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Bantam D1 Left side crank seal replacement
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JustinW
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February 22, 2020 - 7:53 pm
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Oh dear. I put the engine all back together after fitting new seals etc and been out for a spin. Not good. Seems I caught the generator side (left) crank seal as I refitted the crankshaft. Oil coming through to generator side and lack of power etc. You can see the bit I caught at the bottom.

Do I have to split the engine again to replace this seal? It looks semi-feasible to do it as it fits from outside. Anyone done this seal from the outside?

thanks

IMG_9943.jpg

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cocorico
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February 22, 2020 - 7:55 pm
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Yes, I've done it on a D3. The hardest bit is removing the old seal.

1956 D3 running, lights to sort. 7 other bikes in the Barn. 1950 D1 engine being rebuilt (slowly).

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Blue Heeler
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February 22, 2020 - 7:58 pm
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Hard luck Justin 🙁

You have a bit of a burr you may want to remove.

Your seal appears to be a fair way in, I have mine flush.

It is in the correct way around?

You can carefully winkle that out without any stripping...quick job it is. Self-tapping screws equidistant. Pull out...hopefully.

New seal, cheap enough

Blue

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JustinW
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February 22, 2020 - 8:05 pm
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Thanks guys that's a huge relief. I've removed the little scrap of seal which came through from other side. It is the right way round, I think it's just the lighting. Lips are facing the crank.

Looking at a different angle, it seems I might be able to simply press another seal behind this one. Can't hurt can it?side-view.jpg

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Blue Heeler
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February 22, 2020 - 8:12 pm
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Whoops, Cocorico snuck in there while I was scribbling.

Ok yes correct fitment, trick of the light then.

I would not endorse doubling up, what if debris from damaged seal gets spinning up between the two....but then I am a fussy so-and-so.

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JustinW
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February 22, 2020 - 8:24 pm
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Yes, you're right, I'll use the self tapper trick to pull it out.

Disappointed wasn't the word today, new crankshaft, new piston, new seals, and had to get off and push it on a very steep part of a hill!! Glad I found what the problem was. Lesson learnt!

Mind you, I did set my personal D1 land speed record of 36mph downhill. I'll see if I can make 40mph with seal fixed.

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Blue Heeler
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February 22, 2020 - 8:38 pm
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JustinW said
Yes, you're right, I'll use the self tapper trick to pull it out.

Disappointed wasn't the word today, new crankshaft, new piston, new seals, and had to get off and push it on a very steep part of a hill!! Glad I found what the problem was. Lesson learnt!

Mind you, I did set my personal D1 land speed record of 36mph downhill. I'll see if I can make 40mph with seal fixed.  

What, not running her in 😉

You blueprint your engines like me?

At least you`ve had her running...that`s progress in any Bantam rebuilders world. I`m always pleasantly surprised when I fire one up after a rebuild, as if it`s some sort of magic 🙂

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wildun
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February 22, 2020 - 10:20 pm
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yes, the chaps are correct, screw two self tappers into the seal then pull it out. When you fit the replacement, tap it in gently and evenly but only just far enough so that the seal lip is located on the wider diameter of the crank, no more. Your first effort, the seal was too far in.

1951 Bantam D1 125, 1954 Bantam Enduro 125, 1970 Bantam B175, all Bantams on the road and ridden regularly, 1995 Yamaha Diversion 900 and 2016 Honda Integra 750 scooter. Horses for courses, all very different to each other, but a bike for every occasion.

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JustinW
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February 23, 2020 - 2:53 pm
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Thumbs up, seal removed using screws. New one on order. This one was well messed up, glad I took it out. Thanks.

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