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Ali head gasket blown
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Danny
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January 29, 2020 - 5:03 pm
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Whilst running in my fully rebuilt B175 after 30 pleasant miles come to start it today and it's blown the head gasket ( the thick trials one).

One of the nuts holding the cylinder head has stripped so whilst the head is off I've put a metal ruler across the holes the stud goes through and it's not perfectly flat. 

I'm going to try and flat it with the glass and wet and dry job , Any advice? I also remember Howard saying even new gaskets need annealing using the soap method ? I never did that and I couldn't find my torque wrench so probably overtightened the cylinder head 🙄

Best way of annealing Ali ? Does it have to go straight on or be o.k left a day after.

This bike is a real learning curve 😂

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bantammad
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January 31, 2020 - 8:49 am
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Hi bantammad ere Hi Danny just a point can l suggest you replace the long barrel studs and nuts . I suspect the ones you have the threads are stretched.. As note I use studs half inch longer same with the nut length cures most head leak problems hope it helps have fun Les 

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chickensoup
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January 31, 2020 - 9:03 am
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Hi Danny,

There's some good video clips on youtube showing how to anneal Aluminium, using ordinary soap and a blow torch.

Nick

1950 BSA D1 Plunger   242 UYW

1966 BSA D7  LBF 62 D

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bantammad
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January 31, 2020 - 9:22 am
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Hi bantammad ere chickensoup spot on good advice have fun Les 

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Danny
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January 31, 2020 - 9:14 pm
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bantammad said
Hi bantammad ere Hi Danny just a point can l suggest you replace the long barrel studs and nuts . I suspect the ones you have the threads are stretched.. As note I use studs half inch longer same with the nut length cures most head leak problems hope it helps have fun Les   

Good point well made just wish I seen it before putting bike back together ! You maybe right I think it's sealed this time so far but I did have to go tighter than I would of liked so will price up new studs and nuts 👍

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Danny
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January 31, 2020 - 9:17 pm
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chickensoup said
Hi Danny,

There's some good video clips on youtube showing how to anneal Aluminium, using ordinary soap and a blow torch.

Nick  

I'll take a peak 👍

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AdrianS
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February 1, 2020 - 1:43 pm
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You can use wet and dry to flatten the head but the method I prefer is to use a thickish piece of glass with valve grinding paste on it. Use the thick paste first then the thin paste and wash the head thoroughly after.

Good advice re changing head studs. I had problems with a D7 in the 70's with head gaskets blowing. Turned out that someone had replaced 1 stud and left the other 3 in place. all expanded differently when hot and blew head gasket.

You can anneal the ali gasket. However it will probably have been compressed when tightening and after annealing will compress even more.

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Blue Heeler
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February 1, 2020 - 2:15 pm
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 Re annealing gasket, you could do a before & after using vernier calipers. I would check gasket either side of each stud hole, plus centre of each side...12 places.

Blue

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nickjaxe
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February 1, 2020 - 8:39 pm
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If your stuck for a thick piece of glass to use as a flat plate...most kitchen worktops are usually quite flat.

Being soft the ali is soon flat...I just lay a sheet of wet dry paper on my flat plate...and lube it with WD40.

Think last time I used 240 grade..

Those head nut are not done up to tight...cant remember the torque of the top of my head but I'm sure you know it anyway.

Nick.

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thornebt
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February 2, 2020 - 8:46 am
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nickjaxe said
If your stuck for a thick piece of glass to use as a flat plate...most kitchen worktops are usually quite flat.
Being soft the ali is soon flat...I just lay a sheet of wet dry paper on my flat plate...and lube it with WD40.
Think last time I used 240 grade..
Those head nut are not done up to tight...cant remember the torque of the top of my head but I'm sure you know it anyway.
Nick.  

If you are going to use your kitchen worktop and grinding paste it might be worth checking with the other half first that it is ok. Cheers. Bruce.

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Danny
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February 2, 2020 - 9:31 am
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Cheers people,

As it's only done 50 miles from the new build and I didn't radius or check the ports I'm gonna pull top end off check the ports ( is it a case of just filing them ? I'll have a Google ) then fit new studs and nuts and a new gasket.

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cocorico
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February 2, 2020 - 9:57 am
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Danny said
... check the ports ( is it a case of just filing them ? I'll have a Google )...

You just need to take any sharp edges off, ie a small radius. You can use a fine file or small grindstone on a Dremel-type tool. Make sure you wash out any dust produced after.

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

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Danny
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February 2, 2020 - 10:57 am
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cocorico said

Danny said
... check the ports ( is it a case of just filing them ? I'll have a Google )...

You just need to take any sharp edges off, ie a small radius. You can use a fine file or small grindstone on a Dremel-type tool. Make sure you wash out any dust produced after.  

Cheers 👍

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February 2, 2020 - 11:01 am
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thornebt said

If you are going to use your kitchen worktop and grinding paste it might be worth checking with the other half first that it is ok. Cheers. Bruce.  

Quick google image search off your avatar confirms that`s Kylie...I`m more a Britney sort of chap, and she says not only will she let me, she`ll help  too 😉

Danny, if it feels like you could cut your finger on a port, then there`s a chance it`ll chop your rings up. You want just enough lead-in so your rings can nicely whiz past the ports without being chopped.

Blue

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nickjaxe
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February 2, 2020 - 1:32 pm
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thornebt said

If you are going to use your kitchen worktop and grinding paste it might be worth checking with the other half first that it is ok. Cheers. Bruce.  

Indeed...I learnt that many years ago...but she goes the hairdressers on a Friday morning....usually their best part 2 hours.

Me not silly.

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bantammad
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February 2, 2020 - 6:24 pm
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Hi bantammad ere that sounds a bit risky using the kitchen work top , bad as boiling a tin of link life on the cooker to lube the chain do that at the same time might liven things up a bit.? Regards Les 

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SpacedMarine
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February 2, 2020 - 8:21 pm
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I heated a set of crankcase up in the oven once ....... 🤣🤣🤣

What's 7/16 in mm again?

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nickjaxe
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February 2, 2020 - 10:03 pm
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Been there got the tea shirt...have you frozen bearings in the freezer though?

My Bantam video              https://www.you.....jpOFmzRZRI

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bantammad
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February 2, 2020 - 10:10 pm
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Hi bantammad ere yessir I’ve got the other T/ shirt have fun Les 

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nickjaxe
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February 2, 2020 - 10:17 pm
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Wear it with pride.

My Bantam video              https://www.you.....jpOFmzRZRI

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