then pass down through lugs on the frame, when tightened up from below the lugs the rubber is compressed and expands in the tank recess and works like a rawlplug and is also a vibration killer, very ingenious, but it only works if you are not short of one of the nuts, now I have it out of the tank recess it is 3/8 ths bolt diameter and 20 tpi , cant get the hang of putting pics on here so I will post on new pics instead.

bigwol · Post by **bigwol** » Fri Jun 22, 2012 5:15 pm

Got you now, later type tank with recesses in the front of the tank and a rubber band at the back. Sorry cant help with thread but hazard a guess is bsf.

greasemonkey62 · Post by **greasemonkey62** » Fri Jun 22, 2012 9:37 pm

got it now it is a 3/8 ths BSF , thanks all, the nuts (when I had two, one came loose under vibration) are/were with a locking insert like the nylock but they have become worn with use and the locking insert bit became worn so they were just as ordinary nuts, were nylock type nuts available in 1962 when the bike was new? they looked old and I thought they were original.

Malleon · Post by **Malleon** » Sat Jun 23, 2012 12:17 am

Simmons (?) nuts, early versions, had an insert similar to a red fibre washer as I remember, and I'm sure they were in use by 1962.
But as usual, my memory ain't wot it used terbe.

Duncan · Post by **Duncan** » Sat Jun 23, 2012 12:41 am

Ray, I think it is the centre web cap stud nut that you want, 016846, this has a small extension that has a cut each side to lock on to the thread.

Don Madden · Post by **Don Madden** » Sat Jun 23, 2012 3:12 am

Center cap nut is 3/8in but BSC, not BSF. Cheers, Don.