Author Topic: B31 help  (Read 660 times)

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DEDGE

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B31 help
« on: 28 July, 2017, 15:20:50 »
Hi Guys
Can anyone give me some technical advice please? I have a 1950 B31 which I am trying to renovate and started to take the engine apart. Taking of the cylinder head there was a thick head gasket, I did not think there was one, can you tell me if they are the right parts. Iron head and cylinder casting No on head66-1157, casting No on cylinder 65-1703 or could be 66-1793 or the 66 could be 65. And worst news on the inside of the cylinder liner, timing side and 2 deep groves about the width of the gudgeon diameter I take these are not meant to be there. I f the liner is gone can theses still be got or repaired. I live in Dorset
Best Regards
Dedge

DEAN SOUTHALL

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Re: B31 help
« Reply #1 on: 28 July, 2017, 17:09:36 »
Draganfly don't list a head gasket for the B31 so I am assuming it (oddly) doesn't use one. Sorry I can't be more definate (Julian will confirm one way or the other later I am sure).

Sounds like gudgeon pin grooves in the bore. Not a problem except for the pocket. If a re-bore won't remove them then a reline will and is readily available for around £120.

Good luck.

JulianS

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Re: B31 help
« Reply #2 on: 28 July, 2017, 20:07:56 »
No head gaskets fitted on B31 or B33 just metal to metal.

65 1157 is a casting number, the number for a machined up to 1953 B31 (ZB31 engine number) head is 65 1156.

65 1703 is the part number for a B31 cylinder 1954 (BB31 engine number) season on which had bigger fins than the earlier one.

B31 pistons available up to  plus 60, liners also available - internet search will show that together they would cost aroung £190 plus vat plus fitting.

Might be worth considering finding a better cylinder - remember autojumble at Sammy Millers museum on 6 August and a bigger one at Bath and West show ground Shepton Mallet on 12 August. 

ANDY HIGHAM

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Re: B31 help
« Reply #3 on: 28 July, 2017, 20:59:50 »
If the bore is gone past the maximum rebore size you can use a Triumph T140 piston, it is 76mm and gives a capacity of around 400cc

MickB32

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Re: B31 help
« Reply #4 on: 29 July, 2017, 07:39:51 »
funnily enough my b31 is running a head gasket.now blowing slightly so a job for winter let you know if  i find anything strange or enlightening.cheers mick

DEDGE

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Re: B31 help
« Reply #5 on: 29 July, 2017, 15:40:40 »
Hi Guys
Thanks for the replies and the information. It looks like the engineering work on my engine may be more than I am capable off , if thatís the case can anyone recommend some ware or someone who could do this. Also on removing  the rocker oil feed banjo bolts I found that they have a large hole the same as the return one could this be a later modification or has someone just fitted the wrong ones.
Thanks again
Dedge

BEEZARAY

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Re: B31 help
« Reply #6 on: 29 July, 2017, 15:52:57 »
Hi If you need a barrel I have one on 40" for sale! give me shout on the forum. Ray

om15

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Re: B31 help
« Reply #7 on: 29 July, 2017, 17:39:54 »
I can recommend this place.

http://www.g-c-s-motorcycles.co.uk/

Jed overhauls and repairs classic bike engines, I had a small job done there on my C15 head and he showed me his various jobs in hand, nice bloke, sensible price and top quality.
If you go into the estate, Three Cross Triumph is on your right, take the next right and he is on the right hand side of the lane.

Edit, if you are at the other end of Dorset you could speak to Andy in Bridport, he carried out a tricky repair on my Adventurer a few years ago, did a good job

http://www.awsbikerepair.com/
« Last Edit: 29 July, 2017, 17:54:52 by om15 »

DEDGE

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Re: B31 help
« Reply #8 on: 31 July, 2017, 20:51:15 »
Hi Guys
Thanks for the replies But I am afraid I still need help. How can I tell if my cylinder head is the right one (1950) is there a part number stamped on it or what does it look like compared to the post 1953 one, also the comparison of the cylinder.
On the top of the cylinder is a spigot that goes in a register on the cylinder head this fits ok but the other two machined surfaces where the threads are on the cylinder head and the loose bolt holes on the cylinder do not meet any ideas
Sorry to be a pain
Dedge

JulianS

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Re: B31 help
« Reply #9 on: 31 July, 2017, 20:59:04 »
Please post photos of what you have. Someone maybe able to help.

DEDGE

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Re: B31 help
« Reply #10 on: 01 August, 2017, 22:05:48 »
Hi Guys
Pictures to go with the previous words 3 of the cylinder head and 1 of the cylinder. Julian said the cylinder number denotes a 1953 cylinder (should be 1950),.
Thanks everyone for your help
Dedge

Greybeard

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Re: B31 help
« Reply #11 on: 01 August, 2017, 22:53:59 »
Hello, Dedge.
I have a 1953 B31 (plunger sprung 52/53 spec jobbie) and your head and barrel look familiar to me. For what it's worth, I believe that there should be a gap, albeit a very small one between the flat surfaces you describe and that the seal proper is made by the circular machined surfaces. That small gap ensures that the circular surfaces will mate together tightly. I know the service sheets indicate that it's a dry joint but I do use a light smear of that truly marvellous jointing compound, Wellseal  :D

Steve

Steve from East Yorkshire - Not the Greybeard of the A7/A10 forum who was not actually registered on this one when I signed up ;-)

JulianS

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Re: B31 help
« Reply #12 on: 02 August, 2017, 15:22:30 »

DEDGE

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Re: B31 help
« Reply #13 on: 03 August, 2017, 19:22:16 »
Hi Guys
Thank you all very much for your help and advice
Dedge