How is my 74 Interstate metal fuel tank supposed to be held down?
referring to the AN tank pictures I’m not too certain which one is mine. If it is the one I believe then it is shown having studs front and rear with many rubber mounts. Mine came with 2 studs at the front and 2 bolts at the rear and a steel strap with an oblong rubber mount, it also has a slot at one bolt end.
should I therefore retain the 2 bolts and then bolt the rear of the tunnel between effectively 2 pieces of rubber as a sandwich? Or should I have 2 studs back there instead?
Standard Interstate tank mounting is two studs at the front with thick rubber washers between tank bottom and mounting bracket (3 or 4 usually , depending on thickness of rubber padding between tank tunnel and top frame tube) , and two bolts at the rear through the steel strap running under frame member. The slot in the strap is for adjustment and alignment so that both tapped holes in tank rear underside line up with bolts.
I have both Mk1a and Mk3 850’s which both have identical tank mounting arrangements as described above.
Thanks, that maintains my belief that this veteran is very unmolested, and perhaps the AN pictures are at variance to what is actually used.
I’ll base my rebuild on how it was when I dismantled it. but I’ll add fresh rubbers to maintain the clearances
My MK2A (built September 1973, so nominally a '74?) has studs, plain nuts and spring washers at the rear, not bolts. Plus the steel strap with ribbed rubber pad between the studs. This is as illustrated by AN and in – or perhaps I should say 'from' – the 1973 parts book 065988: I don't have an illustrated book for 1974, and I seem to remember mention that there wasn't one …? But I have the 1974 book with no illustrations, and I note that two studs and two 'rear bolts' are listed there. Looking closely at this area of the 1973 parts book (Group 28), there are a few things at variance between the illustrations and the listings, enough to drive you … nuts. Norton making it up as they went along, again? Anyway using studs means that the threads in the tank don't wear out; but having bolts at the rear might indeed be original, per the parts books. HTH
The one thing that most owners do wrong is to over-tighten the front mountings; this can lead to pulling the threaded bosses out of the tank [they are only held in place very lightly]. There should be three or four rubber washers on each of the front studs. Mount the tank on the frame mounting. Then add another rubber washer. Then the large steel washer, followed by the small washer and then the nyloc nut. When tightening the nyloc nut you need only to reach the nylon threads - finger-tight will be fine here - some movement of the tank will not create a problem. At the rear, there are bolts and the strap, which should have a rubber block where it meets the frame. You can probably do without the rear mountings completely, as the petrol pipes and front mountings will keep the tank in the correct location for most uses of the machine. Always have plenty of rubber between the tank and the frame; an old inner tube, correctly cut up, will be fine in this location. Good Luck!
My MK2a, nov 73 build is with bolts at the back of the tank, maybe they had 2 tank suppliers as they had 2 frame suppliers and the difference is the studs vs bolts. The tank came with the bike is early 80's so is likely original and not a replacement.
Mine is also a 9 73 build - I’ll tend towards Colin’s and John’s advice as that’s how I undid mine, I’m concerned I may struggle with clearance reassembling with fat fingers.
You start with one bolt loosely screwed into the tank, put the tank on the bike and then push strap through under frame and engage the open end of the strap with the bolt on the tank. Then with the strap still loose put bolt through hole in strap and screw it into tank. You can now tighten both bolts.
I also have an interstate tank on my MK III, having installed a pcv valve requiring extra breather tube above the airbox I found fitting the rear strap even more of a pita than usual, hurling a stream of invective at the the problem I had an epiphany.
I fit my strap from the battery side & opened the hole for the bolt with a dremel to form a slot on the right hand (rearward facing) side, I now fit the tank with both bolts in situ; slide the fixing strap onto the bolt over the oil tank and then use that as a pivot to slot the strap over the battery side bolt, then tighten the bolts.
It's easier to pivot the strap towards the rear, rather than towards the handlebars because of the seam on the bottom of the tank just in front of the seat restricts working space. I should have done this years ago, it's so much easier!
Mk III ES
Mike - sounds like an eureka! moment there. Thanks, I’ll have a good look at that option, along with John’s.
I did away with the stack of rubber washers years ago. I replaced them with two of the exhaust mounting rubber 'cotton reels', which are the same thickness as the rubber washers and give ample clearance. There's also no chance of the stud pulling out or going through into the tank. You then put a penny washer under the frame bracket and a plain nut, NOT A LOCKNUT.
I use the exhaust/headsteady buffers too, but I still use the single rubber washer under the penny washer and the nyloc nut. You can't have too much protection against vibration.
Today I tried this method out. A couple of minutes with a hacksaw and a file and I’d created what you said about. It was so simple in practice to fit the strap I’m amazed it wasn’t an original fitment doing it this way. It’s not as if it’s a structural component, solely there to limit movement.