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90-817 piston
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jolon1
Leigh Lancashire
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May 11, 2019 - 7:28 pm
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I've just bought a piston off fleabay, hoping it was for a D7. The con-rod is with it and as far as I can see, it's not on a needle roller bearing. The stamp on the top is, 90-817 but I can't find any reference.The con-rod has a casting number 90-487 but I can't find any reference for this either. Any ideas wil be greatly apreciated.  bow

D7 & D1 Racer

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mike p5xbx
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May 12, 2019 - 12:04 am
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Conrods read the bottom of this page
draganfly.co.uk
** Please log in to view **

D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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jolon1
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May 12, 2019 - 11:58 am
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Thanks, Mike. I'll see what I can find from that. I was just wondering mainly for the number on the piston.

D7 & D1 Racer

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cocorico
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May 12, 2019 - 12:20 pm
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Have you tried a search? bsa piston 90-817 site:bsabantamclub.com/forum in your browser query box.

Looks to be for a D3.

EDIT - struck out my error, sorry for that.

1956 D3 running, lights to sort. 7 other bikes in the Barn, including a Morini 250 now insured and on road testing.

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mike p5xbx
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May 12, 2019 - 5:21 pm
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90-817 does seem to be for a D3 but that has a 57mm bore
D7 is 61.5mm so should be obviously wrong
if your piston is 61.5+ with a flat top and 3ring it should fit a D7 as long as the gudgeon pin hole is the same size as the conrod small end hole
Piston to bore clearance at bottom of skirt is 0.004”min-0.010”max

D? - D10- D14 Bantams 350 AJS -500 Triumph http://bsanotru.....lfire.com/

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jolon1
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May 12, 2019 - 6:42 pm
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cocorico said
Have you tried a search? bsa piston 90-817 site:bsabantamclub.com/forum in your browser query box.

Looks to be for a D3.  

I did coco, but nothing came up.

D7 & D1 Racer

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jolon1
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May 12, 2019 - 6:48 pm
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You are right, Mike. It is 57mm ,flat top and 2 rings.

D7 & D1 Racer

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cocorico
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May 12, 2019 - 8:32 pm
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Oops - I must have had a senior moment. What I did was to put 'bsa piston 90-817' in my browser - bingo!

Will edit my errors...

1956 D3 running, lights to sort. 7 other bikes in the Barn, including a Morini 250 now insured and on road testing.

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