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Crankshaft oil seals
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Gnome60
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January 15, 2020 - 7:50 pm
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OK so this is probably an old chestnut but which way round should the crankshaft oil seals be fitted? Spring side towards the crankshaft or the other way round? Also, when the piston is at TDC how far below the top of the barrel will the crown of the piston be on a D7?

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Stoo63
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January 15, 2020 - 8:00 pm
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Info here ** Please log in to view **

And much more here ** Please log in to view **

This thread on TDC reappeared a couple of days a go...  ** Please log in to view **

And a mountain of info here on the subject ** Please log in to view **

Hopefully something in there will sort out your probs 🙂

Stewart

'52 D1 direct lighting plunger, '58 Square Four (project), '59 D1 direct lighting plunger,  '59 Tiger Cub, '60 5TA,  '76 FS1-E

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Gnome60
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January 15, 2020 - 10:01 pm
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Thanks for clarifying about oil seals. My query about the position of the piston when at TDC is because it seems to reach to about 2mm below the top of the cylinder bore. Should there be a gap like this? I'm asking because following a rebuild the motor wouldn't run properly. I've tried all other angles such as carb and spark so have gone back to the beginning again and stripped the motor down.

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sunny
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January 16, 2020 - 5:02 pm
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Blue Heeler
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January 17, 2020 - 1:07 am
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Gnome60 said
......My query about the position of the piston when at TDC is because it seems to reach to about 2mm below the top of the cylinder bore. Should there be a gap like this? .....

What I remember from rebuilding my D7s, that`s correct. I have spare engines laying about, there`s bound to be one with its head off, if you`d like a photo emailing. Can`t post pics on here until I junk Vista.

Regards

Blue

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chickensoup
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January 18, 2020 - 1:59 pm
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Hi,

One of the good point about Ebay, is that you have another good photo base. If you can't find it on our site, there's probably a photo of it on EBay.

Photo's commonly show a wear band on the barrel up to about 2mm from the top of the barrel. The barrel, con- rod and piston are pretty much standard items and the TDC point is fixed due to the length of the con rod, height of barrel and piston dimensions etc.

I would say your 2mm band is correct.

Nick

1950 BSA D1 Plunger   242 UYW

1966 BSA D7  LBF 62 D

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bantammad
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February 4, 2020 - 10:31 am
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Hi bantammad ere can I stick my five pee in interestingly the wear mark approximately two mill from the top facing off the barrel is made by the top ring at tdc.the piston should be flush to the barrel top face, a point to note is how thick is the base gasket being used as you may have one of the wrong thickness just a thought have fun Les 🏍

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