Author Topic: B40 MkI seat mounting  (Read 500 times)

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Mike40M

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B40 MkI seat mounting
« on: 15 February, 2020, 17:53:26 »
I found that PO had fitted the seat in a highly unconventional way. To get it off, I had to remove rear fender, air filter box and oil tank.
So a better way to fasten the seat seems like a good idea. Can't find out how it was made at BSA.
Anybody can help by explaining how it should be? A picture or two would help.

berniej

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Re: B40 MkI seat mounting
« Reply #1 on: 15 February, 2020, 18:50:32 »
https://www.draganfly.co.uk/bsa/bsa/b40/category/1217-1961-65-tank

Front lugs on seat locate onto a frame crossbar and rear bracket drops onto the bolts that secure the upper shock mounts.

Cheers,
Bernie
'49 M21/B31 hybrid
'56 M21 combination
B40 Super Star
A50CC project

Mike40M

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Re: B40 MkI seat mounting
« Reply #2 on: 16 February, 2020, 12:51:25 »
Thanks though the link refers to the earlier model frame. Sadly, there is no crossbar on my frame. Some vandal also removed the tank bracket. On  the bottom there is nothing except some threaded holes. I guess the best way to go is to make an U-formed bracket with a slot and attach it to the saddle. Then making a horizontal cross bar, somehow attach it to the frame. This would solve the front mounting. The rear will be much easier. Making a bracket for the tank holding screw and fix it on the frame will be a bit trickier.
Can't understand why some people abuse frames with hacksaws and angle grinders. Should be needed a licence with background check for buying those items.

chaz

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Re: B40 MkI seat mounting
« Reply #3 on: 16 February, 2020, 18:38:59 »
Mike40M, sounds like a common thing, our B40 was a flat track racer in AMerica, fitted with a mustang tank now has the centre tank fixing bracket removed so will either have to make a new one and weld on or make some sort of adaptor to clamp on the spine.

Mike40M

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Re: B40 MkI seat mounting
« Reply #4 on: 23 February, 2020, 15:49:21 »
Chaz, read  that you are thinking of welding on a tank lug. I found a way to attach a lug without welding it on the frame. After a lot of thinking, I found a simple solution. Cut a 2.5" piece of a 38mm ( 1 1/2" ) exhaust pipe. Cut it in halves. Put one half on the frame tube. Use two jubilee clips to hold it on the frame.
Sorry, has not yet figured out how to fix the bolt to the pipe half.

chaz

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Re: B40 MkI seat mounting
« Reply #5 on: 23 February, 2020, 17:17:57 »
Mike, Im thinking of a piece of sheet 1/16th thick and shaped as original and then two slots in the arms for a jubilee clip to go through to hold onto the spine tube, maybe the plate might not be thick enough, I would brace the two down pieces, failing thatits mill up a block of ally but still have to jubilee to frame. Ive checked the '65 parts book and ours has the bracket at the bottom end of the spine and a bolt on back end so presumably the earlier one.
the original frame we had was the flat tracker 1964 and had the front lower tank bracket removed, I originally posted a request for dimensions of it, unfortunately that frame is still trying to be straightened and therefore we have bought a replacement frame to use incase the other has to be scrapped, this later frame , also swan necked has the upper tank bracket removed so as both were originally American imports it must be a thing they do over there.

Mike40M

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Re: B40 MkI seat mounting
« Reply #6 on: 23 February, 2020, 18:22:04 »
Update. After some more thinking, I decided to make a quickie. Just welded a nut on top of the halfpipe. A right length of threaded bar. Counter nut on the bar. Fitted the tank. Piece of cake. A little wiggling of the tank to get it right. Finally tightened the jubilee clips. Easy if the clip screws are on the bottom and slightly inclined.
Test did go so well, I'll keep it like that.
Did not mention that inner diameter of the exhaust pipe is 35mm, same as frame tube o.d.