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LH Crankase Repair
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Highfield
Epsom, Surrey
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September 21, 2020 - 10:42 am
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Hi All

I have been cracking on with my 1966 D7 restoration and split the engine this weekend. However, once I got it all stripped down I've noticed a bit of a botch job on the left hand crankcase at the drain plug. What looks to have happened is the original drain plug bolt has seized in the thread and someone in the past has drilled and tapped a new drain plug hole next to the old one, but they haven't made a very good job if it - see the pictures below.

IMG_4537-4.JPG

IMG_4538-2.JPG

IMG_4540-2.JPG

My questions are therefore, whats the best way to repair this? I've had a few thoughts as follows:

1) Get the hole welded up, drill out the old bolt and re-tap. I think this option would need to be done in an professional engineering workshop as the casing will need to be held firmly static to drill out the steel bolt and not into the softer surrounding aluminum. My other worry would be distortion from any welding as it is close to the mating face. Also, does anyone know a company who would take such a job on?

2) Leave it as it is and use heat resistant silicone sealant when replacing the drain plug. This is on the understanding that the silicone sealant will need to be reapplied every time the drain plug is removed and is a possible oil leak source.

3) Use an epoxy metal putty to build up the bossed area of the crankcase and re-tap. My concerns here are that the putty may just fall off, (good old gravity!), and again it would be a leak source in the engine.

I'd like to repair rather than replace the crankcase. It is my understanding that it is ill-advised to use crankcase halves from different engines. Is this the case?

Any advice on ways to tackle this issue is greatly appreciated.

Highfield

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BonesCDI
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September 21, 2020 - 11:46 am
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I repair case damage like this a lot.

I'd go the option of removing the remnants of the old drain plug, re weld the hole, re-machine, drill and tap new hole.

I'm sure there are specialist in the UK who could do this easily.

I'd not be too worried about distortion...…...just bolt both cases together when welding.

regards,

 

Bones

Running and project bikes from 1912 -2005..........She hasn't said stop yet.........

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sunny
Norfolk
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September 21, 2020 - 11:53 am
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hi Greg  that  was a  realy   poor  job  done   the  1 st  time  around   as it  could  have  left  some metal   to drill out  the  old stump  &  retap   anything

uther  than    aloy   welding    may   brack away   so  id   drill  out  the  1/4 " stump   & get  the  big  hole  aloy welded  up  the   welder  chap  mite 

need  a serport   inside    or  a bit  shaped  in a lath  to fit   coz the heat mit  be to much    a  good  project   it  macks  you  think   a    

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Highfield
Epsom, Surrey
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September 27, 2020 - 6:40 pm
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Hi Sunny and Bones and thanks for the replies.

As you both advised I'm getting the crankcase welded up to make a proper repair.

It's not something I'm geared up to do at home so I've gone the FD Motorcycles in Essex to do the repair, they are in the Good Blokes Guide.

As the cylinder barrel needed a rebore they are doing that as well 🙂

I'll post a picture or two of the repair when I get it back.

Cheers

Greg

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Highfield
Epsom, Surrey
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October 21, 2020 - 1:18 pm
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I've just picked up the crankcase after getting it repaired by FD Motorcycles. I think they've done a really good job of the weld repair and provided a new bolt and copper washer too!.

IMG_4657-v2.JPG

IMG_4658-v3.JPG

Greg

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Stoo63
GLASGOW
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October 21, 2020 - 2:33 pm
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Good stuff, Greg. Just out of interest, how much does a repair lie that cost? I'm sure loads of us have little bit and bobs we'd love tidied up - costs permitting 🙂

 '55 D3 Battery; '58 Square Four (project); '59 D1 direct lighting plunger; '59 Tiger Cub; '60 5TA;  '76 FS1-E; '91 GTR 1000;  '97 Honda Sky SGX50.

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sunny
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October 21, 2020 - 3:19 pm
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a  2nd  hand  case   probly  around    £ 20     so       its   a  grate  job    wat  ever  you payed   

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Number6
Lincolnshire
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October 21, 2020 - 4:45 pm
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http://livinginthepast-audioweb.co.uk/imagex/misc/th_thumbsup.gif

Mike H --

Murphy's 4th law of motion states that any small object that is accidentally dropped will immediately hide itself under a larger object.

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Highfield
Epsom, Surrey
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October 21, 2020 - 4:56 pm
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I got some other work done at the same time, (barrel re-bored to +40, new piston, new con rod, big end and little end fitted), so I didn't get an itemised invoice I'm afraid.

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Stoo63
GLASGOW
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October 21, 2020 - 5:09 pm
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Aha, hopefully you'l be good to go now, Greg 🙂

 '55 D3 Battery; '58 Square Four (project); '59 D1 direct lighting plunger; '59 Tiger Cub; '60 5TA;  '76 FS1-E; '91 GTR 1000;  '97 Honda Sky SGX50.

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Highfield
Epsom, Surrey
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October 22, 2020 - 8:53 pm
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Yes, I'm looking forward to my first Bantam engine rebuild! 🙂

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